==== Hot Rod Protocol
The following articles provides detailed information about each version of
the custom TCP client/server Hot Rod protocol.

* link:#hot_rod_protocol_1_0[Hot Rod Protocol 1.0]
* link:#hot_rod_protocol_1_1[Hot Rod Protocol 1.1]
* link:#hot_rod_protocol_1_2[Hot Rod Protocol 1.2]
* link:#hot_rod_protocol_1_3[Hot Rod Protocol 1.3]
* link:#hot_rod_protocol_2_0[Hot Rod Protocol 2.0]
* link:#hot_rod_protocol_2_1[Hot Rod Protocol 2.1]
* link:#hot_rod_protocol_2_2[Hot Rod Protocol 2.2]
* link:#hot_rod_protocol_2_3[Hot Rod Protocol 2.3]
* link:#hot_rod_protocol_2_4[Hot Rod Protocol 2.4]
* link:#hot_rod_protocol_2_5[Hot Rod Protocol 2.5]
* link:#hot_rod_protocol_2_6[Hot Rod Protocol 2.6]
* link:#hot_rod_protocol_2_7[Hot Rod Protocol 2.7]

===== Hot Rod Protocol 1.0

.Infinispan versions
TIP: This version of the protocol is implemented since Infinispan 4.1.0.Final

IMPORTANT: All key and values are sent and stored as byte arrays. Hot Rod
makes no assumptions about their types.

Some clarifications about the other types:

* vInt : Variable-length integers are defined defined as compressed,
positive integers  where the high-order bit of each byte indicates whether
more bytes need to be  read. The low-order seven bits are appended as
increasingly more significant bits in the resulting integer value making it
efficient to decode. Hence, values from zero to 127 are  stored in a single
byte, values from 128 to 16,383 are stored in two bytes, and so on:
+
[options="header"]
|==============================================================================
| `Value`     | `First byte`    | `Second byte`     | `Third byte`

| `0`         | `00000000`      |                   |
| `1`         | `00000001`      |                   |
| `2`         | `00000010`      |                   |
| `...`       |                 |                   |
| `127`       | `01111111`      |                   |
| `128`       | `10000000`      | `00000001`        |
| `129`       | `10000001`      | `00000001`        |
| `130`       | `10000010`      | `00000001`        |
| `...`       |                 |                   |
| `16,383`    | `11111111`      | `01111111`        |
| `16,384`    | `10000000`      | `10000000`        | `00000001`
| `16,385`    | `10000001`      | `10000000`        | `00000001`
| `...`       |                 |                   |
|==============================================================================
+
* signed vInt: The vInt above is also able to encode negative values, but will
always use the maximum size (5 bytes) no matter how small the endoded value is.
In order to have a small payload for negative values too, signed vInts uses ZigZag
encoding on top of the vInt encoding.
More details link:$$http://developers.google.com/protocol-buffers/docs/encoding#types$$[here]

* vLong : Refers to unsigned variable length long values similar to vInt but
applied to longer values. They're between 1 and 9 bytes long.
* String : Strings are always represented using UTF-8 encoding.

====== Request Header

The header for a request is composed of:

.Request header

[cols="3,^2,10",options="header"]
|==============================================================================
|Field Name           | Size       | Value

| Magic               | 1 byte     | +0xA0+ = request
| Message ID          | vLong      | ID of the message that will be copied
back in the response. This allows for hot rod clients to implement the
protocol in an asynchronous way.
| Version             | 1 byte     | Infinispan hot rod server version.
In this particular case, this is +10+
| Opcode              | 1 byte     | Request operation code: +
+0x01+ = put (since 1.0) +
+0x03+ = get (since 1.0) +
+0x05+ = putIfAbsent (since 1.0) +
+0x07+ = replace (since 1.0) +
+0x09+ = replaceIfUnmodified (since 1.0) +
+0x0B+ = remove (since 1.0) +
+0x0D+ = removeIfUnmodified (since 1.0) +
+0x0F+ = containsKey (since 1.0) +
+0x11+ = getWithVersion (since 1.0) +
+0x13+ = clear (since 1.0) +
+0x15+ = stats (since 1.0) +
+0x17+ = ping (since 1.0) +
+0x19+ = bulkGet (since 1.2) +
+0x1B+ = getWithMetadata (since 1.2) +
+0x1D+ = bulkGetKeys (since 1.2) +
+0x1F+ = query (since 1.3) +
+0x21+ = authMechList (since 2.0) +
+0x23+ = auth (since 2.0) +
+0x25+ = addClientListener (since 2.0) +
+0x27+ = removeClientListener (since 2.0) +
+0x29+ = size (since 2.0) +
+0x2B+ = exec (since 2.1) +
+0x2D+ = putAll (since 2.1) +
+0x2F+ = getAll (since 2.1) +
+0x31+ = iterationStart (since 2.3) +
+0x33+ = iterationNext (since 2.3) +
+0x35+ = iterationEnd (since 2.3) +
+0x37+ = getStream (since 2.6) +
+0x39+ = putStream (since 2.6) +
| Cache Name Length   | vInt       | Length of cache name. If the passed
length is +0+ (followed by no cache name), the operation will interact with
the default cache.
| Cache Name          | string     | Name of cache on which to operate.
This name must match the name of predefined cache in the Infinispan
configuration file.
| Flags               | vInt       |  A variable length number representing
flags passed to the system. Each flags is represented by a bit. Note that
since this field is sent as variable length, the most significant bit in a
byte is used to determine whether more bytes need to be read, hence this bit
does not represent any flag. Using this model allows for flags to be combined
in a short space. Here are the current values for each flag: +
+0x0001+ = force return previous value
| Client Intelligence | 1 byte     |  This byte hints the server on the client capabilities: +
+0x01+ = basic client, interested in neither cluster nor hash information +
+0x02+ = topology-aware client, interested in cluster information +
+0x03+ = hash-distribution-aware client, that is interested in both cluster and hash information +
| Topology Id         | vInt       | This field represents the last known
view in the client. Basic clients will only send 0 in this field.
When topology-aware or hash-distribution-aware clients will send 0 until they
have received a reply from the server with the current view id.
Afterwards, they should send that view id until they receive a new view id
in a response.
| Transaction Type    | 1 byte     | This is a 1 byte field, containing one
of the following well-known supported transaction types (For this version of
the protocol, the only supported transaction type is 0): +
+0+ = Non-transactional call, or client does not support transactions.
The subsequent TX_ID field will be omitted. +
+1+ = X/Open XA transaction ID (XID). This is a well-known, fixed-size format.
| Transaction Id      | byte array |  The byte array uniquely identifying the
transaction associated to this call. Its length is determined by the
transaction type. If transaction type is 0, no transaction id will be present.
|==============================================================================

====== Response Header

The header for a response is composed of:

.Response header

[cols="3,^2,10",options="header"]
|==============================================================================
|Field Name           | Size       | Value

| Magic                  | 1 byte     | +0xA1+ = response
| Message ID             | vLong      | ID of the message, matching the request
for which the response is sent.
| Opcode                 | 1 byte     | Response operation code: +
+0x02+ = put (since 1.0) +
+0x04+ = get (since 1.0) +
+0x06+ = putIfAbsent (since 1.0) +
+0x08+ = replace (since 1.0) +
+0x0A+ = replaceIfUnmodified (since 1.0) +
+0x0C+ = remove (since 1.0) +
+0x0E+ = removeIfUnmodified (since 1.0) +
+0x10+ = containsKey (since 1.0) +
+0x12+ = getWithVersion (since 1.0) +
+0x14+ = clear (since 1.0) +
+0x16+ = stats (since 1.0) +
+0x18+ = ping (since 1.0) +
+0x1A+ = bulkGet (since 1.0) +
+0x1C+ = getWithMetadata (since 1.2) +
+0x1E+ = bulkGetKeys (since 1.2) +
+0x20+ = query (since 1.3) +
+0x22+ = authMechList (since 2.0) +
+0x24+ = auth (since 2.0) +
+0x26+ = addClientListener (since 2.0) +
+0x28+ = removeClientListener (since 2.0) +
+0x2A+ = size (since 2.0) +
+0x2C+ = exec (since 2.1) +
+0x2E+ = putAll (since 2.1) +
+0x30+ = getAll (since 2.1) +
+0x32+ = iterationStart (since 2.3) +
+0x34+ = iterationNext (since 2.3) +
+0x36+ = iterationEnd (since 2.3) +
+0x38+ = getStream (since 2.6) +
+0x3A+ = putStream (since 2.6) +
+0x50+ = error (since 1.0) +
| Status                 | 1 byte     | Status of the response, possible values: +
+0x00+ = No error +
+0x01+ = Not put/removed/replaced +
+0x02+ = Key does not exist +
+0x81+ = Invalid magic or message id +
+0x82+ = Unknown command +
+0x83+ = Unknown version +
+0x84+ = Request parsing error +
+0x85+ = Server Error +
+0x86+ = Command timed out +
| Topology Change Marker | string     | This is a marker byte that indicates
whether the response is prepended with topology change information.
When no topology change follows, the content of this byte is +0+.
If a topology change follows, its contents are +1+.
|==============================================================================

CAUTION: Exceptional error status responses, those that start with 0x8 ...,
are followed by the length of the error message (as a vInt ) and
error message itself as String.

====== Topology Change Headers
The following section discusses how the response headers look for
topology-aware or hash-distribution-aware clients when there's been a cluster
or view formation change. Note that it's the server that makes the decision on
whether it sends back the new topology based on the current topology id and
the one the client sent. If they're different, it will send back the new topology.

====== Topology-Aware Client Topology Change Header
This is what topology-aware clients receive as response header when a
topology change is sent back:

[cols="3,^2,10",options="header"]
|==============================================================================
|Field Name                                    | Size                     | Value

| Response header with topology change marker  | variable                 | See previous section.
| Topology Id                                  | vInt                     | Topology ID
| Num servers in topology                      | vInt                     |
Number of Infinispan Hot Rod servers running within the cluster.
This could be a subset of the entire cluster if only a fraction of those
nodes are running Hot Rod servers.
| m1: Host/IP length                           | vInt                     |
Length of hostname or IP address of individual cluster member that Hot Rod
client can use to access it. Using variable length here allows for covering
for hostnames, IPv4 and IPv6 addresses.
| m1: Host/IP address                          | string                   |
String containing hostname or IP address of individual cluster member
that Hot Rod client can use to access it.
| m1: Port                                     | 2 bytes (Unsigned Short) |
Port that Hot Rod clients can use to communicate with this cluster member.
| m2: Host/IP length                           | vInt                     |
| m2: Host/IP address                          | string                   |
| m2: Port                                     | 2 bytes (Unsigned Short) |
| ...etc||
|==============================================================================

====== Distribution-Aware Client Topology Change Header
This is what hash-distribution-aware clients receive as response header
when a topology change is sent back:

[cols="3,^2,10",options="header"]
|==============================================================================
|Field Name                                    | Size                     | Value

| Response header with topology change marker  | variable                 |
See previous section.
| Topology Id                                  | vInt                     |
Topology ID
| Num Key Owners                               | 2 bytes (Unsigned Short) |
Globally configured number of copies for each Infinispan distributed key
| Hash Function Version                        | 1 byte                   |
Hash function version, pointing to a specific hash function in use.
See link:#_hot_rod_hash_functions[Hot Rod hash functions] for details.
| Hash space size                              | vInt                     |
Modulus used by Infinispan for for all module arithmetic related to hash
code generation. Clients will likely require this information in order to
apply the correct hash calculation to the keys.
| Num servers in topology                      | vInt                     |
Number of Infinispan Hot Rod servers running within the cluster.
This could be a subset of the entire cluster if only a fraction of those
nodes are running Hot Rod servers.
| m1: Host/IP length                           | vInt                     |
Length of hostname or IP address of individual cluster member that Hot Rod
client can use to access it. Using variable length here allows for covering
for hostnames, IPv4 and IPv6 addresses.
| m1: Host/IP address                          | string                   |
String containing hostname or IP address of individual cluster member
that Hot Rod client can use to access it.
| m1: Port                                     | 2 bytes (Unsigned Short) |
Port that Hot Rod clients can use to communicat with this cluster member.
| m1: Hashcode                                 | 4 bytes                  |
32 bit integer representing the hashcode of a cluster member that a Hot Rod
client can use indentify in which cluster member a key is located having
applied the CSA to it.
| m2: Host/IP length                           | vInt                     |
| m2: Host/IP address                          | string                   |
| m2: Port                                     | 2 bytes (Unsigned Short) |
| m2: Hashcode                                 | 4 bytes                  |
| ...etc||
|==============================================================================

It's important to note that since hash headers rely on the consistent hash
algorithm used by the server and this is a factor of the cache interacted with,
hash-distribution-aware headers can only be returned to operations that target
a particular cache. Currently ping command does not target any cache
(this is to change as per link:$$https://jira.jboss.org/jira/browse/ISPN-424$$[ISPN-424])
, hence calls to ping command with hash-topology-aware client settings will
return a hash-distribution-aware header with "Num Key Owners",
"Hash Function Version", "Hash space size" and each individual host's hash
code all set to 0. This type of header will also be returned as response to
operations with hash-topology-aware client settings that are targeting caches
that are not configured with distribution.


====== Operations

.Get (0x03)/Remove (0x0B)/ContainsKey (0x0F)/GetWithVersion (0x11)

Common request format:

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Request header
| Key Length          | vInt       | Length of key. Note that the size of a
vint can be up to 5 bytes which in theory can produce bigger numbers than
Integer.MAX_VALUE. However, Java cannot create a single array that’s bigger
than Integer.MAX_VALUE, hence the protocol is limiting vint array lengths to
Integer.MAX_VALUE.
| Key                 | byte array | Byte array containing the key whose value is being requested.
|==============================================================================

Get response (0x04):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Response header
| Response status     | 1 byte     |
+0x00+ = success, if key retrieved +
+0x02+ = if key does not exist +
| Value Length        | vInt       | If success, length of value
| Value               | byte array | If success, the requested value
|==============================================================================

Remove response (0x0C):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name             | Size       | Value

| Header                 | variable   | Response header
| Response status        | 1 byte     |
+0x00+ = success, if key removed +
+0x02+ = if key does not exist +
| Previous value Length  | vInt       | If force return previous value flag was
sent in the request and the key was removed, the length of the previous value
will be returned. If the key does not exist, value length would be 0.
If no flag was sent, no value length would be present.
| Previous value         | byte array | If force return previous value flag was
sent in the request and the key was removed, previous value.
|==============================================================================

ContainsKey response (0x10):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Response header
| Response status     | 1 byte     |
+0x00+ = success, if key exists +
+0x02+ = if key does not exist +
|==============================================================================

GetWithVersion response (0x12):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Response header
| Response status     | 1 byte     |
+0x00+ = success, if key retrieved +
+0x02+ = if key does not exist +
| Entry Version       | 8 bytes    | Unique value of an existing entry's modification.
The protocol does not mandate that entry_version values are sequential.
They just need to be unique per update at the key level.
| Value Length        | vInt       | If success, length of value
| Value               | byte array | If success, the requested value
|==============================================================================

.BulkGet

Request (0x19):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Request header
| Entry count         | vInt       | Maximum number of Infinispan entries to
be returned by the server (entry == key + associated value).
Needed to support CacheLoader.load(int). If 0 then all entries are returned
(needed for CacheLoader.loadAll()).
|==============================================================================

Response (0x20):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Response header
| Response status     | 1 byte     |
+0x00+ = success, data follows +
| More                | 1 byte     | One byte representing whether more
entries need to be read from the stream. So, when it's set to 1, it means
that an entry follows, whereas when it's set to 0, it's the end of stream and
no more entries are left to read. For more information on BulkGet look
link:$$http://community.jboss.org/docs/DOC-15592$$[here]
| Key 1 Length        | vInt       | Length of key
| Key 1               | byte array | Retrieved key
| Value 1 Length      | vInt       | Length of value
| Value 1             | byte array | Retrieved value
| More                | 1 byte     |
| Key 2 Length        | vInt       |
| Key 2               | byte array |
| Value 2 Length      | vInt       |
| Value 2             | byte array |
|... etc||
|==============================================================================


.Put (0x01)/PutIfAbsent (0x05)/Replace (0x07)

Common request format:

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Request header
| Key Length          | vInt       | Length of key. Note that the size of a
vint can be up to 5 bytes which in theory can produce bigger numbers than
Integer.MAX_VALUE. However, Java cannot create a single array that’s bigger
than Integer.MAX_VALUE, hence the protocol is limiting vint array lengths to
Integer.MAX_VALUE.
| Key                 | byte array | Byte array containing the key whose value is being requested.
| Lifespan            | vInt       | Number of seconds that a entry during
which the entry is allowed to life. If number of seconds is bigger than 30 days,
this number of seconds is treated as UNIX time and so, represents the number
of seconds since 1/1/1970. If set to 0, lifespan is unlimited.
| Max Idle            | vInt       | Number of seconds that a entry can be
idle before it's evicted from the cache. If 0, no max idle time.
| Value Length        | vInt       | Length of value
| Value               | byte-array | Value to be stored
|==============================================================================

Put response (0x02):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name             | Size       | Value

| Header                 | variable   | Response header
| Response status        | 1 byte     |
+0x00+ = success, if stored +
| Previous value Length  | vInt       | If force return previous value flag was
sent in the request and the key was put, the length of the previous value
will be returned. If the key does not exist, value length would be 0.
If no flag was sent, no value length would be present.
| Previous value         | byte array | If force return previous value flag was
sent in the request and the key was put, previous value.
|==============================================================================

Replace response (0x08):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name             | Size       | Value

| Header                 | variable   | Response header
| Response status        | 1 byte     |
+0x00+ = success, if stored +
+0x01+ = if store did not happen because key does not exist +
| Previous value Length  | vInt       | If force return previous value flag was
sent in the request, the length of the previous value will be returned.
If the key does not exist, value length would be 0.
If no flag was sent, no value length would be present.
| Previous value         | byte array | If force return previous value flag was
sent in the request and the key was replaced, previous value.
|==============================================================================

PutIfAbsent response (0x06):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Response header
| Response status     | 1 byte     |
+0x00+ = success, if stored +
+0x01+ = if store did not happen because key was present +
| Previous value Length  | vInt       | If force return previous value flag was
sent in the request, the length of the previous value will be returned.
If the key does not exist, value length would be 0.
If no flag was sent, no value length would be present.
| Previous value         | byte array | If force return previous value flag was
sent in the request and the key was replaced, previous value.
|==============================================================================

.ReplaceIfUnmodified

Request (0x09):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Request header
| Key Length          | vInt       | Length of key. Note that the size of a
vint can be up to 5 bytes which in theory can produce bigger numbers than
Integer.MAX_VALUE. However, Java cannot create a single array that’s bigger
than Integer.MAX_VALUE, hence the protocol is limiting vint array lengths to
Integer.MAX_VALUE.
| Key                 | byte array | Byte array containing the key whose value is being requested.
| Lifespan            | vInt       | Number of seconds that a entry during
which the entry is allowed to life. If number of seconds is bigger than 30 days,
this number of seconds is treated as UNIX time and so, represents the number
of seconds since 1/1/1970. If set to 0, lifespan is unlimited.
| Max Idle            | vInt       | Number of seconds that a entry can be
idle before it's evicted from the cache. If 0, no max idle time.
| Entry Version       | 8 bytes    | Use the value returned by GetWithVersion operation.
| Value Length        | vInt       | Length of value
| Value               | byte-array | Value to be stored
|==============================================================================

Response (0x0A):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Response header
| Response status     | 1 byte     |
+0x00+ = success, if replaced +
+0x01+ = if replace did not happen because key had been modified +
+0x02+ = if not replaced because if key does not exist
| Previous value Length  | vInt       | If force return previous value flag was
sent in the request, the length of the previous value will be returned.
If the key does not exist, value length would be 0.
If no flag was sent, no value length would be present.
| Previous value         | byte array | If force return previous value flag was
sent in the request and the key was replaced, previous value.
|==============================================================================

.RemoveIfUnmodified

Request (0x0D):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Request header
| Key Length          | vInt       | Length of key. Note that the size of a
vint can be up to 5 bytes which in theory can produce bigger numbers than
Integer.MAX_VALUE. However, Java cannot create a single array that’s bigger
than Integer.MAX_VALUE, hence the protocol is limiting vint array lengths to
Integer.MAX_VALUE.
| Key                 | byte array | Byte array containing the key whose value is being requested.
| Entry Version       | 8 bytes    | Use the value returned by GetWithMetadata operation.
|==============================================================================

Response (0x0E):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Response header
| Response status     | 1 byte     |
+0x00+ = success, if removed +
+0x01+ = if remove did not happen because key had been modified +
+0x02+ = if not removed because key does not exist +
| Previous value Length  | vInt       | If force return previous value flag was
sent in the request, the length of the previous value will be returned.
If the key does not exist, value length would be 0.
If no flag was sent, no value length would be present.
| Previous value         | byte array | If force return previous value flag was
sent in the request and the key was removed, previous value.
|==============================================================================


.Clear

Request (0x13):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Request header
|==============================================================================

Response (0x14):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Response header
| Response status     | 1 byte     |
+0x00+ = success, if cleared +
|==============================================================================

.PutAll

Bulk operation to put all key value entries into the cache at the same time.

Request (0x2D):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Request header
| Lifespan            | vInt       | Number of seconds that provided entries
are allowed to live. If number of seconds is bigger than 30 days,
this number of seconds is treated as UNIX time and so, represents the number
of seconds since 1/1/1970. If set to 0, lifespan is unlimited.
| Max Idle            | vInt       | Number of seconds that each entry can be
idle before it's evicted from the cache. If 0, no max idle time.
| Entry count         | vInt       | How many entries are being inserted
| Key 1 Length        | vInt       | Length of key
| Key 1               | byte array | Retrieved key
| Value 1 Length      | vInt       | Length of value
| Value 1             | byte array | Retrieved value
| Key 2 Length        | vInt       |
| Key 2               | byte array |
| Value 2 Length      | vInt       |
| Value 2             | byte array |
|... continues until entry count is reached||

|==============================================================================

Response (0x2E):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Response header
| Response status     | 1 byte     |
+0x00+ = success, if all put +
|==============================================================================

.GetAll

Bulk operation to get all entries that map to a given set of keys.

Request (0x2F):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Request header
| Key count           | vInt       | How many keys to find entries for
| Key 1 Length        | vInt       | Length of key
| Key 1               | byte array | Retrieved key
| Key 2 Length        | vInt       |
| Key 2               | byte array |
|... continues until key count is reached||

|==============================================================================

Response (0x30):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Response header
| Response status     | 1 byte     |
| Entry count         | vInt       | How many entries are being returned
| Key 1 Length        | vInt       | Length of key
| Key 1               | byte array | Retrieved key
| Value 1 Length      | vInt       | Length of value
| Value 1             | byte array | Retrieved value
| Key 2 Length        | vInt       |
| Key 2               | byte array |
| Value 2 Length      | vInt       |
| Value 2             | byte array |
|... continues until entry count is reached ||
+0x00+ = success, if the get returned sucessfully +
|==============================================================================


.Stats

Returns a summary of all available statistics. For each statistic returned,
a name and a value is returned both in String UTF-8 format.
The supported stats are the following:

[options="header"]
|===============
|Name|Explanation
| timeSinceStart |Number of seconds since Hot Rod started.
| currentNumberOfEntries |Number of entries currently in the Hot Rod server.
| totalNumberOfEntries |Number of entries stored in Hot Rod server.
| stores |Number of put operations.
| retrievals |Number of get operations.
| hits |Number of get hits.
| misses |Number of get misses.
| removeHits |Number of removal hits.
| removeMisses |Number of removal misses.
|===============

Request (0x15):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Request header
|==============================================================================


Response (0x16):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Response header
| Response status     | 1 byte     |
+0x00+ = success, if stats retrieved +
| Number of stats     | vInt       | Number of individual stats returned.
| Name 1 length       | vInt       | Length of named statistic.
| Name 1              | string     | String containing statistic name.
| Value 1 length      | vInt       | Length of value field.
| Value 1             | string     | String containing statistic value.
| Name 2 length       | vInt       |
| Name 2              | string     |
| Value 2 length      | vInt       |
| Value 2             | String     |
| ...etc||
|==============================================================================

.Ping

Application level request to see if the server is available.

Request (0x17):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Request header
|==============================================================================

Response (0x18):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Response header
| Response status     | 1 byte     |
+0x00+ = success, if no errors +
|==============================================================================

.Error Handling

Error response (0x50)

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name            | Size       | Value

| Header                | variable   | Response header
| Response status       | 1 byte     |
+0x8x+ = error response code +
| Error Message Length  | vInt       | Length of error message
| Error Message         | string     | Error message. In the case of 0x84 ,
this error field contains the latest version supported by the hot rod server.
Length is defined by total body length.
|==============================================================================

.Multi-Get Operations
A multi-get operation is a form of get operation that instead of requesting a
single key, requests a set of keys. The Hot Rod protocol does not include such
operation but remote Hot Rod clients could easily implement this type of
operations by either parallelizing/pipelining individual get requests.
Another possibility would be for remote clients to use async or non-blocking
get requests. For example, if a client wants N keys, it could send send N
async get requests and then wait for all the replies. Finally, multi-get is
not to be confused with bulk-get operations. In bulk-gets, either all or a
number of keys are retrieved, but the client does not know which keys to
retrieve, whereas in multi-get, the client defines which keys to retrieve.

====== Example - Put request

* Coded request

[options="header"]
|===============
|Byte|0|1|2|3|4|5|6|7
|8| 0xA0 | 0x09 | 0x41 | 0x01 | 0x07 | 0x4D ('M') | 0x79 ('y') | 0x43 ('C')
|16| 0x61 ('a') | 0x63 ('c') | 0x68 ('h') | 0x65 ('e') | 0x00 | 0x03 | 0x00 | 0x00
|24| 0x00 | 0x05 | 0x48 ('H') | 0x65 ('e') | 0x6C ('l') | 0x6C ('l') | 0x6F ('o') | 0x00
|32| 0x00 | 0x05 | 0x57 ('W') | 0x6F ('o') | 0x72 ('r') | 0x6C ('l') | 0x64 ('d') | 

|===============

* Field explanation

[options="header"]
|===============
|Field Name|Value|Field Name|Value
|Magic (0)| 0xA0 |Message Id (1)| 0x09
|Version (2)| 0x41 |Opcode (3)| 0x01
|Cache name length (4)| 0x07 |Cache name(5-11)| 'MyCache'
|Flag (12)| 0x00 |Client Intelligence (13)| 0x03
|Topology Id (14)| 0x00 |Transaction Type (15)| 0x00
|Transaction Id (16)| 0x00 |Key field length (17)| 0x05
|Key (18 - 22)| 'Hello' |Lifespan (23)| 0x00
|Max idle (24)| 0x00 |Value field length (25)| 0x05
|Value (26-30)| 'World' ||

|===============



* Coded response

[options="header"]
|===============
|Byte|0|1|2|3|4|5|6|7
|8| 0xA1 | 0x09 | 0x01 | 0x00 | 0x00 | | | 

|===============



* Field Explanation

[options="header"]
|===============
|Field Name|Value|Field Name|Value
|Magic (0)| 0xA1 |Message Id (1)| 0x09
|Opcode (2)| 0x01 |Status (3)| 0x00
|Topology change marker (4)| 0x00 | |

|===============

===== Hot Rod Protocol 1.1

.Infinispan versions
TIP: This version of the protocol is implemented since Infinispan 5.1.0.FINAL

====== Request Header
The `version` field in the header is updated to `11`.

===== Distribution-Aware Client Topology Change Header

.Updated for 1.1
IMPORTANT: This section has been modified to be more efficient when talking
to distributed caches with virtual nodes enabled.

This is what hash-distribution-aware clients receive as response header when
a topology change is sent back:

[cols="3,^2,10",options="header"]
|==============================================================================
|Field Name                                    | Size                     | Value

| Response header with topology change marker  | variable                 |
See previous section.
| Topology Id                                  | vInt                     |
Topology ID
| Num Key Owners                               | 2 bytes (Unsigned Short) |
Globally configured number of copies for each Infinispan distributed key
| Hash Function Version                        | 1 byte                   |
Hash function version, pointing to a specific hash function in use.
See link:#_hot_rod_hash_functions[Hot Rod hash functions] for details.
| Hash space size                              | vInt                     |
Modulus used by Infinispan for for all module arithmetic related to hash
code generation. Clients will likely require this information in order to
apply the correct hash calculation to the keys.
| Num servers in topology                      | vInt                     |
Number of Infinispan Hot Rod servers running within the cluster.
This could be a subset of the entire cluster if only a fraction of those
nodes are running Hot Rod servers.
| Num Virtual Nodes Owners                     | vInt                     |
Field added in version +1.1+ of the protocol that represents the number of
configured virtual nodes. If no virtual nodes are configured or the cache
is not configured with distribution, this field will contain 0.
| m1: Host/IP length                           | vInt                     |
Length of hostname or IP address of individual cluster member that Hot Rod
client can use to access it. Using variable length here allows for covering
for hostnames, IPv4 and IPv6 addresses.
| m1: Host/IP address                          | string                   |
String containing hostname or IP address of individual cluster member
that Hot Rod client can use to access it.
| m1: Port                                     | 2 bytes (Unsigned Short) |
Port that Hot Rod clients can use to communicat with this cluster member.
| m1: Hashcode                                 | 4 bytes                  |
32 bit integer representing the hashcode of a cluster member that a Hot Rod
client can use indentify in which cluster member a key is located having
applied the CSA to it.
| m2: Host/IP length                           | vInt                     |
| m2: Host/IP address                          | string                   |
| m2: Port                                     | 2 bytes (Unsigned Short) |
| m2: Hashcode                                 | 4 bytes                  |
| ...etc||
|==============================================================================

===== Server node hash code calculation

Adding support for virtual nodes has made version +1.0+ of the Hot Rod protocol
impractical due to bandwidth it would have taken to return hash codes for all
virtual nodes in the clusters (this number could easily be in the millions).
So, as of version +1.1+ of the Hot Rod protocol, clients are given the base
hash id or hash code of each server, and then they have to calculate the real
hash position of each server both with and without virtual nodes configured.
Here are the rules clients should follow when trying to calculate a node's
hash code:

$$1.$$  With _virtual nodes disabled_ : Once clients have received the base
hash code of the server, they need to normalize it in order to find the exact
position of the hash wheel. The process of normalization involves passing the
base hash code to the hash function, and then do a small calculation to avoid
negative values. The resulting number is the node's position in the hash wheel:

[source,java]
----
public static int getNormalizedHash(int nodeBaseHashCode, Hash hashFct) {
   return hashFct.hash(nodeBaseHashCode) & Integer.MAX_VALUE; // make sure no negative numbers are involved.
}
----

$$2.$$  With _virtual nodes enabled_ : In this case, each node represents N
different virtual nodes, and to calculate each virtual node's hash code, we
need to take the the range of numbers between 0 and N-1 and apply the
following logic:

* For virtual node with 0 as id, use the technique used to retrieve a node's
hash code, as shown in the previous section.

* For virtual nodes from 1 to N-1 ids, execute the following logic:

[source,java]
----
public static int virtualNodeHashCode(int nodeBaseHashCode, int id, Hash hashFct) {
   int virtualNodeBaseHashCode = id;
   virtualNodeBaseHashCode = 31 * virtualNodeBaseHashCode + nodeBaseHashCode;
   return getNormalizedHash(virtualNodeBaseHashCode, hashFct);
}
----


===== Hot Rod Protocol 1.2

.Infinispan versions
TIP: This version of the protocol is implemented since Infinispan 5.2.0.Final. Since Infinispan 5.3.0, HotRod supports encryption via SSL. However, since this only affects the transport, the version number of the protocol has not been incremented.

====== Request Header
The `version` field in the header is updated to `12`.

Two new request operation codes have been added:

* +0x1B+ = getWithMetadata request
* +0x1D+ = bulkKeysGet request

Two new flags have been added too:

* +0x0002+	= use cache-level configured default lifespan
* +0x0004+	= use cache-level configured default max idle

====== Response Header

Two new response operation codes have been added:

* +0x1C+ = getWithMetadata response
* +0x1E+ = bulkKeysGet response

====== Operations

.GetWithMetadata

Request (0x1B):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Request header
| Key Length          | vInt       | Length of key. Note that the size of a
vint can be up to 5 bytes which in theory can produce bigger numbers than
Integer.MAX_VALUE. However, Java cannot create a single array that’s bigger
than Integer.MAX_VALUE, hence the protocol is limiting vint array lengths to
Integer.MAX_VALUE.
| Key                 | byte array | Byte array containing the key whose value is being requested.
|==============================================================================

Response (0x1C):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Response header
| Response status     | 1 byte     |
+0x00+ = success, if key retrieved +
+0x02+ = if key does not exist +
| Flag                | 1 byte     | A flag indicating whether the response
contains expiration information. The value of the flag is obtained as a
bitwise OR operation between +INFINITE_LIFESPAN (0x01)+ and
`INFINITE_MAXIDLE (0x02)`.
| Created             | Long       | (optional) a Long representing the
timestamp when the entry was created on the server. This value is returned
only if the flag's +INFINITE_LIFESPAN+ bit is not set.
| Lifespan            | vInt       | (optional) a vInt representing the
lifespan of the entry in seconds. This value is returned only if the flag's
+INFINITE_LIFESPAN+ bit is not set.
| LastUsed            | Long       | (optional) a Long representing the
timestamp when the entry was last accessed on the server. This value is
returned only if the flag's `INFINITE_MAXIDLE` bit is not set.
| MaxIdle             | vInt       | (optional) a vInt representing the
maxIdle of the entry in seconds. This value is returned only if the flag's
`INFINITE_MAXIDLE` bit is not set.
| Entry Version       | 8 bytes    | Unique value of an existing entry's modification.
The protocol does not mandate that entry_version values are sequential.
They just need to be unique per update at the key level.
| Value Length        | vInt       | If success, length of value
| Value               | byte array | If success, the requested value
|==============================================================================

.BulkKeysGet

Request (0x1D):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Request header
| Scope               | vInt       |
+0+ = Default Scope - This scope is used by RemoteCache.keySet() method.
If the remote cache is a distributed cache, the server launch a stream
operation to retrieve all keys from all of the nodes. (Remember, a
topology-aware Hot Rod Client could be load balancing the request to any
one node in the cluster). Otherwise, it'll get keys from the cache instance
local to the server receiving the request (that is because the keys should
be the same across all nodes in a replicated cache). +
+1+ = Global Scope - This scope behaves the same to Default Scope. +
+2+ = Local Scope - In case when remote cache is a distributed cache,
the server will not launch a stream operation to retrieve keys from
all nodes. Instead, it'll only get keys local from the cache instance local
to the server receiving the request. +
|==============================================================================

Response (0x1E):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Response header
| Response status     | 1 byte     |
+0x00+ = success, data follows +
| More                | 1 byte     | One byte representing whether more
keys need to be read from the stream. So, when it's set to 1, it means
that an entry follows, whereas when it's set to 0, it's the end of stream and
no more entries are left to read. For more information on BulkGet look
link:$$http://community.jboss.org/docs/DOC-15592$$[here]
| Key 1 Length        | vInt       | Length of key
| Key 1               | byte array | Retrieved key
| More                | 1 byte     |
| Key 2 Length        | vInt       |
| Key 2               | byte array |
|... etc||
|==============================================================================

===== Hot Rod Protocol 1.3

.Infinispan versions
TIP: This version of the protocol is implemented since Infinispan 6.0.0.Final.

====== Request Header
The `version` field in the header is updated to `13`.

A new request operation code has been added:

* +0x1F+ = query request

====== Response Header

A new response operation code has been added:

* +0x20+ = query response

====== Operations

.Query

Request (0x1F):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Request header
| Query Length | vInt | The length of the protobuf encoded query object
| Query | byte array | Byte array containing the protobuf encoded query object, having a length specified by previous field.
|==============================================================================

Response (0x20):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Response header
| Response payload Length | vInt | The length of the protobuf encoded response object
| Response payload | byte array | Byte array containing the protobuf encoded response object, having a length specified by previous field.
|==============================================================================

As of Infinispan 6.0, the query and response objects are specified by the protobuf message types 'org.infinispan.client.hotrod.impl.query.QueryRequest' and 'org.infinispan.client.hotrod.impl.query.QueryResponse'
defined in link:$$https://github.com/infinispan/infinispan/blob/master/remote-query/remote-query-client/src/main/resources/org/infinispan/query/remote/client/query.proto$$[remote-query/remote-query-client/src/main/resources/org/infinispan/query/remote/client/query.proto].
These definitions could change in future Infinispan versions, but as long as these evolutions will be kept backward
compatible (according to the rules defined link:$$https://developers.google.com/protocol-buffers/docs/proto#updating$$[here]) no new Hot Rod
protocol version will be introduced to accommodate this.

===== Hot Rod Protocol 2.0

.Infinispan versions
TIP: This version of the protocol is implemented since Infinispan 7.0.0.Final.

====== Request Header

The request header no longer contains `Transaction Type` and `Transaction ID`
elements since they're not in use, and even if they were in use, there are
several operations for which they would not make sense, such as `ping` or
`stats` commands. Once transactions are implemented, the protocol version will
be upped, with the necessary changes in the request header.

The `version` field in the header is updated to `20`.

Two new flags have been added:

* +0x0008+  = operation skips loading from configured cache loader.
* +0x0010+  = operation skips indexing. Only relevant when the query module is enabled for the cache

The following new request operation codes have been added:

* +0x21+ = auth mech list request
* +0x23+ = auth request
* +0x25+ = add client remote event listener request
* +0x27+ = remove client remote event listener request
* +0x29+ = size request

====== Response Header

The following new response operation codes have been added:

* +0x22+ = auth mech list response
* +0x24+ = auth mech response
* +0x26+ = add client remote event listener response
* +0x28+ = remove client remote event listener response
* +0x2A+ = size response

Two new error codes have also been added to enable clients more intelligent
decisions, particularly when it comes to fail-over logic:

* +0x87+ = Node suspected. When a client receives this error as response,
it means that the node that responded had an issue sending an operation to a
third node, which was suspected. Generally, requests that return this error
should be failed-over to other nodes.
* +0x88+ = Illegal lifecycle state. When a client receives this error as response,
it means that the server-side cache or cache manager are not available
for requests because either stopped, they're stopping or similar situation.
Generally, requests that return this error should be failed-over to other nodes.

Some adjustments have been made to the responses for the following commands in
order to better handle response decoding without the need to keep track of the
information sent. More precisely, the way previous values are parsed has changed
so that the status of the command response provides clues on whether the previous
value follows or not. More precisely:

* Put response returns `0x03` status code when put was successful
and previous value follows.
* PutIfAbsent response returns `0x04` status code only when the putIfAbsent
operation failed because the key was present and its value follows in the
response. If the putIfAbsent worked, there would have not been a previous value,
and hence it does not make sense returning anything extra.
* Replace response returns `0x03` status code only when replace happened and the
previous or replaced value follows in the response. If the replace did not happen,
it means that the cache entry was not present, and hence there's no previous value
that can be returned.
* ReplaceIfUnmodified returns `0x03` status code only when replace happened and
the previous or replaced value follows in the response.
* ReplaceIfUnmodified returns `0x04` status code only when replace did not happen
as a result of the key being modified, and the modified value follows in the response.
* Remove returns `0x03` status code when the remove happened and the previous or
removed value follows in the response. If the remove did not occur as a result
of the key not being present, it does not make sense sending any previous value
information.
* RemoveIfUnmodified returns `0x03` status code only when remove happened and
the previous or replaced value follows in the response.
* RemoveIfUnmodified returns `0x04` status code only when remove did not happen
as a result of the key being modified, and the modified value follows in the response.

===== Distribution-Aware Client Topology Change Header

In Infinispan 5.2, virtual nodes based consistent hashing was abandoned and
instead segment based consistent hash was implemented. In order to satisfy
the ability for Hot Rod clients to find data as reliably as possible,
Infinispan has been transforming the segment based consistent hash to fit
Hot Rod 1.x protocol.  Starting with version 2.0, a brand new
distribution-aware topology change header has been implemented which suppors
 segment based consistent hashing suitably and provides 100% data location
 guarantees.

[cols="3,^2,10",options="header"]
|==============================================================================
|Field Name                                    | Size                     | Value
| Response header with topology change marker  | variable                 |
| Topology Id                                  | vInt                     | Topology ID
| Num servers in topology                      | vInt                     |
Number of Infinispan Hot Rod servers running within the cluster.
This could be a subset of the entire cluster if only a fraction of those
nodes are running Hot Rod servers.
| m1: Host/IP length                           | vInt                     |
Length of hostname or IP address of individual cluster member that Hot Rod
client can use to access it. Using variable length here allows for covering
for hostnames, IPv4 and IPv6 addresses.
| m1: Host/IP address                          | string                   |
String containing hostname or IP address of individual cluster member
that Hot Rod client can use to access it.
| m1: Port                                     | 2 bytes (Unsigned Short) |
Port that Hot Rod clients can use to communicat with this cluster member.
| m2: Host/IP length                           | vInt                     |
| m2: Host/IP address                          | string                   |
| m2: Port                                     | 2 bytes (Unsigned Short) |
| ...                                          | ...                      |
| Hash Function Version                        | 1 byte                   |
Hash function version, pointing to a specific hash function in use.
See link:#_hot_rod_hash_functions[Hot Rod hash functions] for details.
| Num segments in topology                     | vInt                     |
Total number of segments in the topology
| Number of owners in segment                  | 1 byte                   |
This can be either 0, 1 or 2 owners.
| First owner's index                          | vInt                     |
Given the list of all nodes, the position of this owner in this list.
This is only present if number of owners for this segment is 1 or 2.
| Second owner's index                          | vInt                     |
Given the list of all nodes, the position of this owner in this list.
This is only present if number of owners for this segment is 2.
|==============================================================================

Given this information, Hot Rod clients should be able to recalculate all
the hash segments and be able to find out which nodes are owners for each
segment. Even though there could be more than 2 owners per segment, Hot Rod
protocol limits the number of owners to send for efficiency reasons.

====== Operations

.Auth Mech List

Request (0x21):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Request header
|==============================================================================

Response (0x22):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Response header
| Mech count | vInt | The number of mechs
| Mech 1 | string | String containing the name of the SASL mech in its IANA-registered form (e.g. GSSAPI, CRAM-MD5, etc)
| Mech 2 | string |
| ...etc |        |
|==============================================================================

The purpose of this operation is to obtain the list of valid SASL authentication mechs supported by the server. The client
will then need to issue an Authenticate request with the preferred mech.

.Authenticate

Request (0x23):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Request header
| Mech   | string   | String containing the name of the mech chosen by the client for authentication. Empty on the successive invocations
| Response length | vInt | Length of the SASL client response
| Response data   | byte array | The SASL client response
|==============================================================================

Response (0x24):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Response header
| Completed | byte | 0 if further processing is needed, 1 if authentication is complete
| Challenge length | vInt | Length of the SASL server challenge
| Challenge data   | byte array | The SASL server challenge
|==============================================================================

The purpose of this operation is to authenticate a client against a server using SASL. The authentication process, depending
on the chosen mech, might be a multi-step operation. Once complete the connection becomes authenticated

.Add client listener for remote events

Request (0x25):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Request header
| Listener ID   | byte array   | Listener identifier
| Include state | byte         | When this byte is set to `1`, cached state is
sent back to remote clients when either adding a cache listener for the first
time, or when the node where a remote listener is registered changes in a clustered
environment. When enabled, state is sent back as cache entry created events to
the clients. If set to `0`, no state is sent back to the client when adding a listener,
nor it gets state when the node where the listener is registered changes.
| Key/value filter factory name | string | Optional name of the key/value filter
factory to be used with this listener. The factory is used to create key/value
filter instances which allow events to be filtered directly in the Hot Rod
server, avoiding sending events that the client is not interested in. If no
factory is to be used, the length of the string is `0`.
| Key/value filter factory parameter count | byte | The key/value filter
factory, when creating a filter instance, can take an arbitrary number of
parameters, enabling the factory to be used to create different filter
instances dynamically. This count field indicates how many parameters will be
passed to the factory. If no factory name was provided, this field is not
present in the request.
| Key/value filter factory parameter 1 | byte array | First key/value filter
factory parameter
| Key/value filter factory parameter 2 | byte array | Second key/value filter
factory parameter
| ... | |
| Converter factory name | string | Optional name of the converter
factory to be used with this listener. The factory is used to transform the
contents of the events sent to clients. By default, when no converter is in use,
events are well defined, according to the type of event generated. However,
there might be situations where users want to add extra information to the event,
or they want to reduce the size of the events. In these cases, a converter can
be used to transform the event contents. The given converter factory name
produces converter instances to do this job. If no factory is to be used, the
length of the string is `0`.
| Converter factory parameter count | byte | The converter
factory, when creating a converter instance, can take an arbitrary number of
parameters, enabling the factory to be used to create different converter
instances dynamically. This count field indicates how many parameters will be
passed to the factory. If no factory name was provided, this field is not
present in the request.
| Converter factory parameter 1 | byte array | First converter factory parameter
| Converter factory parameter 2 | byte array | Second converter factory parameter
| ... | |
|==============================================================================

Response (0x26):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Response header
|==============================================================================

.Remove client listener for remote events

Request (0x27):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Request header
| Listener ID   | byte array   | Listener identifier
|==============================================================================

Response (0x28):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Response header
|==============================================================================

.Size

Request (0x29):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Request header
|==============================================================================

Response (0x2A):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Response header
| Size | vInt | Size of the remote cache, which is calculated globally in the
clustered set ups, and if present, takes cache store contents into account as
well.
|==============================================================================

.Exec

Request (0x2B):
[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Request header
| Script | string | Name of the task to execute
| Parameter Count | vInt | The number of parameters
| Parameter 1 Name | string | The name of the first parameter
| Parameter 1 Length | vInt | The length of the first parameter
| Parameter 1 Value | byte array | The value of the first parameter
| ...
|==============================================================================

Response (0x2C):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Response header
| Response status     | 1 byte     |
+0x00+ = success, if execution completed successfully +
+0x85+ = server error +
| Value Length        | vInt       | If success, length of return value
| Value               | byte array | If success, the result of the execution
|==============================================================================


====== Remote Events

Starting with Hot Rod 2.0, clients can register listeners for remote events
happening in the server. Sending these events commences the moment a client
adds a client listener for remote events.

Event Header:
[cols="3,^2,10",options="header"]
|==============================================================================
|Field Name           | Size       | Value

| Magic                  | 1 byte     | +0xA1+ = response
| Message ID             | vLong      | ID of event
| Opcode                 | 1 byte     | Event type: +
+0x60+ = cache entry created event +
+0x61+ = cache entry modified event +
+0x62+ = cache entry removed event +
+0x66+ = counter event +
+0x50+ = error +
| Status                 | 1 byte     | Status of the response, possible values: +
+0x00+ = No error +
| Topology Change Marker | 1 byte     | Since events are not associated with a
particular incoming topology ID to be able to decide whether a new topology is
required to be sent or not, new topologies will never be sent with events. Hence,
this marker will always have `0` value for events.
|==============================================================================

.Cache entry created event
[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Event header with `0x60` operation code
| Listener ID | byte array | Listener for which this event is directed
| Custom marker | byte | Custom event marker. For created events, this is `0`.
| Command retried | byte | Marker for events that are result of retried commands.
If command is retried, it returns `1`, otherwise `0`.
| Key | byte array | Created key
| Version | long | Version of the created entry. This version information can
be used to make conditional operations on this cache entry.
|==============================================================================

.Cache entry modified event
[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Event header with `0x61` operation code
| Listener ID | byte array | Listener for which this event is directed
| Custom marker | byte | Custom event marker. For created events, this is `0`.
| Command retried | byte | Marker for events that are result of retried commands.
If command is retried, it returns `1`, otherwise `0`.
| Key | byte array | Modified key
| Version | long | Version of the modified entry. This version information can
be used to make conditional operations on this cache entry.
|==============================================================================

.Cache entry removed event
[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Event header with `0x62` operation code
| Listener ID | byte array | Listener for which this event is directed
| Custom marker | byte | Custom event marker. For created events, this is `0`.
| Command retried | byte | Marker for events that are result of retried commands.
If command is retried, it returns `1`, otherwise `0`.
| Key | byte array | Removed key
|==============================================================================

.Custom event
[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Event header with event specific operation code
| Listener ID | byte array | Listener for which this event is directed
| Custom marker | byte | Custom event marker. For custom  events, this is `1`.
| Event data | byte array | Custom event data, formatted according to the
converter implementation logic.
|==============================================================================

===== Hot Rod Protocol 2.1

.Infinispan versions
TIP: This version of the protocol is implemented since Infinispan 7.1.0.Final.

====== Request Header

The `version` field in the header is updated to `21`.

====== Operations

.Add client listener for remote events

An extra byte parameter is added at the end which indicates whether the client
prefers client listener to work with raw binary data for filter/converter
callbacks. If using raw data, its value is `1` otherwise `0`.

Request format:

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Request header
| Listener ID   | byte array   | ...
| Include state | byte         | ...
| Key/value filter factory parameter count | byte | ...
| ... | |
| Converter factory name | string | ...
| Converter factory parameter count | byte | ...
| ... | |
| Use raw data | byte | If filter/converter parameters should be raw binary,
then `1`, otherwise `0`.
|==============================================================================

.Custom event

Starting with Hot Rod 2.1, custom events can return raw data that the Hot Rod
client should not try to unmarshall before passing it on to the user. The way
this is transmitted to the Hot Rod client is by sending `2` as the custom
event marker. So, the format of the custom event remains like this:

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Event header with event specific operation code
| Listener ID | byte array | Listener for which this event is directed
| Custom marker | byte | Custom event marker. For custom events whose event
data needs to be unmarshalled before returning to user the value is `1`. For
custom events that need to return the event data as-is to the user, the value
is `2`.
| Event data | byte array | Custom event data. If the custom marker is `1`,
the bytes represent the marshalled version of the instance returned by the
converter. If custom marker is `2`, it represents the byte array, as returned
by the converter.
|==============================================================================

===== Hot Rod Protocol 2.2

.Infinispan versions
TIP: This version of the protocol is implemented since Infinispan 8.0


Added support for different time units.

====== Operations

.Put/PutAll/PutIfAbsent/Replace/ReplaceIfUnmodified

Common request format:

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| TimeUnits           | Byte        | Time units of lifespan (first 4 bits) and maxIdle (last 4 bits). Special units
DEFAULT and INFINITE can be used for default server expiration and no expiration respectively. Possible values: +
+0x00+ = SECONDS +
+0x01+ = MILLISECONDS +
+0x02+ = NANOSECONDS +
+0x03+ = MICROSECONDS +
+0x04+ = MINUTES +
+0x05+ = HOURS +
+0x06+ = DAYS +
+0x07+ = DEFAULT +
+0x08+ = INFINITE +
| Lifespan            | vLong       | Duration which the entry is allowed to life. Only sent when time unit is not DEFAULT or INFINITE
| Max Idle            | vLong       | Duration that each entry can be idle before it's evicted from the cache. Only sent when time unit is not DEFAULT or INFINITE
|==============================================================================

===== Hot Rod Protocol 2.3

.Infinispan versions
TIP: This version of the protocol is implemented since Infinispan 8.0

====== Operations

.Iteration Start

Request (0x31):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Segments size       | signed vInt|  Size of the bitset encoding of the segments ids to iterate on. The size is the maximum segment id rounded to nearest multiple of 8. +
A value -1 indicates no segment filtering is to be done
| Segments            | byte array | (Optional) Contains the segments ids bitset encoded, where each bit with value 1 represents a segment in the set. Byte order is little-endian. +
Example: segments [1,3,12,13] would result in the following encoding: +
00001010 00110000 +
size: 16 bits +
first byte: represents segments from 0 to 7, from which 1 and 3 are set +
second byte: represents segments from 8 to 15, from which 12 and 13 are set +
More details in the java.util.BitSet implementation. Segments will be sent if the previous field is not negative
| FilterConverter size| signed vInt | The size of the String representing a KeyValueFilterConverter factory name deployed on the server, or -1 if no filter will be used
| FilterConverter     | UTF-8 byte array | (Optional) KeyValueFilterConverter factory name deployed on the server. Present if previous field is not negative
| BatchSize           | vInt        | number of entries to transfers from the server at one go
|==============================================================================

Response (0x32):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| IterationId         | String     | The unique id of the iteration
|==============================================================================


.Iteration Next

Request (0x33):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| IterationId         | String     | The unique id of the iteration
|==============================================================================

Response (0x34):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name               | Size       | Value
| Finished segments size   | vInt       | size of the bitset representing segments that were finished iterating
| Finished segments        | byte array | bitset encoding of the segments that were finished iterating
| Entry count              | vInt       | How many entries are being returned
| Key 1 Length             | vInt       | Length of key
| Key 1                    | byte array | Retrieved key
| Value 1 Length           | vInt       | Length of value
| Value 1                  | byte array | Retrieved value
| Key 2 Length             | vInt       |
| Key 2                    | byte array |
| Value 2 Length           | vInt       |
| Value 2                  | byte array |
|... continues until entry count is reached ||
|==============================================================================

.Iteration End

Request (0x35):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| IterationId         | String     | The unique id of the iteration
|==============================================================================

Response (0x36):

[cols="3,^2,10",options="header"]
|==============================================================================
| Header              | variable   | Response header
| Response status     | 1 byte     |
+0x00+ = success, if execution completed successfully +
+0x05+ = for non existent IterationId  +
|==============================================================================

===== Hot Rod Protocol 2.4

.Infinispan versions
TIP: This version of the protocol is implemented since Infinispan 8.1

This Hot Rod protocol version adds three new status code that gives the client
hints on whether the server has compatibility mode enabled or not:

* `0x06`: Success status and compatibility mode is enabled.
* `0x07`: Success status and return previous value, with compatibility mode is enabled.
* `0x08`: Not executed and return previous value, with compatibility mode is enabled.

The Iteration Start operation can optionally send parameters if a custom filter is provided and
it's parametrised:

====== Operations

.Iteration Start

Request (0x31):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size             | Value
| Segments size       | signed vInt      | same as protocol version 2.3.
| Segments            | byte array       | same as protocol version 2.3.
| FilterConverter size| signed vInt      | same as protocol version 2.3.
| FilterConverter     | UTF-8 byte array | same as protocol version 2.3.
| Parameters size     | byte             | the number of params of the filter. Only present when FilterConverter is provided.
| Parameters          | byte[][]         | an array of parameters, each parameter is a byte array. Only present if Parameters size is greater than 0.
| BatchSize           | vInt             | same as protocol version 2.3.
|==============================================================================

The Iteration Next operation can optionally return projections in the value,
meaning more than one value is contained in the same entry.

.Iteration Next

Response (0x34):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name                    | Size       | Value
| Finished segments size        | vInt       | same as protocol version 2.3.
| Finished segments             | byte array | same as protocol version 2.3.
| Entry count                   | vInt       | same as protocol version 2.3.
| Number of value projections   | vInt       | Number of projections for the values. If 1, behaves like version protocol version 2.3.
| Key1 Length                   | vInt       | same as protocol version 2.3.
| Key1                          | byte array | same as protocol version 2.3.
| Value1 projection1 length     | vInt       | length of value1 first projection
| Value1 projection1            | byte array | retrieved value1 first projection
| Value1 projection2 length     | vInt       | length of value2 second projection
| Value1 projection2            | byte array | retrieved value2 second projection
|... continues until all projections for the value retrieved
| Key2 Length                   | vInt       | same as protocol version 2.3.
| Key2                          | byte array | same as protocol version 2.3.
| Value2 projection1 length     | vInt       | length of value 2 first projection
| Value2 projection1            | byte array | retrieved value 2 first projection
| Value2 projection2 length     | vInt       | length of value 2 second projection
| Value2 projection2            | byte array | retrieved value 2 second projection
|... continues until entry count is reached ||
|==============================================================================

. Stats:

Statistics returned by previous Hot Rod protocol versions were local to the node
where the Hot Rod operation had been called. Starting with 2.4, new statistics
have been added which provide global counts for the statistics returned
previously. If the Hot Rod is running in local mode, these statistics are not
returned:

[options="header"]
|===============
|Name|Explanation
| globalCurrentNumberOfEntries |Number of entries currently across the Hot Rod cluster.
| globalStores |Total number of put operations across the Hot Rod cluster.
| globalRetrievals |Total number of get operations across the Hot Rod cluster.
| globalHits |Total number of get hits across the Hot Rod cluster.
| globalMisses |Total number of get misses across the Hot Rod cluster.
| globalRemoveHits |Total number of removal hits across the Hot Rod cluster.
| globalRemoveMisses |Total number of removal misses across the Hot Rod cluster.
|===============

===== Hot Rod Protocol 2.5

.Infinispan versions
TIP: This version of the protocol is implemented since Infinispan 8.2

This Hot Rod protocol version adds support for metadata retrieval along with entries in the iterator.
It includes two changes:

* Iteration Start request includes an optional flag
* IterationNext operation may include metadata info for each entry if the flag above is set

.Iteration Start

Request (0x31):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size             | Value
| Segments size       | signed vInt      | same as protocol version 2.4.
| Segments            | byte array       | same as protocol version 2.4.
| FilterConverter size| signed vInt      | same as protocol version 2.4.
| FilterConverter     | UTF-8 byte array | same as protocol version 2.4.
| Parameters size     | byte             | same as protocol version 2.4.
| Parameters          | byte[][]         | same as protocol version 2.4.
| BatchSize           | vInt             | same as protocol version 2.4.
| Metadata            | 1 byte           | 1 if metadata is to be returned for each entry, 0 otherwise
|==============================================================================


.Iteration Next

Response (0x34):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name               | Size       | Value
| Finished segments size   | vInt       | same as protocol version 2.4.
| Finished segments        | byte array | same as protocol version 2.4.
| Entry count              | vInt       | same as protocol version 2.4.
| Number of value projections   | vInt       | same as protocol version 2.4.
| Metadata  (entry 1)      | 1 byte     | If set, entry has metadata associated
| Expiration (entry 1)              | 1 byte     | A flag indicating whether the response
contains expiration information. The value of the flag is obtained as a
bitwise OR operation between +INFINITE_LIFESPAN (0x01)+ and
`INFINITE_MAXIDLE (0x02)`. Only present if the metadata flag above is set
| Created (entry 1)           | Long       | (optional) a Long representing the
timestamp when the entry was created on the server. This value is returned
only if the flag's +INFINITE_LIFESPAN+ bit is not set.
| Lifespan (entry 1)          | vInt       | (optional) a vInt representing the
lifespan of the entry in seconds. This value is returned only if the flag's
+INFINITE_LIFESPAN+ bit is not set.
| LastUsed (entry 1)          | Long       | (optional) a Long representing the
timestamp when the entry was last accessed on the server. This value is
returned only if the flag's `INFINITE_MAXIDLE` bit is not set.
| MaxIdle (entry 1)            | vInt       | (optional) a vInt representing the
maxIdle of the entry in seconds. This value is returned only if the flag's
`INFINITE_MAXIDLE` bit is not set.
| Entry Version (entry 1)     | 8 bytes    | Unique value of an existing entry's modification. Only present if Metadata flag is set
| Key 1 Length             | vInt       | same as protocol version 2.4.
| Key 1                    | byte array | same as protocol version 2.4.
| Value 1 Length           | vInt       | same as protocol version 2.4.
| Value 1                  | byte array | same as protocol version 2.4.
| Metadata (entry 2)              | 1 byte     | Same as for entry 1
| Expiration (entry 2)             | 1 byte     | Same as for entry 1
| Created (entry 2)           | Long      | Same as for entry 1
| Lifespan (entry 2)          | vInt      | Same as for entry 1
| LastUsed (entry 2)          | Long      | Same as for entry 1
| MaxIdle (entry 2)           | vInt      | Same as for entry 1
| Entry Version (entry 2)     | 8 bytes   | Same as for entry 1
| Key 2 Length             | vInt       |
| Key 2                    | byte array |
| Value 2 Length           | vInt       |
| Value 2                  | byte array |
|... continues until entry count is reached ||
|==============================================================================

===== Hot Rod Protocol 2.6

.Infinispan versions
TIP: This version of the protocol is implemented since Infinispan 9.0

This Hot Rod protocol version adds support for streaming get and put operations.
It includes two new operations:

* GetStream for retrieving data as a stream, with an optional initial offset
* PutStream for writing data as a stream, optionally by specifying a version

.GetStream

Request (0x37):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Request header
| Offset              | vInt       | The offset in bytes from which to start retrieving. Set to 0 to retrieve from the
beginning
| Key Length          | vInt       | Length of key. Note that the size of a
vint can be up to 5 bytes which in theory can produce bigger numbers than
Integer.MAX_VALUE. However, Java cannot create a single array that’s bigger
than Integer.MAX_VALUE, hence the protocol is limiting vint array lengths to
Integer.MAX_VALUE.
| Key                 | byte array | Byte array containing the key whose value is being requested.
|==============================================================================

.GetStream

Response (0x38):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Response header
| Response status     | 1 byte     |
+0x00+ = success, if key retrieved +
+0x02+ = if key does not exist +
| Flag                | 1 byte     | A flag indicating whether the response
contains expiration information. The value of the flag is obtained as a
bitwise OR operation between +INFINITE_LIFESPAN (0x01)+ and
`INFINITE_MAXIDLE (0x02)`.
| Created             | Long       | (optional) a Long representing the
timestamp when the entry was created on the server. This value is returned
only if the flag's +INFINITE_LIFESPAN+ bit is not set.
| Lifespan            | vInt       | (optional) a vInt representing the
lifespan of the entry in seconds. This value is returned only if the flag's
+INFINITE_LIFESPAN+ bit is not set.
| LastUsed            | Long       | (optional) a Long representing the
timestamp when the entry was last accessed on the server. This value is
returned only if the flag's `INFINITE_MAXIDLE` bit is not set.
| MaxIdle             | vInt       | (optional) a vInt representing the
maxIdle of the entry in seconds. This value is returned only if the flag's
`INFINITE_MAXIDLE` bit is not set.
| Entry Version       | 8 bytes    | Unique value of an existing entry's modification.
The protocol does not mandate that entry_version values are sequential.
They just need to be unique per update at the key level.
| Value Length        | vInt       | If success, length of value
| Value               | byte array | If success, the requested value
|==============================================================================

.PutStream

Request (0x39)
[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value

| Header              | variable   | Request header
| Entry Version       | 8 bytes    | Possible values +
0 = Unconditional put +
-1 = Put If Absent +
Other values =  pass a version obtained by `GetWithMetadata` operation to perform a conditional replace.
| Key Length          | vInt       | Length of key. Note that the size of a
vint can be up to 5 bytes which in theory can produce bigger numbers than
Integer.MAX_VALUE. However, Java cannot create a single array that’s bigger
than Integer.MAX_VALUE, hence the protocol is limiting vint array lengths to
Integer.MAX_VALUE.
| Key                 | byte array | Byte array containing the key whose value is being requested.
| Value Chunk 1 Length| vInt       | The size of the first chunk of data. If this value is 0 it means the client has
 completed transferring the value and the operation should be performed.
| Value Chunk 1       | byte array | Array of bytes forming the fist chunk of data.
| ...continues until the value is complete ||
|==============================================================================

Response (0x3A):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Response header
|==============================================================================

On top of these additions, this Hot Rod protocol version improves remote listener registration by adding a byte that indicates at a global level, which type of events the client is interested in.
For example, a client can indicate that only created events, or only expiration and removal events...etc.
More fine grained event interests, e.g. per key, can be defined using the key/value filter parameter.

So, the new add listener request looks like this:

.Add client listener for remote events

Request (0x25):

[cols="3,^2,10",options="header"]
|==============================================================================
| Field Name          | Size       | Value
| Header | variable | Request header
| Listener ID   | byte array   | Listener identifier
| Include state | byte         | When this byte is set to `1`, cached state is
sent back to remote clients when either adding a cache listener for the first
time, or when the node where a remote listener is registered changes in a clustered
environment. When enabled, state is sent back as cache entry created events to
the clients. If set to `0`, no state is sent back to the client when adding a listener,
nor it gets state when the node where the listener is registered changes.
| Key/value filter factory name | string | Optional name of the key/value filter
factory to be used with this listener. The factory is used to create key/value
filter instances which allow events to be filtered directly in the Hot Rod
server, avoiding sending events that the client is not interested in. If no
factory is to be used, the length of the string is `0`.
| Key/value filter factory parameter count | byte | The key/value filter
factory, when creating a filter instance, can take an arbitrary number of
parameters, enabling the factory to be used to create different filter
instances dynamically. This count field indicates how many parameters will be
passed to the factory. If no factory name was provided, this field is not
present in the request.
| Key/value filter factory parameter 1 | byte array | First key/value filter
factory parameter
| Key/value filter factory parameter 2 | byte array | Second key/value filter
factory parameter
| ... | |
| Converter factory name | string | Optional name of the converter
factory to be used with this listener. The factory is used to transform the
contents of the events sent to clients. By default, when no converter is in use,
events are well defined, according to the type of event generated. However,
there might be situations where users want to add extra information to the event,
or they want to reduce the size of the events. In these cases, a converter can
be used to transform the event contents. The given converter factory name
produces converter instances to do this job. If no factory is to be used, the
length of the string is `0`.
| Converter factory parameter count | byte | The converter
factory, when creating a converter instance, can take an arbitrary number of
parameters, enabling the factory to be used to create different converter
instances dynamically. This count field indicates how many parameters will be
passed to the factory. If no factory name was provided, this field is not
present in the request.
| Converter factory parameter 1 | byte array | First converter factory parameter
| Converter factory parameter 2 | byte array | Second converter factory parameter
| ... | |
| Listener even type interests  | vInt       |  A variable length number representing listener event type interests.
Each event type is represented by a bit.
Each flags is represented by a bit.
Note that since this field is sent as variable length, the most significant bit in a byte is used to determine whether more bytes need to be read, hence this bit does not represent any flag.
Using this model allows for flags to be combined in a short space.
Here are the current values for each flag: +
+0x01+ = cache entry created events
+0x02+ = cache entry modified events
+0x04+ = cache entry removed events
+0x08+ = cache entry expired events
|==============================================================================

===== Hot Rod Protocol 2.7

.Infinispan versions
TIP: This version of the protocol is implemented since JDG 7.2

This Hot Rod protocol version adds support for counter operations.

[#counter-config-encode]
.Counter Configuration encoding format

The `CounterConfiguration` class encoding format is the following:

NOTE: In counter related operation, the `Cache Name` field in Request Header can be empty.


NOTE: Summary of `Status` value in the Response Header: +
* `0x00`: Operation successful. +
* `0x01`: Operation failed. +
* `0x02`: The counter isn't defined. +
* `0x04`: The counter reached a boundary. Only possible for `STRONG` counters.

[cols="3,^2,10",options="header"]
|===
|Field Name |Size |Value

|Flags
|byte
|The `CounterType` and `Storage` encoded. Only the less significant bits are used as following: +
1st bit: `1` for `WEAK` counter and `0` for `STRONG` counter. +
2nd bit: `1` for `BOUNDED` counter and `0` for `UNBOUNDED` counter +
3rd bit: `1` for `PERSISTENT` storage and `0` for `VOLATILE` storage.

|Concurrency Level
|vInt
|(Optional) the counter's concurrency-level.
Only present if the counter is `WEAK`.

|Lower bound
|long
|(Optional) the lower bound of a bounded counter.
Only present if the counter is `BOUNDED`.

|Upper bound
|long
|(Optional) the upper bound of a bounded counter.
Only present if the counter is `BOUNDED`.

|Initial value
|long
|The counter's initial value.

|===

.Counter create operation

Creates a counter if it doesn't exist.

.Request (0x4B)
[cols="3,^2,10",options="header"]
|===
|Field Name |Size |Value

|Header
|variable
|Request header

|Name
|string
|The counter's name

|Counter Configuration
|variable
|The counter's configuration.
See <<counter-config-encode,CounterConfiguration encode>>.

|===

.Response (0x4C)
[cols="3,^2,10",options="header"]
|===
|Field Name |Size |Value

|Header
|variable
|Response header

|===

Response Header `Status` possible values:

* `0x00`: Operation successful.
* `0x01`: Operation failed. Counter is already defined.
* See the <<Response Header>> for error codes.

.Counter get configuration operation

Returns the counter's configuration.

.Request (0x4D)
[cols="3,^2,10",options="header"]
|===
|Field Name |Size |Value

|Header
|variable
|Request header

|Name
|string
|The counter's name.

|===

.Response (0x4E)
[cols="3,^2,10",options="header"]
|===
|Field Name |Size |Value

|Header
|variable
|Response header

|Counter Configuration
|variable
|(Optional) The counter's configuration.
Only present if `Status==0x00`.
See <<counter-config-encode,CounterConfiguration encode>>.

|===

Response Header `Status` possible values:

* `0x00`: Operation successful.
* `0x02`: Counter doesn't exist.
* See the <<Response Header>> for error codes.

.Counter is defined operation

Checks if the counter is defined.

.Request (0x4F)
[cols="3,^2,10",options="header"]
|===
|Field Name |Size |Value

|Header
|variable
|Request header

|Name
|string
|The counter's name

|===

.Response (0x51)
[cols="3,^2,10",options="header"]
|===
|Field Name |Size |Value

|Header
|variable
|Response header

|===

Response Header `Status` possible values:

* `0x00`: Counter is defined.
* `0x01`: Counter isn't defined.
* See the <<Response Header>> for error codes.

.Counter add-and-get operation

Adds a value to the counter and returns the new value.

.Request (0x52)
[cols="3,^2,10",options="header"]
|===
|Field Name |Size |Value

|Header
|variable
|Request header

|Name
|string
|The counter's name

|Value
|long
|The value to add

|===

.Response (0x53)
[cols="3,^2,10",options="header"]
|===
|Field Name |Size |Value

|Header
|variable
|Response header

|Value
|long
|(Optional) the counter's new value.
Only present if `Status==0x00`.

|===

NOTE: Since the `WeakCounter` doesn't have access to the new value, the `value` is zero.

Response Header `Status` possible values:

* `0x00`: Operation successful.
* `0x02`: The counter isn't defined.
* `0x04`: The counter reached its boundary. Only possible for `STRONG` counters.
* See the <<Response Header>> for error codes.

.Counter reset operation

Resets the counter's value.

.Request (0x54)
[cols="3,^2,10",options="header"]
|===
|Field Name |Size |Value

|Header
|variable
|Request header

|Name
|string
|The counter's name

|===

.Response (0x55)
[cols="3,^2,10",options="header"]
|===
|Field Name |Size |Value

|Header
|variable
|Response header

|===

Response Header `Status` possible values:

* `0x00`: Operation successful.
* `0x02`: Counter isn't defined.
* See the <<Response Header>> for error codes.

.Counter get operation

Returns the counter's value.

.Request (0x56)
[cols="3,^2,10",options="header"]
|===
|Field Name |Size |Value

|Header
|variable
|Request header

|Name
|string
|The counter's name

|===

.Response (0x57)
[cols="3,^2,10",options="header"]
|===
|Field Name |Size |Value

|Header
|variable
|Response header

|Value
|long
|(Optional) the counter's value.
Only present if `Status==0x00`.

|===

Response Header `Status` possible values:

* `0x00`: Operation successful.
* `0x02`: Counter isn't defined.
* See the <<Response Header>> for error codes.

.Counter compare-and-swap operation

Compares and only updates the counter value if the current value is the expected.

.Request (0x58)
[cols="3,^2,10",options="header"]
|===
|Field Name |Size |Value

|Header
|variable
|Request header

|Name
|string
|The counter's name

|Expect
|long
|The counter's expected value.

|Update
|long
|The counter's value to set.

|===

.Response (0x59)
[cols="3,^2,10",options="header"]
|===
|Field Name |Size |Value

|Header
|variable
|Response header

|Value
|long
|(Optional) the counter's value.
Only present if `Status==0x00`.

|===

Response Header `Status` possible values:

* `0x00`: Operation successful.
* `0x02`: The counter isn't defined.
* `0x04`: The counter reached its boundary. Only possible for `STRONG` counters.
* See the <<Response Header>> for error codes.

.Counter add and remove listener

Adds/Removes a listener for a counter

.Request ADD (0x5A) / REMOVE (0x5C)
[cols="3,^2,10",options="header"]
|===
|Field Name |Size |Value

|Header
|variable
|Request header

|Name
|string
|The counter's name

|Listener-id
|byte array
|The listener's id

|===


.Response: ADD (0x5B) / REMOVE (0x5D)
[cols="3,^2,10",options="header"]
|===
|Field Name |Size |Value

|Header
|variable
|Response header

|===


Response Header `Status` possible values:

* `0x00`: Operation successful and the connection used in the request will be used to send event (add) or the connection can be removed (remove).
* `0x01`: Operation successful and the current connection is still in use.
* `0x02`: The counter isn't defined.
* See the <<Response Header>> for error codes.

.Counter Event (0x66)

[cols="3,^2,10",options="header"]
|===
|Field Name |Size |Value

|Header
|variable
|Event header with operation code `0x66`

|Name
|string
|The counter's name

|Listener-id
|byte array
|The listener's id

|Encoded Counter State
|byte
|Encoded old and new counter state. Bit set: +
`------00`: Valid old state +
`------01`: Lower bound reached old state +
`------10`: Upper bound reached old state +
`----00--`: Valid new state +
`----01--`: Lower bound reached new state +
`----10--`: Upper bound reached new state +

|Old value
|long
|Counter's old value

|New value
|long
|Counter's new value
|===

NOTE: All counters under a `CounterManager` implementation can use the same `listener-id`.

NOTE: A connection is dedicated to a single `listener-id` and can receive events from different counters.

.Counter remove operation

Removes the counter from the cluster.

NOTE: The counter is re-created if it is accessed again.

.Request (0x5E)
[cols="3,^2,10",options="header"]
|===
|Field Name |Size |Value

|Header
|variable
|Request header

|Name
|string
|The counter's name

|===

.Response (0x5F)
[cols="3,^2,10",options="header"]
|===
|Field Name |Size |Value

|Header
|variable
|Response header

|===

Response Header `Status` possible values:

* `0x00`: Operation successful.
* `0x02`: The counter isn't defined.
* See the <<Response Header>> for error codes.

==== Hot Rod Hash Functions
Infinispan makes use of a consistent hash function to place nodes on a hash
wheel, and to place keys of entries on the same wheel to determine where
entries live.

In Infinispan 4.2 and earlier, the hash space was hardcoded to 10240, but
since 5.0, the hash space is
link:$$http://docs.oracle.com/javase/6/docs/api/java/lang/Integer.html#MAX_VALUE$$[Integer.MAX_INT] .
Please note that since Hot Rod clients should not assume a particular hash
space by default, every time a hash-topology change is detected, this value is
sent back to the client via the Hot Rod protocol.

When interacting with Infinispan via the Hot Rod protocol, it is mandated
that keys (and values) are byte arrays, to ensure platform neutral behavior.
As such, smart-clients which are aware of hash distribution on the backend
would need to be able to calculate the hash codes of such byte array keys,
again in a platform-neutral manner. To this end, the hash functions used by
Infinispan are versioned and documented, so that it can be re-implemented by
non-Java clients if needed.

The version of the hash function in use is provided in the Hot Rod protocol,
as the hash function version parameter.

.  Version 1 (single byte, 0x01) The initial version of the hash function in
use is based on
link:$$https://github.com/infinispan/infinispan/blob/master/commons/src/main/java/org/infinispan/commons/hash/MurmurHash2.java$$[Austin Appleby's MurmurHash 2.0 algorithm] , a fast, non-cryptographic hash that exhibits excellent distribution, collision resistance and avalanche behavior.  The specific version of the algorithm used is the slightly slower, endian-neutral version that allows consistent behavior across both big- and little-endian CPU architectures.  Infinispan's version also hard-codes the hash seed as -1. For details of the algorithm, please visit link:$$http://sites.google.com/site/murmurhash/$$[Austin Appleby's MurmurHash 2.0 page].
Other implementations are detailed on
link:$$http://en.wikipedia.org/wiki/MurmurHash$$[Wikipedia] .
This hash function was the default one used by the Hot Rod server until Infinispan 4.2.1.
Since Infinispan 5.0, the server never uses hash version 1.
Since Infinispan 9.0, the client ignores hash version 1.

.  Version 2 (single byte, 0x02) Since Infinispan 5.0, a new hash function is
used by default which is based on
link:$$https://github.com/infinispan/infinispan/blob/master/commons/src/main/java/org/infinispan/commons/hash/MurmurHash3.java$$[Austin Appleby's MurmurHash 3.0 algorithm].
Detailed information about the hash function can be found in this
link:$$http://code.google.com/p/smhasher/wiki/MurmurHash3$$[wiki].
Compared to 2.0, it provides better performance and spread.
Since Infinispan 7.0, the server only uses version 2 for HotRod 1.x clients.

. Version 3 (single byte, 0x03) Since Infinispan 7.0, a new hash function is used by default.
The function is still based on
link:$$http://code.google.com/p/smhasher/wiki/MurmurHash3$$[wiki],
but is also aware of the hash segments used in the server's
link:https://github.com/infinispan/infinispan/blob/master/core/src/main/java/org/infinispan/distribution/ch/ConsistentHash.java[ConsistentHash].

==== Hot Rod Admin Tasks
Admin operations are handled by the Exec operation with a set of well known tasks. Admin tasks are named according to the following rules:

`@@context@name`

All parameters are UTF-8 encoded strings.
Parameters are specific to each task, with the exception of the *flags* parameter which is common to all commands.
The *flags* parameter contains zero or more space-separated values which may affect the behaviour of the command.
The following table lists all currently available flags.

Admin tasks return the result of the operation represented as a JSON string.

.FLAGS
[cols="3,10",options="header"]
|==============================================================================
| Flag | Description
| permanent | Requests that the command's effect be made permanent into the server's configuration. If the server cannot comply with the request, the entire operation will fail with an error
|==============================================================================

===== Admin tasks

.@@cache@create
[cols="3,10,2",options="header"]
|==============================================================================
| Parameter       | Description | Required
| name  | The name of the cache to create. | Yes
| template | The name of the cache configuration template to use for the new cache.|No
| flags | See the flags table above. |No
|==============================================================================

.@@cache@remove
[cols="3,10,2",options="header"]
|==============================================================================
| Parameter       | Description | Required
| name  | The name of the cache to remove. | Yes
| flags | See the flags table above. |No
|==============================================================================

.@@cache@names
[cols="3,10,2",options="header"]
|==============================================================================
| Parameter       | Description | Required
|==============================================================================

Returns the cache names as a JSON array of strings, e.g. ["cache1", "cache2"]

.@@cache@reindex
[cols="3,10,2",options="header"]
|==============================================================================
| Parameter       | Description | Required
| name  | The name of the cache to reindex. | Yes
| flags | See the flags table above. |No, all flags will be ignored
|==============================================================================
