= RabbitMQ Streams Protocol Reference

This is the reference of the RabbitMQ Streams protocol. Note the protocol
is still under development and is subject to change.

The https://github.com/rabbitmq/rabbitmq-stream-java-client[RabbitMQ Stream Java client]
is currently the reference implementation.

== Types

int8, int16, int32, int64 - Signed integers (big endian order)

uint8, uint16, uint32, uint64 - Unsigned integers (big endian order)

bytes - int32 for the length followed by the bytes of content, length of -1 indicates null.

string - int16 for the length followed by the bytes of UTF8-encoded content, length of -1 indicates null.

arrays - int32 for the length followed by the repetition of the structure, notation uses [], e.g.
[int32] for an array of int32.

== Frame Structure

```
Frame => Size (Request | Response | Command)
  Size => uint32 (size without the 4 bytes of the size element)

Request => Key Version (CorrelationId) Content
  Key => uint16
  Version => uint16
  CorrelationId => uint32
  Command => bytes // see command details below

Response => Key Version CorrelationId ResponseCode
  Key => uint16
  Version => uint16
  CorrelationId => uint32
  ResponseCode => uint16

Command => Key Version Content
  Key => uint16
  Version => uint16
  Content => bytes // see command details below
```

Most commands are request/reply, but some commands (e.g. `Deliver`) are one-direction only and thus
does not contain a correlation ID.

Some responses may carry additional information than just the response code, this is specified in the command definition.

Keys are uint16, but the actual value is defined on the last 15 bits, the most significant bit being
used to make the difference between a request (0) and a response (1). Example for `subscribe`
(key is 6):

```
0x0006 => subscribe request
0x8006 => subscribe response
```

== Response Codes

.Stream Protocol Response Codes
|===
|Response|Code

|OK|0x01
|Stream does not exist|0x02
|Subscription ID already exists|0x03
|Subscription ID does not exist|0x04
|Stream already exists|0x05
|Stream not available|0x06
|SASL mechanism not supported|0x07
|Authentication failure|0x08
|SASL error|0x09
|SASL challenge|0x0a
|SASL authentication failure loopback|0x0b
|Virtual host access failure|0x0c
|Unknown frame|0x0d
|Frame too large|0x0e
|Internal error|0x0f
|Access refused|0x10
|Precondition failed|0x11
|Publisher does not exist|0x12
|No offset|0x13

|===

== Commands

.Stream Protocol Commands
|===
|Command |From |Key | Expects response?

|<<declarepublisher>>
|Client
|0x0001
|Yes

|<<publish>>
|Client
|0x0002
|No

|<<publishconfirm>>
|Server
|0x0003
|No

|<<publisherror>>
|Server
|0x0004
|No

|<<querypublishersequence>>
|Client
|0x0005
|Yes

|<<deletepublisher>>
|Client
|0x0006
|Yes

|<<subscribe>>
|Client
|0x0007
|Yes

|<<deliver>>
|Server
|0x0008
|No

|<<credit>>
|Client
|0x0009
|No

|<<storeoffset>>
|Client
|0x000a
|No

|<<queryoffset>>
|Client
|0x000b
|Yes

|<<unsubscribe>>
|Client
|0x000c
|Yes

|<<create>>
|Client
|0x000d
|Yes

|<<delete>>
|Client
|0x000e
|Yes

|<<metadata>>
|Client
|0x000f
|Yes

|<<metadataupdate>>
|Server
|0x0010
|No

|<<peerproperties>>
|Client
|0x0011
|Yes

|<<saslhandshake>>
|Client
|0x0012
|Yes

|<<saslauthenticate>>
|Client
|0x0013
|Yes

|<<tune>>
|Server
|0x0014
|Yes

|<<open>>
|Client
|0x0015
|Yes

|<<close>>
|Client & Server
|0x0016
|Yes

|<<heartbeat>>
|Client & Server
|0x0017
|No

|<<route>> (experimental)
|Client
|0x0018
|Yes

|<<partitions>> (experimental)
|Client
|0x0019
|Yes
|===

=== DeclarePublisher

```
DeclarePublisherRequest => Key Version CorrelationId PublisherId [PublisherReference] Stream
  Key => uint16 // 0x0001
  Version => uint16
  CorrelationId => uint32
  PublisherId => uint8
  PublisherReference => string // max 256 characters
  Stream => string

DeclarePublisherResponse => Key Version CorrelationId ResponseCode
  Key => uint16 // 0x8001
  Version => uint16
  CorrelationId => uint32
  ResponseCode => uint16
```

=== Publish

```
Publish => Key Version PublisherId PublishedMessages
  Key => uint16 // 0x0002
  Version => uint16
  PublisherId => uint8
  PublishedMessages => [PublishedMessage]
  PublishedMessage => PublishingId Message
  PublishingId => uint64
  Message => bytes
```

=== PublishConfirm

```
PublishConfirm => Key Version PublishingIds
  Key => uint16 // 0x0003
  Version => uint16
  PublisherId => uint8
  PublishingIds => [uint64] // to correlate with the messages sent
```

=== PublishError

```
PublishError => Key Version [PublishingError]
  Key => uint16 // 0x0004
  Version => uint16
  PublisherId => uint8
  PublishingError => PublishingId Code
  PublishingId => uint64
  Code => uint16 // code to identify the problem
```

=== QueryPublisherSequence

```
QueryPublisherRequest => Key Version CorrelationId PublisherReference Stream
  Key => uint16 // 0x0005
  Version => uint16
  CorrelationId => uint32
  PublisherReference => string // max 256 characters
  Stream => string

QueryPublisherResponse => Key Version CorrelationId ResponseCode Sequence
  Key => uint16 // 0x8005
  Version => uint16
  CorrelationId => uint32
  ResponseCode => uint16
  Sequence => uint64
```

=== DeletePublisher

```
DeletePublisherRequest => Key Version CorrelationId PublisherId
  Key => uint16 // 0x0006
  Version => uint16
  CorrelationId => uint32
  PublisherId => uint8

DeletePublisherResponse => Key Version CorrelationId ResponseCode
  Key => uint16 // 0x8006
  Version => uint16
  CorrelationId => uint32
  ResponseCode => uint16
```

=== Subscribe

```
Subscribe => Key Version CorrelationId SubscriptionId Stream OffsetSpecification Credit Properties
  Key => uint16 // 0x0007
  Version => uint16
  CorrelationId => uint32 // correlation id to correlate the response
  SubscriptionId => uint8 // client-supplied id to identify the subscription
  Stream => string // the name of the stream
  OffsetSpecification => OffsetType Offset
  OffsetType => uint16 // 1 (first), 2 (last), 3 (next), 4 (offset), 5 (timestamp)
  Offset => uint64 (for offset) | int64 (for timestamp)
  Credit => uint16
  Properties => [Property]
  Property => Key Value
  Key => string
  Value => string
```

NB: Timestamp is https://www.erlang.org/doc/apps/erts/time_correction.html#Erlang_System_Time[Erlang system time],
milliseconds from epoch

=== Deliver

```
Deliver => Key Version SubscriptionId OsirisChunk
  Key => uint16 // 0x0008
  Version => uint16
  SubscriptionId => uint8
  OsirisChunk => MagicVersion NumEntries NumRecords Epoch ChunkFirstOffset ChunkCrc DataLength Messages
  MagicVersion => int8
  ChunkType => int8 // 0: user, 1: tracking delta, 2: tracking snapshot
  NumEntries => uint16
  NumRecords => uint32
  Timestamp => int64 // erlang system time in milliseconds, since epoch
  Epoch => uint64
  ChunkFirstOffset => uint64
  ChunkCrc => int32
  DataLength => uint32
  TrailerLength => uint32
  Reserved => unit32 // unused 4 bytes
  Messages => [Message] // no int32 for the size for this array; the size is defined by NumEntries field above
  Message => EntryTypeAndSize
  Data => bytes
```

NB: See the https://github.com/rabbitmq/osiris/blob/f32df7563a036b1687c0208a3cb5f9e8f5cee937/src/osiris_log.erl#L101[Osiris project]
for details on the structure of messages.

=== Credit

```
Credit => Key Version SubscriptionId Credit
  Key => uint16 // 0x0009
  Version => uint16
  SubscriptionId => uint8
  Credit => uint16 // the number of chunks that can be sent

CreditResponse => Key Version ResponseCode SubscriptionId
  Key => uint16 // 0x8009
  Version => uint16
  ResponseCode => uint16
  SubscriptionId => uint8
```

NB: the server sent a response only in case of problem, e.g. crediting an unknown subscription.

=== StoreOffset

```
StoreOffset => Key Version Reference Stream Offset
  Key => uint16 // 0x000a
  Version => uint16
  Reference => string // max 256 characters
  Stream => string // the name of the stream
  Offset => uint64
```

=== QueryOffset

```
QueryOffsetRequest => Key Version CorrelationId Reference Stream
  Key => uint16 // 0x000b
  Version => uint16
  CorrelationId => uint32
  Reference => string // max 256 characters
  Stream => string

QueryOffsetResponse => Key Version CorrelationId ResponseCode Offset
  Key => uint16 // 0x800b
  Version => uint16
  CorrelationId => uint32
  ResponseCode => uint16
  Offset => uint64
```

=== Unsubscribe

```
Unsubscribe => Key Version CorrelationId SubscriptionId
  Key => uint16 // 0x000c
  Version => uint16
  CorrelationId => uint32
  SubscriptionId => uint8
```

=== Create

```
Create => Key Version CorrelationId Stream Arguments
  Key => uint16 // 0x000d
  Version => uint16
  CorrelationId => uint32
  Stream => string
  Arguments => [Argument]
  Argument => Key Value
  Key => string
  Value => string
```

=== Delete

```
Delete => Key Version CorrelationId Stream
  Key => uint16 // 0x000e
  Version => uint16
  CorrelationId => uint32
  Stream => string
```

=== Metadata

```
MetadataQuery => Key Version CorrelationId [Stream]
  Key => uint16 // 0x000f
  Version => uint16
  CorrelationId => uint32
  Stream => string

MetadataResponse => Key Version CorrelationId [Broker] [StreamMetadata]
  Key => uint16 // 0x800f
  Version => uint16
  CorrelationId => uint32
  Broker => Reference Host Port
    Reference => uint16
    Host => string
    Port => uint32
  StreamMetadata => StreamName ResponseCode LeaderReference ReplicasReferences
     StreamName => string
     ResponseCode => uint16
     LeaderReference => uint16
     ReplicasReferences => [uint16]
```

=== MetadataUpdate

```
MetadataUpdate => Key Version MetadataInfo
  Key => uint16 // 0x0010
  Version => uint16
  MetadataInfo => Code Stream
  Code => uint16 // code to identify the information
  Stream => string // the stream implied
```

=== PeerProperties

```
PeerPropertiesRequest => Key Version PeerProperties
  Key => uint16 // 0x0011
  Version => uint16
  CorrelationId => uint32
  PeerProperties => [PeerProperty]
  PeerProperty => Key Value
  Key => string
  Value => string

PeerPropertiesResponse => Key Version CorrelationId ResponseCode PeerProperties
  Key => uint16 // 0x8011
  Version => uint16
  CorrelationId => uint32
  ResponseCode => uint16
  PeerProperties => [PeerProperty]
  PeerProperty => Key Value
  Key => string
  Value => string
```

=== SaslHandshake

```
SaslHandshakeRequest => Key Version CorrelationId Mechanism
  Key => uint16 // 0x0012
  Version => uint16
  CorrelationId => uint32
  Mechanism => string

SaslHandshakeResponse => Key Version CorrelationId ResponseCode [Mechanisms]
  Key => uint16 // 0x8012
  Version => uint16
  CorrelationId => uint32
  ResponseCode => uint16
  Mechanisms => [Mechanism]
  Mechanism => string
```

=== SaslAuthenticate

```
SaslAuthenticateRequest => Key Version CorrelationId Mechanism SaslOpaqueData
  Key => uint16 // 0x0013
  Version => uint16
  CorrelationId => uint32
  Mechanism => string
  SaslOpaqueData => bytes

SaslAuthenticateResponse => Key Version CorrelationId ResponseCode SaslOpaqueData
  Key => uint16 // 0x8013
  Version => uint16
  CorrelationId => uint32
  ResponseCode => uint16
  SaslOpaqueData => bytes
```

=== Tune

```
TuneRequest => Key Version FrameMax Heartbeat
  Key => uint16 // 0x0014
  Version => uint16
  FrameMax => uint32 // in bytes, 0 means no limit
  Heartbeat => uint32 // in seconds, 0 means no heartbeat

TuneResponse => TuneRequest
```

=== Open

```
OpenRequest => Key Version CorrelationId VirtualHost
  Key => uint16 // 0x0015
  Version => uint16
  CorrelationId => uint32
  VirtualHost => string

OpenResponse => Key Version CorrelationId ResponseCode ConnectionProperties
  Key => uint16 // 0x8015
  Version => uint16
  CorrelationId => uint32
  ResponseCode => uint16
  ConnectionProperties => [ConnectionProperty]
  ConnectionProperty => Key Value
  Key => string
  Value => string
```

=== Close

```
CloseRequest => Key Version CorrelationId ClosingCode ClosingReason
  Key => uint16 // 0x0016
  Version => uint16
  CorrelationId => uint32
  ClosingCode => uint16
  ClosingReason => string

CloseResponse => Key Version CorrelationId ResponseCode
  Key => uint16 // 0x8016
  Version => uint16
  CorrelationId => uint32
  ResponseCode => uint16
```

=== Heartbeat

```
Heartbeat => Key Version
  Key => uint16 // 0x0017
  Version => uint16
```

=== Route

_Experimental_

```
RouteQuery => Key Version CorrelationId RoutingKey SuperStream
  Key => uint16 // 0x0018
  Version => uint16
  CorrelationId => uint32
  RoutingKey => string
  SuperStream => string

RouteResponse => Key Version CorrelationId [Stream]
  Key => uint16 // 0x8018
  Version => uint16
  CorrelationId => uint32
  Stream => string
```

=== Partitions

_Experimental_

```
PartitionsQuery => Key Version CorrelationId SuperStream
  Key => uint16 // 0x0019
  Version => uint16
  CorrelationId => uint32
  SuperStream => string

PartitionsResponse => Key Version CorrelationId [Stream]
  Key => uint16 // 0x8019
  Version => uint16
  CorrelationId => uint32
  Stream => string
```

== Authentication

Once a client is connected to the server, it initiates an authentication
sequence. The next figure shows the steps of the sequence:

[ditaa]
.Authentication Sequence
....
Client                      Server
  +                           +
  | Peer Properties Exchange  |
  |-------------------------->|
  |<--------------------------|
  |                           |
  |      SASL Handshake       |
  |-------------------------->|
  |<--------------------------|
  |                           |
  |     SASL Authenticate     |
  |-------------------------->|
  |<--------------------------|
  |                           |
  |           Tune            |
  |<--------------------------|
  |-------------------------->|
  |                           |
  |           Open            |
  |-------------------------->|
  |<--------------------------|
  |                           |
  +                           +
....

* SaslHandshake: the client asks about the SASL mechanisms the server supports. It
can then pick one from the list the server returns.
* SaslAuthenticate: the client answers to the server's challenge(s), using the
SASL mechanism it picked. The server will send a `Tune` frame once it is satisfied
with the client authentication response.
* Tune: the server sends a `Tune` frame to suggest some settings (max frame size, heartbeat).
The client answers with a `Tune` frame with the settings he agrees on, possibly adjusted
from the server's suggestions.
* Open: the client sends an `Open` frame to pick a virtual host to connect to. The server
answers whether it accepts the access or not.

== Resources

- https://docs.google.com/presentation/d/1Hlv4qaWm2PRU04dVPmShP9wU7TEQEttXdsbV8P54Uvw/edit#slide=id.gdbeadf9676_0_37[RabbitMQ Streams client] : a general guide line to write a streams client
- https://docs.google.com/presentation/d/1BFwf01LcicZ-SyxE1CycZv2gUQMPFGdtFkVuXhgkoTE/edit#slide=id.p1[RabbitMQ Streams Internals]: how the streams work internally 
