Commands

Catalog

The u32 command codes. Replicated commands are identified on the wire by their operation byte (see Operation discriminants). The code column below is the protocol-level registry and, for non-replicated commands, the value carried in header bytes 196..200.

# System
PING = 1                                  # non-replicated; works without login
GET_STATS = 10                            # non-replicated
GET_SNAPSHOT = 11                         # non-replicated
GET_CLUSTER_METADATA = 12                 # non-replicated
DESCRIBE_OPTIONS = 13                     # non-replicated
GET_ME = 20                               # non-replicated
GET_CLIENT = 21                           # non-replicated
GET_CLIENTS = 22                          # non-replicated

# Users
GET_USER = 31                             # non-replicated
GET_USERS = 32                            # non-replicated
CREATE_USER = 33                          # operation 141
DELETE_USER = 34                          # operation 143
UPDATE_USER = 35                          # operation 142
UPDATE_PERMISSIONS = 36                   # operation 145
CHANGE_PASSWORD = 37                      # operation 144
LOGIN_USER = 38                           # legacy; server rejects with MalformedLogin eviction
LOGOUT_USER = 39                          # operation 3 (Logout)
LOGIN_REGISTER = 40                       # operation 1 (Register)
LOGIN_REGISTER_WITH_PAT = 45              # operation 1 (Register)

# Personal access tokens
GET_PERSONAL_ACCESS_TOKENS = 41           # non-replicated
CREATE_PERSONAL_ACCESS_TOKEN = 42         # operation 146
DELETE_PERSONAL_ACCESS_TOKEN = 43         # operation 147
LOGIN_WITH_PERSONAL_ACCESS_TOKEN = 44     # legacy; server rejects with MalformedLogin eviction

# Messages
POLL_MESSAGES = 100                       # non-replicated
SEND_MESSAGES = 101                       # operation 160
FLUSH_UNSAVED_BUFFER = 102                # parses, but always fails with FeatureUnavailable

# Consumer offsets
GET_CONSUMER_OFFSET = 120                 # non-replicated
STORE_CONSUMER_OFFSET = 121               # operation 161
DELETE_CONSUMER_OFFSET = 122              # operation 162

# Streams
GET_STREAM = 200                          # non-replicated
GET_STREAMS = 201                         # non-replicated
CREATE_STREAM = 202                       # operation 128
DELETE_STREAM = 203                       # operation 130
UPDATE_STREAM = 204                       # operation 129
PURGE_STREAM = 205                        # operation 131

# Topics
GET_TOPIC = 300                           # non-replicated
GET_TOPICS = 301                          # non-replicated
CREATE_TOPIC = 302                        # operation 132
DELETE_TOPIC = 303                        # operation 134
UPDATE_TOPIC = 304                        # operation 133
PURGE_TOPIC = 305                         # operation 135

# Partitions
CREATE_PARTITIONS = 402                   # operation 136
DELETE_PARTITIONS = 403                   # operation 137

# Segments
DELETE_SEGMENTS = 503                     # operation 138

# Consumer groups
GET_CONSUMER_GROUP = 600                  # non-replicated
GET_CONSUMER_GROUPS = 601                 # non-replicated
CREATE_CONSUMER_GROUP = 602               # operation 139
DELETE_CONSUMER_GROUP = 603               # operation 140
JOIN_CONSUMER_GROUP = 604                 # operation 148
LEAVE_CONSUMER_GROUP = 605                # operation 149
SYNC_CONSUMER_GROUP = 606                 # non-replicated

FLUSH_UNSAVED_BUFFER still decodes on the wire, but the server has no on-demand flush primitive and answers every call with FeatureUnavailable. Per-topic durability is configured with the enforce_fsync topic option instead.

Payloads

Payloads below are the request body (the bytes after the 256-byte header). Types reference the shared encodings. Empty payload means the body has zero bytes.

System

Ping. Code: 1. Empty payload. The only command accepted before login.

Get stats. Code: 10. Empty payload.

Get snapshot. Code: 11.

[compression: u8][types_count: u8][snapshot_type: u8] x types_count

Compression codes: 1 = Stored, 2 = Deflated, 3 = Bzip2, 4 = Zstd, 5 = Lzma, 6 = Xz. Snapshot type codes: 1 = FilesystemOverview, 2 = ProcessList, 3 = ResourceUsage, 4 = Test, 5 = ServerLogs, 6 = ServerConfig, 100 = All.

Get cluster metadata. Code: 12. Empty payload.

Describe options. Code: 13.

[scope: u8]

Scope: 1 = topic, 2 = stream, 3 = user. Returns the option catalog for the scope: keys, value kinds, defaults, and descriptions. See Options block.

Get me. Code: 20. Empty payload.

Get client. Code: 21.

[client_id: u32]

Get clients. Code: 22. Empty payload.

Streams

Get stream. Code: 200.

[stream_id: Identifier]

Get streams. Code: 201. Empty payload.

Create stream. Code: 202.

[name_len: u8][name: N][options block to end]

The stream option catalog is empty today, so the block is normally empty (zero bytes).

Delete stream. Code: 203.

[stream_id: Identifier]

Update stream. Code: 204.

[stream_id: Identifier][name_len: u8][name: N][options block to end]

Patch semantics: absent option keys are left unchanged.

Purge stream. Code: 205.

[stream_id: Identifier]

Topics

Get topic. Code: 300.

[stream_id: Identifier][topic_id: Identifier]

Get topics. Code: 301.

[stream_id: Identifier]

Create topic. Code: 302.

[stream_id: Identifier][partitions_count: u32][name_len: u8][name: N][options block to end]

The fixed fields are the shape of the operation: which stream, how many partitions, what name. Every topic setting (compression_algorithm, message_expiry, max_topic_size, segment_size, enforce_fsync, messages_required_to_save, size_of_messages_required_to_save, preallocate_segments) rides the options block. See Topic options. partitions_count is an argument, not a setting: it is consumed at admission and never persisted as an option.

Delete topic. Code: 303.

[stream_id: Identifier][topic_id: Identifier]

Update topic. Code: 304.

[stream_id: Identifier][topic_id: Identifier][name_len: u8][name: N][options block to end]

Only compression_algorithm, message_expiry, and max_topic_size are updatable. Absent keys are left unchanged.

Purge topic. Code: 305.

[stream_id: Identifier][topic_id: Identifier]

Partitions

Create partitions. Code: 402.

[stream_id: Identifier][topic_id: Identifier][partitions_count: u32]

Delete partitions. Code: 403.

[stream_id: Identifier][topic_id: Identifier][partitions_count: u32]

Segments

Delete segments. Code: 503.

[stream_id: Identifier][topic_id: Identifier][partition_id: u32][segments_count: u32]

Deletes the segments_count oldest sealed segments of the partition.

Messages

Poll messages. Code: 100.

[consumer: Consumer][stream_id: Identifier][topic_id: Identifier]
[partition_flag: u8][partition_id: u32]
[strategy: 9 bytes][count: u32][auto_commit: u8]

strategy is a polling strategy. count is the requested number of messages. auto_commit = 1 stores the consumer offset server-side as part of the poll.

The response body:

[partition_id: u32][current_offset: u64][messages_count: u32]
[batch records to end]

The 16-byte prefix is followed by a stream of batch records served as stored: each record's header carries the stamped base_offset and base_timestamp, and each frame's deltas resolve against them. A record may be a server-sliced view of a larger stored batch, so the first polled offset is base_offset + offset_delta of the first frame, not necessarily base_offset itself. current_offset is the partition's newest offset at poll time.

Send messages. Code: 101.

[metadata_length: u32]
[stream_id: Identifier][topic_id: Identifier][partitioning: Partitioning]
[messages_count: u32]
[batch: 256-byte batch header + frames]

metadata_length counts the bytes from stream_id through messages_count inclusive, so a reader can skip straight to the batch. The producer leaves partition_id, base_offset, and base_timestamp zero in the batch header, and the server stamps them. Every checksum is producer-computed and verified at admission. The reserved regions must be zero.

Flush unsaved buffer. Code: 102.

[stream_id: Identifier][topic_id: Identifier][partition_id: u32][fsync: u8]

Parses, but the server always answers FeatureUnavailable: there is no on-demand flush primitive. Use the per-topic enforce_fsync option for durability guarantees.

Consumer offsets

Get consumer offset. Code: 120.

[consumer: Consumer][stream_id: Identifier][topic_id: Identifier]
[partition_flag: u8][partition_id: u32]

Response body (20 bytes):

[partition_id: u32][current_offset: u64][stored_offset: u64]

Store consumer offset. Code: 121.

[consumer: Consumer][stream_id: Identifier][topic_id: Identifier]
[partition_flag: u8][partition_id: u32][offset: u64][ack: u8]

Delete consumer offset. Code: 122.

[consumer: Consumer][stream_id: Identifier][topic_id: Identifier]
[partition_flag: u8][partition_id: u32][ack: u8]

The trailing ack byte is mandatory on both write commands. A payload without it fails to decode. Ack levels:

Value	Level	Meaning
0	`NoAck`	Leader-local write; respond as soon as local state is updated (the fast path `PollMessages` auto-commit uses)
1	`Quorum`	Replicate through partition consensus; respond after a quorum commit (default for explicit writes)

Consumer groups

Get consumer group. Code: 600.

[stream_id: Identifier][topic_id: Identifier][group_id: Identifier]

Get consumer groups. Code: 601.

[stream_id: Identifier][topic_id: Identifier]

Create consumer group. Code: 602.

[stream_id: Identifier][topic_id: Identifier][name_len: u8][name: N]

Delete consumer group. Code: 603.

[stream_id: Identifier][topic_id: Identifier][group_id: Identifier]

Join consumer group. Code: 604.

[stream_id: Identifier][topic_id: Identifier][group_id: Identifier]

Leave consumer group. Code: 605.

[stream_id: Identifier][topic_id: Identifier][group_id: Identifier]

Sync consumer group. Code: 606.

[stream_id: Identifier][topic_id: Identifier][group_id: Identifier]

Read-only: a member asks for its current partition assignment and the group generation, so it can select partitions to poll client-side.

Users

Get user. Code: 31.

[user_id: Identifier]

Get users. Code: 32. Empty payload.

Create user. Code: 33.

[username_len: u8][username: N][password_len: u8][password: N][status: u8]
[has_permissions: u8][permissions_len: u32, only when has_permissions = 1][permissions: M bytes]
[options block to end]

permissions_len and the permissions bytes are present only when has_permissions = 1. When it is 0 the options block follows immediately. The user option catalog is empty today, so the block is normally empty. status: 1 = active, 2 = inactive.

Delete user. Code: 34.

[user_id: Identifier]

Update user. Code: 35.

[user_id: Identifier]
[has_username: u8][username_len: u8, only when 1][username: N, only when 1]
[has_status: u8][status: u8, only when 1]
[options block to end]

Update permissions. Code: 36.

[user_id: Identifier][has_permissions: u8]
[permissions_len: u32, only when has_permissions = 1][permissions: M bytes, only when 1]

As in CreateUser, the length field is conditional: with has_permissions = 0 the payload ends at the flag.

Change password. Code: 37.

[user_id: Identifier]
[current_password_len: u8][current_password: N]
[new_password_len: u8][new_password: N]

Authentication

Login register. Code: 40. Operation::Register. The body is ClientVersionInfo + credentials, described in Login-register.
Login register with PAT. Code: 45. Operation::Register. The body is ClientVersionInfo + token.
Logout user. Code: 39. Operation::Logout. Empty payload.
Codes 38 and 44 are the pre-register login shapes. The server rejects both with a MalformedLogin eviction.

Personal access tokens

Get personal access tokens. Code: 41. Empty payload.

Create personal access token. Code: 42.

[name_len: u8][name: N][expiry: u64]

expiry is a duration in microseconds. Two sentinel values exist: 0 (server default, which currently means no expiry) and u64::MAX (never expires).

Delete personal access token. Code: 43.

[name_len: u8][name: N]

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