# `PhoenixMicro.Transport.Kafka`
[🔗](https://github.com/iamkanishka/phoenix_micro/blob/v1.0.0/lib/phoenix_micro/transport/kafka.ex#L1)

Pure-Elixir Kafka transport for `phoenix_micro`.

Implements the Kafka binary wire protocol directly over TCP using
Erlang's `:gen_tcp`. **Zero external dependencies** — no `kafka_ex`,
no `:brod`, no `crc32cer`, no C compiler, no rebar3.

Works on every platform: Linux, macOS, Windows.

## Supported Kafka wire APIs

| API | Key | Purpose |
|---|---|---|
| Produce | 0 | Publish messages |
| Fetch | 1 | Consume messages |
| ListOffsets | 2 | Get earliest/latest offsets |
| Metadata | 3 | Topic/partition discovery |
| OffsetCommit | 8 | Commit consumer offsets |
| OffsetFetch | 9 | Fetch committed offsets |
| FindCoordinator | 10 | Consumer group coordinator |
| JoinGroup | 11 | Join consumer group |
| Heartbeat | 12 | Keep group membership alive |
| LeaveGroup | 13 | Clean group exit |
| SyncGroup | 14 | Receive partition assignment |

## Configuration

    config :phoenix_micro,
      transport: :kafka,
      transports: [
        kafka: [
          brokers: [{"localhost", 9092}],
          # OR: url: "kafka://broker1:9092,broker2:9092",
          group_id:           "my_app",
          client_id:          "phoenix_micro",
          begin_offset:       :latest,       # :latest | :earliest | integer
          acks:               1,             # 0=none 1=leader -1=all
          ack_timeout_ms:     5_000,
          max_bytes:          1_048_576,
          fetch_wait_ms:      500,
          heartbeat_ms:       3_000,
          session_timeout_ms: 30_000
        ]
      ]

## Docker Compose

    services:
      kafka:
        image: bitnami/kafka:3.7
        ports:
          - "9092:9092"
        environment:
          KAFKA_CFG_NODE_ID: "0"
          KAFKA_CFG_PROCESS_ROLES: "broker,controller"
          KAFKA_CFG_LISTENERS: "PLAINTEXT://:9092,CONTROLLER://:9093"
          KAFKA_CFG_ADVERTISED_LISTENERS: "PLAINTEXT://localhost:9092"
          KAFKA_CFG_LISTENER_SECURITY_PROTOCOL_MAP: "CONTROLLER:PLAINTEXT,PLAINTEXT:PLAINTEXT"
          KAFKA_CFG_CONTROLLER_QUORUM_VOTERS: "0@kafka:9093"
          KAFKA_CFG_CONTROLLER_LISTENER_NAMES: "CONTROLLER"

# `t`

```elixir
@type t() :: %PhoenixMicro.Transport.Kafka{
  ack_timeout_ms: term(),
  acks: term(),
  begin_offset: term(),
  brokers: term(),
  client_id: term(),
  config: term(),
  connected: term(),
  fetch_wait_ms: term(),
  group_id: term(),
  heartbeat_ms: term(),
  max_bytes: term(),
  reconnect_attempts: term(),
  session_timeout_ms: term(),
  subscriptions: term(),
  task_sup: term()
}
```

# `child_spec`

```elixir
@spec child_spec(keyword()) :: Supervisor.child_spec()
```

Returns a specification to start this module under a supervisor.

See `Supervisor`.

# `start_link`

```elixir
@spec start_link(keyword()) :: GenServer.on_start()
```

---

*Consult [api-reference.md](api-reference.md) for complete listing*