SSE Streaming

SSE Stream Flow

SSE Stream Characteristics

Feature	Behavior
Reader Tracking	Each reader gets unique `reader_id` for independent position tracking
Heartbeats	Sent every 5 seconds when no data available
Auto-Timeout	Stream closes automatically after extended inactivity
Session TTL	Default 10 minutes (600 seconds)
Event Format	Standard SSE: `data: {json}\n\n`

SSE Lifecycle Events

sse.stream.start

Sent when SSE stream connection opens.

{
  "type": "sse.stream.start",
  "event_data": {
    "session_id": "lsn-abc123",
    "reader_id": "reader_xyz"
  }
}

sse.stream.heartbeat

Sent periodically when no data events are available.

{
  "type": "sse.stream.heartbeat",
  "event_data": {
    "session_id": "lsn-abc123",
    "session_status": "SESSION_STATUS_RUNNING",
    "num_messages": 42,
    "num_bytes": 15234,
    "message_timeout": 2.5,
    "reader_id": "reader_xyz"
  }
}

sse.stream.end

Sent when stream closes (timeout or session termination).

{
  "type": "sse.stream.end",
  "event_data": {
    "session_id": "lsn-abc123",
    "session_status": "SESSION_STATUS_RUNNING",
    "num_messages": 100,
    "num_bytes": 45678,
    "message_timeout": 58.2,
    "reader_id": "reader_xyz"
  }
}

{
  "type": "sse.stream.end",
  "event_data": {
    "session_id": "lsn-abc123",
    "reader_id": "reader_xyz",
    "session_status": "SESSION_STATUS_KILLED",
    "warning": "Session status is : SESSION_STATUS_KILLED"
  }
}

SSE Reader Statistics

Each reader tracks the following metrics:

Metric	Description
`num_messages`	Total messages sent to this reader
`num_bytes`	Total bytes transmitted
`num_errors`	Transmission errors encountered
`stream_send_delay_sec`	95th percentile send latency
`sse_start_time`	Stream start timestamp
`sse_end_time`	Stream end timestamp
`sse_run_time`	Total stream duration

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SSE Stream Flow

SSE Stream Characteristics

SSE Lifecycle Events

sse.stream.start

sse.stream.heartbeat

sse.stream.end

SSE Reader Statistics

​SSE Stream Flow

​SSE Stream Characteristics

​SSE Lifecycle Events

​sse.stream.start

​sse.stream.heartbeat

​sse.stream.end

​SSE Reader Statistics

SSE Stream Flow

SSE Stream Characteristics

SSE Lifecycle Events

sse.stream.start

sse.stream.heartbeat

sse.stream.end

SSE Reader Statistics