Ktor — SSE Logging

Experimental

SSE inspection is in early preview and under active development. APIs are marked with @ExperimentalWiretapSseApi and may change in future releases. We're looking for early feedback — please open an issue if you run into problems or have suggestions.

Setup

Install the Ktor SSE plugin and the Wiretap SSE plugin. SSE APIs require opt-in:

@OptIn(ExperimentalWiretapSseApi::class)
val client = HttpClient {
    install(SSE)
    install(WiretapKtorSsePlugin)    // SSE logging (experimental)
    install(WiretapKtorHttpPlugin)   // HTTP logging
}

Automatic Session Wrapping

WiretapKtorSsePlugin wraps SSE sessions automatically — no extra calls needed. Just use the session directly and all incoming events are logged:

@OptIn(ExperimentalWiretapSseApi::class)
client.sse("https://example.com/events") {
    incoming.collect { event ->
        println("Event: ${event.event} — ${event.data}")
    }
}

WiretapSseSession API

Property	Type	Description
call	HttpClientCall	The underlying HTTP call for this SSE connection
incoming	Flow<ServerSentEvent>	Incoming events with automatic logging

How It Works

1. WiretapKtorSsePlugin automatically wraps SSE sessions and creates a connection entry via SseLogManager with status Open
2. The wrapped LoggingSseSession intercepts the Ktor ClientSSESession
3. Every incoming event is logged as it flows through the incoming flow
4. When the flow completes (server close, cancellation, or error), the connection status is updated to Closed or Failed

What Gets Logged

Connection

• URL
• Request headers
• Status transitions (Open → Closed / Failed)
• Failure message (if applicable)
• Timestamps

Events

• Event type (event field)
• Data payload
• Event ID (id field)
• Retry interval (retry field)
• Byte count
• Timestamp

Complete Example

@OptIn(ExperimentalWiretapSseApi::class)
val client = HttpClient {
    install(SSE)
    install(WiretapKtorSsePlugin)
    install(WiretapKtorHttpPlugin)
}

@OptIn(ExperimentalWiretapSseApi::class)
client.sse("https://api.example.com/stream") {
    incoming.collect { event ->
        when (event.event) {
            "message" -> handleMessage(event.data)
            "heartbeat" -> { /* ignore */ }
            else -> println("Unknown event: ${event.event}")
        }
    }
}

All SSE events are automatically captured — they appear in the SSE tab of the inspector UI.