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fix: send the SSE response head before the first event - #1605
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No active review issues were identified for the change enabling early SSE header delivery.
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What changed in this PR
Fixes #1598 by flushing the SSE output stream before invoking the event writer, allowing clients to receive status and headers while a stream is idle, without waiting for an event or heartbeat.
Changes:
- Adds an initial flush to
EventStreamRepresentationwithout changing its API. - Adds HTTP/1.1 and HTTP/2 regression tests using the JDK client to verify headers arrive before the first event.
- Records the fix in the changelog; Restlet client body-peeking behavior remains outside this PR’s scope.
| File | Description |
|---|---|
org.restlet/src/test/java/org/restlet/engine/connector/EventStreamConnectorTestCase.java |
Tests early header delivery and subsequent event reading over both HTTP versions. |
org.restlet/src/main/java/org/restlet/representation/EventStreamRepresentation.java |
Flushes the output stream before running the event writer. |
changes.md |
Documents early SSE header delivery for issue #1598. |
Review effort: Balanced
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The Netty server connector writes the response head without flushing it, and flushes it with the first body bytes. An EventStreamRepresentation whose writer waited before its first event, without heartbeats, so sent no status or headers until then. EventStreamRepresentation.write() now flushes the output stream before running the writer. A connector test checks, with the JDK HTTP client, that the head of an idle stream arrives over HTTP/1.1 and HTTP/2. Fixes #1598. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Signed-off-by: Jerome Louvel <374450+jlouvel@users.noreply.github.com>
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Fixes #1598.
Summary
The Netty server connector writes the response head without flushing it, and flushes it with the first body bytes. So an
EventStreamRepresentationwhose writer waited before its first event, with heartbeats off, sent no status or headers until that event.EventStreamRepresentation.write()now flushes the output stream before running the writer. This commits the head at once, at the cost of one empty flush per stream, with no API change.Testing
EventStreamConnectorTestCasehas two new tests, over HTTP/1.1 and HTTP/2 (h2c upgrade). Each serves an idle stream without heartbeats and checks that the status, protocol version andContent-Typearrive within 5 seconds, before the first event. The event is then read.These tests use the JDK HTTP client, which returns a response as soon as its head arrives. Both fail without the fix (timeout) and pass with it.
EventStreamTestCaseandEventStreamConnectorTestCasepass locally (12 tests). The full core suite runs on CI.Note: the Restlet client still waits for the first byte
The Restlet HTTP client returns a response only after peeking at the first body byte (
NettyClientCall.nonEmpty). With the Restlet client,Client.handle()therefore still blocks on an idle stream, even though the head has arrived. #1556 (R0) removes that peek for HTTP/2 streams. HTTP/1.1 would need a separate change, so it isn't part of this PR.🤖 Generated with Claude Code