Flush pending writes before closing the connection on caught exceptions#6226
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vietj
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Jul 6, 2026
vietj
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- Flush pending writes before closing the connection on caught exceptions
- Add a VertxConnectionTest reproducing the flush before close on exception
- Move the flush-before-close-on-exception regression test to NetTest
- Always close through the channel in VertxHandler.exceptionCaught
- Remove comment
- Skip the WebSocket closing handshake timeout on exception
Motivation: When an exception is caught on a connection, VertxHandler#exceptionCaught dispatches the throwable to the user handlers and then closes the channel with chctx.close(). A response written from the handler -- for instance a 400 written from request().exceptionHandler() when HttpContentDecompressor throws a DecoderException on a malformed compressed body -- is enqueued in the outbound message queue but not flushed, because VertxConnection#write skips the flush while a read is in progress. chctx.close() then causes Netty to discard the unflushed entries from the ChannelOutboundBuffer, so the response never reaches the client: the client observes a connection reset instead of the intended HTTP response. Changes: Route the exception-driven close through the channel so it traverses the pipeline tail and invokes VertxHandler#close -> VertxConnection#writeClose, which flushes pending writes (an empty buffer with forceFlush=true) and closes the channel only once the flush has completed. This is the same flush-then-close path already used by graceful shutdown, idle close and the regular close(); the exception path simply was not using it. The bare chctx.close() is kept as a fallback for the case where no connection has been set yet (handlerAdded has not run), since VertxHandler#close dereferences it. Add a regression test, Http1xTest#testRequestDecompressionInvalidBodyDeliversErrorResponse, that sends a malformed gzip body to a server with decompression enabled and asserts the client receives the response written from the request exception handler. HTTP/2 is unaffected: its codec replaces VertxHandler in the pipeline, so connection-level exceptions do not go through this path. Signed-off-by: Alexandru Salajan <alexandru17@gmail.com>
…tion Covers the fix at the connection layer: a write queued (unflushed) when a caught exception triggers the close must reach the channel before it closes, otherwise Netty's ChannelOutboundBuffer discards the unflushed entry. The test fails without the VertxHandler.exceptionCaught change and passes with it. Signed-off-by: Alexandru Salajan <alexandru17@gmail.com>
The fix is at the transport layer (VertxHandler/VertxConnection) and is not HTTP specific, so exercise it over plain TCP rather than HTTP. Drop Http1xTest#testRequestDecompressionInvalidBodyDeliversErrorResponse and add NetTest#testFlushPendingWriteOnExceptionClose, which parks an unflushed write on a NetServer connection, triggers a caught exception that closes it, and asserts the client still receives the bytes before the close. Signed-off-by: Alexandru Salajan <alexandru17@gmail.com>
A regular connection close already closes at the channel level, so the exception-driven close should too; there is no good reason to close from the channel handler context. Drop the connection != null / chctx.close() fallback and always use chctx.channel().close(). Signed-off-by: Alexandru Salajan <alexandru17@gmail.com>
Signed-off-by: Alexandru Salajan <alexandru17@gmail.com>
When an exception aborts the connection there is no point waiting for the peer's close frame, so set the closing timeout to 0 in handleException. Signed-off-by: Alexandru Salajan <alexandru17@gmail.com>
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