Fix H2 window flow control bugs causing flaky CI timeouts#582
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- Use negotiated SETTINGS_INITIAL_WINDOW_SIZE for new streams instead of hardcoded 65535 (OverallWindowSize). Streams created after the SETTINGS exchange were missing the server's initial window, causing the client to block on an exhausted stream window while the server believed it had plenty — root cause of 30s timeouts on large request bodies. - Set Remote PeerSetting.WindowSize default to 65535 (RFC 9113 §6.5.2). - Fix _initDone = false (should be true) in H2ConnectionPool.Init(), which allowed double-initialization of the connection. - Fix lost-wakeup race in WindowSizeHolder: wake a waiter whenever the window is positive, not only on the ≤0 → >0 transition. Concurrent UpdateWindowSize calls could silently skip the wake. - Make StreamPool.ShouldWindowUpdate thread-safe with Interlocked ops. - Add larger payload (150002 * 16) to Http2ClientHandler test coverage.
This was referenced Mar 30, 2026
This was referenced Apr 13, 2026
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Summary
OverallWindowSize(65535) instead of the server's negotiated initial window size. When the server advertises a larger window (e.g. 1MB), the client exhausts 65535 bytes then blocks waiting for a stream-level WINDOW_UPDATE that the server never sends (it believes the stream still has plenty of window). This is the root cause of 30s timeouts on large request bodies (e.g.Check_Global_Healthwith 150KB)._initDoneguard fixed:Init()set_initDone = falseinstead oftrue, allowing double-initialization of the connection (duplicate preface + read/write loops).UpdateWindowSizecalls raced, only the one crossing the 0-to-positive boundary would wake a waiter. The other's increment was silently added without waking anyone, starving blocked streams.+=withInterlocked.AddandInterlocked.Exchange.Http2ClientHandler.GetHttpMethods.