[v26.2.x] kafka/client: authenticate under the reconnect mutex - #31273
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nvartolomei merged 1 commit intoJul 24, 2026
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remote_broker released the reconnect mutex before authenticating, so two concurrent dispatches on a fresh SASL connection could race: the second caller saw the half-set-up connection, skipped auth, and sent its request mid-handshake, which the broker rejects by dropping the connection. Hold the mutex across both reconnect and authentication so a concurrent caller waits until the connection is fully established. On auth failure discard the transport, since SASL authenticates a connection once and recovery must reconnect. Note: the SASL round-trips are bounded by the transport's default request timeout rather than the caller's abort source, which now also caps how long the reconnect mutex is held during auth. This is deliberate: the connect/auth attempt is shared by every caller queued on the mutex, so one caller's abort must not cut short work the others are waiting on -- an aborting caller simply stops waiting on the mutex. Tests cover the race and post-failure connection reuse. (cherry picked from commit b08c929)
nvartolomei
approved these changes
Jul 24, 2026
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Backport of PR #31152