stdin: fix watcher mode swallowing first message after reload#392
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stdin: fix watcher mode swallowing first message after reload#392
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When watcher mode reloads config, the old stdin consumer's bufio.Scanner blocks in os.Stdin.Read and cannot be cancelled. A new consumer starts a second Read on the same fd, and whichever goroutine wins the race consumes the data — if the old one wins, the message is silently dropped. Replace io.NopCloser(os.Stdin) with a singleton relay goroutine that owns the only Read on os.Stdin and fans data through a channel. Each consumer gets a cancelableStdinReader whose Read selects on the relay channel, the caller's context, and a close signal. On context cancellation the old reader returns immediately, unblocking the scanner so the goroutine can exit, and the next consumer picks up seamlessly from the same relay. Closes redpanda-data/connect#1733 Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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When watcher mode reloads config, the old stdin consumer's bufio.Scanner blocks in os.Stdin.Read and cannot be cancelled. A new consumer starts a second Read on the same fd, and whichever goroutine wins the race consumes the data — if the old one wins, the message is silently dropped.
Replace io.NopCloser(os.Stdin) with a singleton relay goroutine that owns the only Read on os.Stdin and fans data through a channel. Each consumer gets a cancelableStdinReader whose Read selects on the relay channel, the caller's context, and a close signal. On context cancellation the old reader returns immediately, unblocking the scanner so the goroutine can exit, and the next consumer picks up seamlessly from the same relay.
Closes redpanda-data/connect#1733