Restart HeartbeatProcess on transient pipe errors#391
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When the monitor subprocess exits unexpectedly (e.g. due to a transient network/Redis error), @pipe.write raises IOError or Errno::EPIPE. With abort_on_exception=true on the heartbeat thread, this killed the entire worker mid-run, causing tests to be skipped. HeartbeatProcess#tick! now catches these errors, restarts the subprocess via a new restart! method, and retries up to MAX_RESTART_ATTEMPTS (3) consecutive failures before re-raising. The counter resets on each successful tick so transient errors don't exhaust the budget permanently. Also adds mocha as a dev dependency and a dedicated test file covering retry, restart, max-attempts, and counter-reset behaviour.
thadcraft-shopify
approved these changes
Apr 8, 2026
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Previously, if the
HeartbeatProcessmonitor subprocess exited unexpectedly -- due to a transient Redis connection error, OOM killer, or OS signal -- the next@pipe.writeinsend_messagewould raiseIOError: closed streamorErrno::EPIPE. Since the heartbeat thread runs withabort_on_exception = true, this killed the worker mid-run, causing tests to be skipped and connections not returned to the pool.HeartbeatProcess#tick!now rescues those errors, restarts the subprocess via a newrestart!method, and retries. It allows up toMAX_RESTART_ATTEMPTS(3) consecutive failures before re-raising, and resets the counter on each successful tick so transient errors don't exhaust the budget permanently.Also adds mocha as a dev dependency for the new unit tests.