fix(mongodb-runner): handle arbiter RS convergence race in metadata check - #770
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addaleax merged 4 commits intoJun 25, 2026
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…heck When a replica set is initiated, the code only waits for a PRIMARY to appear before proceeding to assertAllServersHaveInsertedLocalMetadata(). An arbiter node may still be transitioning to ARBITER state at that point, so hello.arbiterOnly can be undefined while this.isArbiter is already true, causing an immediate "Arbiter flag mismatch" throw. Fix _ensureMatchingMetadataColl to retry via eventually() when isArbiter is true but hello has not yet confirmed arbiterOnly, giving the member time to converge. Also handle the deserialize() ordering where isArbiter is set after _populateBuildInfo runs by skipping the check when hello.arbiterOnly is true regardless of the local flag. Add unit tests covering the retry path, immediate-success path, timeout propagation, and the deserialize ordering edge case.
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Coverage is 78.727% — blink1073:check-arbiter-race-condition into mongodb-js:main. No base build found for |
addaleax
approved these changes
Jun 25, 2026
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Description
Fixes an intermittent failure when starting a replica set with an arbiter. After
replSetInitiate, an arbiter node may still be transitioning toARBITERstate whenassertAllServersHaveInsertedLocalMetadata()runs, causing a spurious "Arbiter flag mismatch" error. The fix retries thehellocheck until the member converges (or a timeout is reached), and also handles an ordering edge case indeserialize().Tracked in https://jira.mongodb.org/browse/DRIVERS-3538.
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