NRG: peer removing all followers leaves membership in progress#7609
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neilalexander merged 1 commit intomainfrom Dec 4, 2025
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Fix the case where a node that removes all of the peers would be left with `membChanging` set permanently. This would prevent the single node cluster to admit new nodes back to form a bigger cluster. The `membChanging` flag prevents concurrent membership changes, and is reset after a membership change is committed. However, in the case of a single node cluster, entries are never committed and `memChanging` remains set. The underlying problem is that single node clusters are not working properly: entries are committed only after tracking successful append entry responses from the followers. In a single node cluster there's no one that sends append entry responses, and the quorum checking is never done elsewhere. The fix consists in extracting function `tryCommit` from `trackResponse`. `tryCommit` checks if there's a quorum for a given index, and if so it commits the corresponding entry. We call this function if, after proposing a peer remove, we are left with a single node cluster. Signed-off-by: Daniele Sciascia <daniele@nats.io>
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Fix the case where a node that removes all of the peers would be left with
membChangingset permanently. This would prevent the single node cluster to admit new nodes back to form a bigger cluster. ThemembChangingflag prevents concurrent membership changes, and is reset after a membership change is committed. However, in the case of a single node cluster, entries are never committed andmemChangingremains set.The underlying problem is that single node clusters are not working properly: entries are committed only after tracking successful append entry responses from the followers. In a single node cluster there's no one that sends append entry responses, and the quorum checking is never done elsewhere.
The fix consists in extracting function
tryCommitfromtrackResponse.tryCommitchecks if there's a quorum for a given index, and if so it commits the corresponding entry. We call this function if, after proposing a peer remove, we are left with a single node cluster.Signed-off-by: Daniele Sciascia danele@nats.io