NRG (2.11): Fix term handling in candidate state and use higher term from vote request #5671
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…te request A candidate could incorrectly revert to an older term without resetting if an old AE arrived with a term that is at least newer than the pterm but not necessarily newer than the term. Also a node that is isolated for a period of time with a high term number should cause the rest of the cluster to move forward with that term number, rather than going backwards to the leader term. Co-authored-by: Reuben Ninan <reuben@nats.io> Signed-off-by: Neil Twigg <neil@nats.io>
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A candidate could incorrectly revert to an older term without resetting if an old AE arrived with a term that is at least newer than the pterm but not necessarily newer than the term.
Additionally, we also weren't handling the case that the rest of the cluster should assume the higher term number from the vote requests once an isolated candidate node rejoins the cluster.
This PR also rewrites
TestNRGCandidateStepsDownAfterAEand replaces it withTestNRGAssumeHighTermAfterCandidateIsolationas the old test was checking for flawed behaviour: it was relying on the term being able to go backwards after a period of isolation, which is not correct. Instead we should prove that the rest of the cluster assumes the higher term from the isolated node.Co-authored-by: Reuben Ninan reuben@nats.io
Signed-off-by: Neil Twigg neil@nats.io