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ASF GitHub Bot commented on ZOOKEEPER-261: ------------------------------------------ Github user hanm commented on the issue: https://github.com/apache/zookeeper/pull/120 Nit: the PR title should contain the string "ZOOKEEPER-261" for the merge script to work - otherwise comments made here will not be bridged to JIRA https://issues.apache.org/jira/browse/ZOOKEEPER-261 > Reinitialized servers should not participate in leader election > --------------------------------------------------------------- > > Key: ZOOKEEPER-261 > URL: https://issues.apache.org/jira/browse/ZOOKEEPER-261 > Project: ZooKeeper > Issue Type: Improvement > Components: leaderElection, quorum > Reporter: Benjamin Reed > > A server that has lost its data should not participate in leader election > until it has resynced with a leader. Our leader election algorithm and > NEW_LEADER commit assumes that the followers voting on a leader have not lost > any of their data. We should have a flag in the data directory saying whether > or not the data is preserved so that the the flag will be cleared if the data > is ever cleared. > Here is the problematic scenario: you have have ensemble of machines A, B, > and C. C is down. the last transaction seen by C is z. a transaction, z+1, is > committed on A and B. Now there is a power outage. B's data gets > reinitialized. when power comes back up, B and C comes up, but A does not. C > will be elected leader and transaction z+1 is lost. (note, this can happen > even if all three machines are up and C just responds quickly. in that case C > would tell A to truncate z+1 from its log.) in theory we haven't violated our > 2f+1 guarantee, since A is failed and B still hasn't recovered from failure, > but it would be nice if when we don't have quorum that system stops working > rather than works incorrectly if we lose quorum. -- This message was sent by Atlassian JIRA (v6.3.4#6332)