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https://issues.apache.org/jira/browse/ZOOKEEPER-261?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15819905#comment-15819905
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ASF GitHub Bot commented on ZOOKEEPER-261:
------------------------------------------
Github user enixon commented on a diff in the pull request:
https://github.com/apache/zookeeper/pull/120#discussion_r95714094
--- Diff: bin/zkServer-initialize.sh ---
@@ -113,6 +113,8 @@ initialize() {
else
echo "No myid provided, be sure to specify it in $ZOO_DATADIR/myid
if using non-standalone"
fi
+
+ date > "$ZOO_DATADIR/initialize"
--- End diff --
True enough, `touch` is sufficient. Using `date` is an optimization I've
included in other scripts in the past as a way of sneaking a bit more
information into an otherwise meaningless file but in this context it's
probably just confusing.
> 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.
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