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https://issues.apache.org/jira/browse/ZOOKEEPER-261?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15727911#comment-15727911
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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_r91234951
--- Diff:
src/java/main/org/apache/zookeeper/server/persistence/FileTxnSnapLog.java ---
@@ -132,6 +137,9 @@ public FileTxnSnapLog(File dataDir, File snapDir)
throws IOException {
txnLog = new FileTxnLog(this.dataDir);
snapLog = new FileSnap(this.snapDir);
+
+ autoCreateDB =
Boolean.parseBoolean(System.getProperty(ZOOKEEPER_DB_AUTOCREATE,
--- End diff --
I included `ZOOKEEPER_DB_AUTOCREATE` to allow users to opt out of the
feature until they're ready to update their ensemble management tooling to
support creating the new file. Is that in accord with Zookeeper style?
On the question of style, `ZOOKEEPER_DB_AUTOCREATE_DEFAULT` exists purely
because `ZOOKEEPER_DATADIR_AUTOCREATE_DEFAULT` exists above it in the file. If
including the defaults as static constants isn't Zookeeper style then I'm happy
to replace it with a string literal in the constructor.
> 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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