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https://issues.apache.org/jira/browse/ZOOKEEPER-261?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15727294#comment-15727294
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ASF GitHub Bot commented on ZOOKEEPER-261:
------------------------------------------
Github user hanm commented on a diff in the pull request:
https://github.com/apache/zookeeper/pull/120#discussion_r91208138
--- Diff:
src/java/main/org/apache/zookeeper/server/persistence/FileTxnSnapLog.java ---
@@ -165,8 +173,41 @@ public File getSnapDir() {
*/
public long restore(DataTree dt, Map<Long, Integer> sessions,
PlayBackListener listener) throws IOException {
- snapLog.deserialize(dt, sessions);
+ long deserializeResult = snapLog.deserialize(dt, sessions);
FileTxnLog txnLog = new FileTxnLog(dataDir);
+ boolean suspectEmptyDB;
+ File initFile = new File(dataDir.getParent(), "initialize");
+ if (initFile.exists()) {
+ if (!initFile.delete()) {
+ LOG.warn("Unable to delete initialization file " +
initFile.toString());
--- End diff --
It sounds pretty serious issue if the initialize file can't be cleaned up
upon startup of a new ensemble for whatever reasons as the presence of this
file is the key promise made here - not able to clean it up will possibly lead
to inconsistent quorum state again that this PR is trying to fix. So, maybe
throw an IOException here to abort server start process and let admin intervene
instead?
> 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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