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https://issues.apache.org/jira/browse/ZOOKEEPER-1607?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13798617#comment-13798617
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Hadoop QA commented on ZOOKEEPER-1607:
--------------------------------------
-1 overall. Here are the results of testing the latest attachment
http://issues.apache.org/jira/secure/attachment/12609061/ZOOKEEPER-1607.patch
against trunk revision 1533161.
+1 @author. The patch does not contain any @author tags.
+1 tests included. The patch appears to include 3 new or modified tests.
+1 javadoc. The javadoc tool did not generate any warning messages.
-1 javac. The patch appears to cause tar ant target to fail.
-1 findbugs. The patch appears to cause Findbugs (version 1.3.9) to fail.
+1 release audit. The applied patch does not increase the total number of
release audit warnings.
-1 core tests. The patch failed core unit tests.
+1 contrib tests. The patch passed contrib unit tests.
Test results:
https://builds.apache.org/job/PreCommit-ZOOKEEPER-Build/1705//testReport/
Console output:
https://builds.apache.org/job/PreCommit-ZOOKEEPER-Build/1705//console
This message is automatically generated.
> Read-only Observer
> ------------------
>
> Key: ZOOKEEPER-1607
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1607
> Project: ZooKeeper
> Issue Type: Improvement
> Components: server
> Affects Versions: 3.4.3
> Reporter: Thawan Kooburat
> Assignee: Raul Gutierrez Segales
> Fix For: 3.5.0
>
> Attachments: ZOOKEEPER-1607.patch
>
>
> This feature reused some of the mechanism already provided by
> ReadOnlyZooKeeper (ZOOKEEPER-704) but implemented in a different way
> Goal: read-only clients should be able to connect to the observer or continue
> to read data from the observer event when there is an outage of underling
> quorum. This means that it is possible for the observer to provide 100% read
> uptime for read-only local session (ZOOKEEPER-1147)
> Implementation:
> The observer don't tear down itself when it lose connection with the leader.
> It only close the connection associated with non read-only sessions and
> global sessions. So the client can try other observer if this is a temporal
> failure.
> During the outage, the observer switch to read-only mode. All the pending and
> future write requests get will get NOT_READONLY error. Read-only state
> transition is sent to all session on that observer. The observer only accepts
> a new connection from a read-only client.
> When the observer is able to reconnect to the leader. It sends state
> transition (CONNECTED_STATE) to all current session. If it is able to
> synchronize with the leader using DIFF, the steam of txns is sent through the
> commit processor instead of applying to the DataTree directly to prevent
> raise condition between in-flight read requests (see ZOOKEEPER-1505). The
> client will receive watch events correctly and can start issuing write
> requests.
> However, if the observer is getting the snapshot. It need to drop all the
> connection since it cannot fire a watch correctly.
>
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