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https://issues.apache.org/jira/browse/ZOOKEEPER-1607?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13735392#comment-13735392
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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/12597187/0001-RFC-Don-t-tear-down-an-Observer-when-we-lose-connect.patch
against trunk revision 1503101.
+1 @author. The patch does not contain any @author tags.
-1 tests included. The patch doesn't appear to include any new or modified
tests.
Please justify why no new tests are needed for this
patch.
Also please list what manual steps were performed to
verify this patch.
-1 patch. The patch command could not apply the patch.
Console output:
https://builds.apache.org/job/PreCommit-ZOOKEEPER-Build/1532//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
> Attachments:
> 0001-RFC-Don-t-tear-down-an-Observer-when-we-lose-connect.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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