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https://issues.apache.org/jira/browse/ZOOKEEPER-1413?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13691861#comment-13691861
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Flavio Junqueira commented on ZOOKEEPER-1413:
---------------------------------------------
+1, thanks, Thawan. There is one caveat, though, the license header seems to be
missing in TxnLogProposalIterator. The one who commits it needs to remember to
add the license header, and upload the patch that has been committed.
Do you want to try to commit this one to check that your accounting setting is
ok, Thawan? Please don't forget to edit CHANGES.txt and to add new files.
Also, it would be good if we decide what to do with ZOOKEEPER-876. My take is
that we should resolve it and explain there that there is a corner case that we
are not covering in here.
> Use on-disk transaction log for learner sync up
> -----------------------------------------------
>
> Key: ZOOKEEPER-1413
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1413
> Project: ZooKeeper
> Issue Type: Improvement
> Components: server
> Affects Versions: 3.4.3
> Reporter: Thawan Kooburat
> Assignee: Thawan Kooburat
> Priority: Minor
> Labels: performance
> Fix For: 3.5.0
>
> Attachments: ZOOKEEPER-1413.patch, ZOOKEEPER-1413.patch,
> ZOOKEEPER-1413.patch, ZOOKEEPER-1413.patch, ZOOKEEPER-1413.patch,
> ZOOKEEPER-1413.patch
>
>
> Motivation:
> The learner syncs up with leader by retrieving committed log from the leader.
> Currently, the leader only keeps 500 entries of recently committed log in
> memory. If the learner falls behind more than 500 updates, the leader will
> send the entire snapshot to the learner.
> With the size of the snapshot for some of our Zookeeper deployments (~10G),
> it is prohibitively expensive to send the entire snapshot over network.
> Additionally, our Zookeeper may serve more than 4K updates per seconds. As a
> result, a network hiccups for less than a second will cause the learner to
> use snapshot transfer.
> Design:
> Instead of looking only at committed log in memory, the leader will also look
> at transaction log on disk. The amount of transaction log kept on disk is
> configurable and the current default is 100k. This will allow Zookeeper to
> tolerate longer temporal network failure before initiating the snapshot
> transfer.
> Implementation:
> We plan to add interface to the persistence layer will can be use to retrieve
> proposals from on-disk transaction log. These proposals can then be used to
> send to the learner using existing protocol.
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