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https://issues.apache.org/jira/browse/KAFKA-4485?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15717277#comment-15717277
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ASF GitHub Bot commented on KAFKA-4485:
---------------------------------------
GitHub user lindong28 opened a pull request:
https://github.com/apache/kafka/pull/2208
KAFKA-4485; Follower should be in the isr if its FetchRequest has fetched
up to the logEndOffset of leader
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/lindong28/kafka KAFKA-4485
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/kafka/pull/2208.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #2208
----
commit c2c24839708ac0e60214f69606813d7aeff6ed21
Author: Dong Lin <[email protected]>
Date: 2016-12-03T03:32:59Z
KAFKA-4485; Follower should be in the isr if its FetchRequest has fetched
up to the logEndOffset of leader
----
> Follower should be in the isr if its FetchRequest has fetched up to the
> logEndOffset of leader
> ----------------------------------------------------------------------------------------------
>
> Key: KAFKA-4485
> URL: https://issues.apache.org/jira/browse/KAFKA-4485
> Project: Kafka
> Issue Type: Bug
> Reporter: Dong Lin
> Assignee: Dong Lin
>
> As of current implementation, we will exclude follower from ISR if the begin
> offset of FetchRequest from this follower is always smaller than logEndOffset
> of leader for more than replicaLagTimeMaxMs.
> Also, we will add a follower to ISR if the beginOffset of FetchRequest from
> this follower is equal or larger than high watermark of this partition.
> This is problematic for the following reasons:
> 1) The criteria for ISR is inconsistent between maybeExpandIsr() and
> maybeShrinkIsr(). A follower may be repeatedly remove and added to the ISR
> (e.g. in the scenario described below).
> 2) A follower may be removed from the ISR even if its fetch rate can keep up
> with produce rate. Suppose a produce keeps producing a lot of small requests
> at high request but low byte rate, the fetch request is always able to read
> all the available data at the time leader receives it. However, the begin
> offset of fetch request will always be smaller than logEndOffset of leader.
> Thus the follower will be removed from ISR.
> The solution to the problem is the following:
> A follower should be in ISR if begin offset of its FetchRequest >= max(high
> watermark of partition, log end offset of leader at the time the leader
> receives the previous FetchRequest). The follower should be removed from ISR
> if this criteria is not met for more than replicaLagTimeMaxMs.
> This solution makes the following guarantee:
> 1) If a follower is in ISR, then its log end offset >= high watermark of
> partition at least sometime in the last replicaLagTimeMaxMs.
> 2) If a follower is not in ISR, then the end offset of its FetchRequest can
> not catch up with log end offset of leader for more than replicaLagTimeMaxMs.
> Either follower is in bootstrap phase, or the follower's average fetch rate <
> produce rate into the partition for more than replicaLagTimeMaxMs.
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