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Posted to commits@cassandra.apache.org by "ZhaoYang (Jira)" <ji...@apache.org> on 2020/06/18 13:45:00 UTC
[jira] [Comment Edited] (CASSANDRA-15752) Range read concurrency
factor didn't consider range merger
[ https://issues.apache.org/jira/browse/CASSANDRA-15752?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17139400#comment-17139400 ]
ZhaoYang edited comment on CASSANDRA-15752 at 6/18/20, 1:44 PM:
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backported to 3.0 and 3.11
|[trunk|https://github.com/apache/cassandra/pull/606/files]| [circle|https://circleci.com/workflow-run/440126c4-058d-4511-8301-16df2bddf5db]|
|[3.11|https://github.com/apache/cassandra/pull/643/files]| [circle|https://circleci.com/workflow-run/000e8712-3259-42c1-a2b3-20ff166fe5b4] |
|[3.0|https://github.com/apache/cassandra/pull/644] | [circle|https://circleci.com/workflow-run/3714cc8b-c0ef-4974-9b6a-d8ea815aaaea] |
was (Author: jasonstack):
backported to 3.0 and 3.11
|[trunk|https://github.com/apache/cassandra/pull/606/files]| [circle|https://circleci.com/workflow-run/440126c4-058d-4511-8301-16df2bddf5db]|
|[3.11|https://github.com/apache/cassandra/pull/643/files]| CI-pending |
|[3.0|https://github.com/apache/cassandra/pull/644] | CI-pending |
> Range read concurrency factor didn't consider range merger
> ----------------------------------------------------------
>
> Key: CASSANDRA-15752
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15752
> Project: Cassandra
> Issue Type: Bug
> Components: Legacy/Coordination
> Reporter: ZhaoYang
> Assignee: ZhaoYang
> Priority: Normal
> Fix For: 3.0.x, 3.11.x, 4.0-beta
>
>
> During range read, coordinator computes concurrency factor which is the number of vnode ranges to contact in parallel for the next batch.
> But in {{RangeCommandIterator}}, vnode ranges are merged by {{RangeMerger}} if vnode ranges share enough replicas to satisfy consistency level. eg. vnode range [a,b) has replica n1,n2,n3 and vnode range [b,c) has replica n2,n3,n4, so they can be merged as range [a,c) with replica n2, n3 for Quorum.
> Currently it counts number of merged ranges towards concurrency factor. Coordinator may fetch more ranges than needed.
> ----
> Another issue is that when executing range read on table with very small amount of data, concurrency factor can be bumped to {{size of total vnode ranges}}, eg. 10k, depending on the num of vnodes and cluster size. As a result, coordinator will send large number of concurrent range requests, potentially slowing down the cluster.. We should cap the max concurrency factor..
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