[ 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: ---------------------------------------------------------------- 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.. -- This message was sent by Atlassian Jira (v8.3.4#803005) --------------------------------------------------------------------- To unsubscribe, e-mail: commits-unsubscr...@cassandra.apache.org For additional commands, e-mail: commits-h...@cassandra.apache.org