[ https://issues.apache.org/jira/browse/CASSANDRA-15752?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
ZhaoYang updated CASSANDRA-15752: --------------------------------- Source Control Link: trunk: https://github.com/apache/cassandra/pull/606 Test and Documentation Plan: Added unit tests. Circle Ci: https://app.circleci.com/pipelines/github/jasonstack/cassandra/153/workflows/39d0da06-96dc-4795-aa39-e4f428ba8ea7 [Trunk Patch|https://github.com/apache/cassandra/pull/606] / [CI|https://app.circleci.com/pipelines/github/jasonstack/cassandra/153/workflows/39d0da06-96dc-4795-aa39-e4f428ba8ea7]: * count vnode ranges instead of merged ranges against concurrency factor during range read * cap max concurrency factor as ten times the number of cores to avoid large number of concurrent remote ranges in large vnode cluster. > 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.x > > > 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