ZhaoYang created CASSANDRA-15752: ------------------------------------ Summary: 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
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