[ https://issues.apache.org/jira/browse/HDFS-9081?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
He Tianyi updated HDFS-9081: ---------------------------- Summary: False-positive ACK slow log in DFSClient (was: False-positive of ACK slow log in DFSClient) > False-positive ACK slow log in DFSClient > ---------------------------------------- > > Key: HDFS-9081 > URL: https://issues.apache.org/jira/browse/HDFS-9081 > Project: Hadoop HDFS > Issue Type: Bug > Affects Versions: 2.6.0 > Reporter: He Tianyi > Assignee: He Tianyi > Priority: Minor > > This issue is related with code below: > {noformat} > if (duration > dfsclientSlowLogThresholdMs > && ack.getSeqno() != Packet.HEART_BEAT_SEQNO) { > DFSClient.LOG > .warn("Slow ReadProcessor read fields took " + duration > + "ms (threshold=" + dfsclientSlowLogThresholdMs + "ms); ack: " > + ack + ", targets: " + Arrays.asList(targets)); > } else if (DFSClient.LOG.isDebugEnabled()) { > DFSClient.LOG.debug("DFSClient " + ack); > } > {noformat} > DFSClient prints slow log when awaited after unexpected amount of time > (usually 30000 ms). This is a good indicator for network or I/O performance > issue. > However, there is scenario that this slow log is false-positive, i.e. a > reducer, (StageA) iterates over records with identical key, this takes > arbitrary amount of time, but generates no output. (StageB) Then, it output > arbitrary number of records when meet a different key. > If one StageA lasts more than 30000 ms (as the example above), there will be > one or more slow log generated, which is not related to any HDFS performance > issue. > In general cases, user should not expect this, as they could be misguided. -- This message was sent by Atlassian JIRA (v6.3.4#6332)