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Chris Nauroth commented on HDFS-5776: ------------------------------------- FYI, I've discovered that the {{DFSClient}} can hang infinitely if using hedged reads and all eligible datanodes die. This bug is present in 2.4.0. I've posted a patch on HDFS-6231 to fix it, hopefully for inclusion in 2.4.1. > Support 'hedged' reads in DFSClient > ----------------------------------- > > Key: HDFS-5776 > URL: https://issues.apache.org/jira/browse/HDFS-5776 > Project: Hadoop HDFS > Issue Type: Improvement > Components: hdfs-client > Affects Versions: 3.0.0 > Reporter: Liang Xie > Assignee: Liang Xie > Fix For: 2.4.0 > > Attachments: HDFS-5776-v10.txt, HDFS-5776-v11.txt, HDFS-5776-v12.txt, > HDFS-5776-v12.txt, HDFS-5776-v13.wip.txt, HDFS-5776-v14.txt, > HDFS-5776-v15.txt, HDFS-5776-v17.txt, HDFS-5776-v17.txt, HDFS-5776-v2.txt, > HDFS-5776-v3.txt, HDFS-5776-v4.txt, HDFS-5776-v5.txt, HDFS-5776-v6.txt, > HDFS-5776-v7.txt, HDFS-5776-v8.txt, HDFS-5776-v9.txt, HDFS-5776.txt, > HDFS-5776v18.txt, HDFS-5776v21-branch2.txt, HDFS-5776v21.txt > > > This is a placeholder of hdfs related stuff backport from > https://issues.apache.org/jira/browse/HBASE-7509 > The quorum read ability should be helpful especially to optimize read outliers > we can utilize "dfs.dfsclient.quorum.read.threshold.millis" & > "dfs.dfsclient.quorum.read.threadpool.size" to enable/disable the hedged read > ability from client side(e.g. HBase), and by using DFSQuorumReadMetrics, we > could export the interested metric valus into client system(e.g. HBase's > regionserver metric). > The core logic is in pread code path, we decide to goto the original > fetchBlockByteRange or the new introduced fetchBlockByteRangeSpeculative per > the above config items. -- This message was sent by Atlassian JIRA (v6.2#6252)