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Posted to hdfs-dev@hadoop.apache.org by "Lei (Eddy) Xu (JIRA)" <ji...@apache.org> on 2017/09/08 22:58:00 UTC
[jira] [Created] (HDFS-12412) Remove
ErasureCodingWorker.stripedReadPool
Lei (Eddy) Xu created HDFS-12412:
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Summary: Remove ErasureCodingWorker.stripedReadPool
Key: HDFS-12412
URL: https://issues.apache.org/jira/browse/HDFS-12412
Project: Hadoop HDFS
Issue Type: Improvement
Components: erasure-coding
Affects Versions: 3.0.0-alpha3
Reporter: Lei (Eddy) Xu
Assignee: Lei (Eddy) Xu
In {{ErasureCodingWorker}}, it uses {{stripedReconstructionPool}} to schedule the EC recovery tasks, while uses {{stripedReadPool}} for the reader threads in each recovery task. We only need one of them to throttle the speed of recovery process, because each EC recovery task has a fix number of source readers (i.e., 3 for RS(3,2)). And because of the findings in HDFS-12044, the speed of EC recovery can be throttled by {{strippedReconstructionPool}} with {{xmitsInProgress}}.
Moreover, keeping {{stripedReadPool}} makes customer difficult to understand and calculate the right balance between {{dfs.datanode.ec.reconstruction.stripedread.threads}}, {{dfs.datanode.ec.reconstruction.stripedblock.threads.size}} and {{maxReplicationStreams}}. For example, a small {{stripread.threads}} (comparing to which {{reconstruction.threads.size}} implies), will unnecessarily limit the speed of recovery, which leads to larger MTTR.
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