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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