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https://issues.apache.org/jira/browse/HDFS-14292?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16925162#comment-16925162
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Hadoop QA commented on HDFS-14292:
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| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:blue}0{color} | {color:blue} reexec {color} | {color:blue} 0m
0s{color} | {color:blue} Docker mode activated. {color} |
| {color:red}-1{color} | {color:red} patch {color} | {color:red} 0m 9s{color}
| {color:red} HDFS-14292 does not apply to trunk. Rebase required? Wrong
Branch? See https://wiki.apache.org/hadoop/HowToContribute for help. {color} |
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|| Subsystem || Report/Notes ||
| JIRA Issue | HDFS-14292 |
| JIRA Patch URL |
https://issues.apache.org/jira/secure/attachment/12960370/HDFS-14292.8.patch |
| Console output |
https://builds.apache.org/job/PreCommit-HDFS-Build/27817/console |
| Powered by | Apache Yetus 0.8.0 http://yetus.apache.org |
This message was automatically generated.
> Introduce Java ExecutorService to DataXceiverServer
> ---------------------------------------------------
>
> Key: HDFS-14292
> URL: https://issues.apache.org/jira/browse/HDFS-14292
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: datanode
> Affects Versions: 3.2.0
> Reporter: David Mollitor
> Assignee: David Mollitor
> Priority: Major
> Attachments: HDFS-14292.1.patch, HDFS-14292.2.patch,
> HDFS-14292.3.patch, HDFS-14292.4.patch, HDFS-14292.5.patch,
> HDFS-14292.6.patch, HDFS-14292.7.patch, HDFS-14292.8.patch, HDFS-14292.8.patch
>
>
> I wanted to investigate {{dfs.datanode.max.transfer.threads}} from
> {{hdfs-site.xml}}. It is described as "Specifies the maximum number of
> threads to use for transferring data in and out of the DN." The default
> value is 4096. I found it interesting because 4096 threads sounds like a lot
> to me. I'm not sure how a system with 8-16 cores would react to this large a
> thread count. Intuitively, I would say that the overhead of context
> switching would be immense.
> During my investigation, I discovered the
> [following|https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataXceiverServer.java#L203-L216]
> setup in the {{DataXceiverServer}} class:
> # A peer connects to a DataNode
> # A new thread is spun up to service this connection
> # The thread runs to completion
> # The tread dies
> It would perhaps be better if we used a thread pool to better manage the
> lifecycle of the service threads and to allow the DataNode to re-use existing
> threads, saving on the need to create and spin-up threads on demand.
> In this JIRA, I have added a couple of things:
> # Added a thread pool to {{DataXceiverServer}} class that, on demand, will
> create up to {{dfs.datanode.max.transfer.threads}}. A thread that has
> completed its prior duties will stay idle for up to 60 seconds
> (configurable), it will be retired if no new work has arrived.
> # Added new methods to the {{Peer}} Interface to allow for better logging and
> less code within each Thread ({{DataXceiver}}).
> # Updated the Thread code ({{DataXceiver}}) regarding its interactions with
> {{blockReceiver}} instance variable
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