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https://issues.apache.org/jira/browse/HDFS-14295?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16778790#comment-16778790
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Íñigo Goiri commented on HDFS-14295:
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Thanks [~belugabehr] for the clarification.
I agree that there is no point on actually tracking the 30 seconds as it is an
arbitrary number.
My concern is the possible delay on tasks that were done right away before.
Can we do the shutdown() at the beginning and then shutdownNow() at the end
without waiting at all?
The old threads were just Daemons and they were find to be killed.
Is there an equivalent to make the execution service spawn daemon threads?
> Add Threadpool for DataTransfers
> --------------------------------
>
> Key: HDFS-14295
> URL: https://issues.apache.org/jira/browse/HDFS-14295
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: datanode
> Affects Versions: 3.2.0
> Reporter: BELUGA BEHR
> Assignee: BELUGA BEHR
> Priority: Major
> Attachments: HDFS-14295.1.patch, HDFS-14295.2.patch,
> HDFS-14295.3.patch, HDFS-14295.4.patch, HDFS-14295.5.patch,
> HDFS-14295.6.patch, HDFS-14295.7.patch, HDFS-14295.8.patch
>
>
> When a DataNode data transfers a block, is spins up a new thread for each
> transfer.
> [Here|https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java#L2339]
> and
> [Here|https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java#L3019-L3022].
> Instead, add the threads to a {{CachedThreadPool}} so that when their
> threads complete the transfer, they can be re-used for another transfer. This
> should save resources spent on creating and spinning up transfer threads.
> One thing I'll point out that's a bit off, which I address in this patch, ...
> There are two places in the code where a {{DataTransfer}} thread is started.
> In [one
> place|https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java#L2339-L2341],
> it's started in a default thread group. In [another
> place|https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java#L3019-L3022],
> it's started in the
> [dataXceiverServer|https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java#L1164]
> thread group.
> I do not think it's correct to include any of these threads in the
> {{dataXceiverServer}} thread group. Anything submitted to the
> {{dataXceiverServer}} should probably be tied to the
> {{dfs.datanode.max.transfer.threads}} configurations, and neither of these
> methods are. Instead, they should be submitted into the same thread pool with
> its own thread group (probably the default thread group, unless someone
> suggests otherwise) and is what I have included in this patch.
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