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https://issues.apache.org/jira/browse/TEZ-1562?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14128094#comment-14128094
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Hitesh Shah commented on TEZ-1562:
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[~rajesh.balamohan] In that case, I am not sure we can do much until we start
supporting running DAGs in parallel within the same AM.
> DAGImpl commitOrAbortOutputs takes long time (300+ seconds) for reducer
> vertex with 4000+ tasks
> -----------------------------------------------------------------------------------------------
>
> Key: TEZ-1562
> URL: https://issues.apache.org/jira/browse/TEZ-1562
> Project: Apache Tez
> Issue Type: Bug
> Reporter: Rajesh Balamohan
> Labels: performance
>
> M7 --> R1
> M2 --> R1
> I was running a job with 4000 reducers. This is in non-session mode.
> At the end of the job, it took 300+ seconds just to commit().
> It appears that its doing some cleanup work. But in session mode, this could
> lead to the following issue
> 1. Open session
> 2. Run small job1
> 3. Run large job1
> 4. Run small job2
> In this case, small job2 wouldn't even start running until large-job1's
> commit is over which would be in the order of 300+ seconds.
> Please refer to the logs here,
> 2014-09-09 17:58:20,422 INFO [AsyncDispatcher event handler]
> org.apache.tez.dag.app.dag.impl.DAGImpl: Vertex
> vertex_1409722953518_0143_1_02 completed., numCompletedVertices=3,
> numSuccessfulVertices=3, numFailedVertices=0, numKilledVertices=0,
> numVertices=3
> 2014-09-09 17:58:20,422 INFO [AsyncDispatcher event handler]
> org.apache.tez.dag.app.dag.impl.DAGImpl: Calling DAG commit/abort for dag:
> dag_1409722953518_0143_1
> 2014-09-09 17:58:20,426 INFO [AsyncDispatcher event handler]
> org.apache.tez.dag.app.dag.impl.DAGImpl: Committing output: Reducer_6_sink
> for vertex: vertex_1409722953518_0143_1_02
> 2014-09-09 18:03:25,207 INFO [AsyncDispatcher event handler]
> org.apache.tez.dag.app.dag.impl.DAGImpl: No output committers for vertex:
> Map_7
> 2014-09-09 18:03:25,207 INFO [AsyncDispatcher event handler]
> org.apache.tez.dag.app.dag.impl.DAGImpl: No output committers for vertex:
> Map_2
> 2014-09-09 18:03:25,207 INFO [AsyncDispatcher event handler]
> org.apache.tez.dag.app.dag.impl.DAGImpl: Patch : Time taken to
> commitOrAbortOutputs : 304784 <==== In milliseconds
> 2014-09-09 18:03:25,361 INFO [AsyncDispatcher event handler]
> org.apache.tez.dag.app.dag.impl.DAGImpl: Patch : Time taken to log jobhistory
> : 304938 <==== Cumulative number
> 2014-09-09 18:03:25,363 INFO [AsyncDispatcher event handler]
> org.apache.tez.dag.app.dag.impl.DAGImpl: Patch : Time taken to handle
> DAGAppMasterEventDAGFinished : 304940 <==== Cumulative number
> 2014-09-09 18:03:25,363 INFO [AsyncDispatcher event handler]
> org.apache.tez.dag.app.dag.impl.DAGImpl: DAG: dag_1409722953518_0143_1
> finished with state: SUCCEEDED
> 2014-09-09 18:03:25,363 INFO [AsyncDispatcher event handler]
> org.apache.tez.dag.app.dag.impl.DAGImpl: dag_1409722953518_0143_1
> transitioned from RUNNING to SUCCEEDED
> Should this operation be moved to a separate thread as the DAG is already
> marked as SUCCEEDED?
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