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Posted to issues@impala.apache.org by "Tim Armstrong (JIRA)" <ji...@apache.org> on 2017/11/01 19:31:02 UTC
[jira] [Created] (IMPALA-6140) Unexplained gap between "All
backends started" and "Rows available"
Tim Armstrong created IMPALA-6140:
-------------------------------------
Summary: Unexplained gap between "All backends started" and "Rows available"
Key: IMPALA-6140
URL: https://issues.apache.org/jira/browse/IMPALA-6140
Project: IMPALA
Issue Type: Bug
Components: Distributed Exec
Affects Versions: Impala 2.10.0
Reporter: Tim Armstrong
Priority: Major
In the query timeline below there is a significant delay before rows are available.
{noformat}
Query Timeline
Query submitted: 305.17us (305173)
Planning finished: 81ms (81195593)
Submit for admission: 82ms (82781362)
Completed admission: 83ms (83014912)
Ready to start on 35 backends: 84ms (84726950)
All 35 execution backends (35 fragment instances) started: 327ms (327067351)
Rows available: 1.0m (60347008871)
Unregister query: 7.5m (447851216220)
{noformat}
The exec summary doesn't have any evidence of slowness. I also looked at the rest of the profile and couldn't find any timers > 5s.
{noformat}
Operator #Hosts Avg Time Max Time #Rows Est. #Rows Peak Mem Est. Peak Mem Detail
------------------------------------------------------------------------------------------------------------------
03:AGGREGATE 1 0.000ns 0.000ns 0 1 148.00 KB 10.00 MB FINALIZE
02:EXCHANGE 1 474.937ms 474.937ms 33 1 0 0 UNPARTITIONED
01:AGGREGATE 34 64.749ms 453.860ms 33 1 1.24 MB 10.00 MB
00:SCAN HDFS 34 1s391ms 5s736ms 987.15K 12.96B 82.19 MB 176.00 MB db.table
{noformat}
One interesting data point is that we have anecdotal evidence that there were orphaned query fragments sending reports on this cluster.
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