Eric Badger created TEZ-3696:
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Summary: Jobs can hang when both concurrency and speculation are
enabled
Key: TEZ-3696
URL: https://issues.apache.org/jira/browse/TEZ-3696
Project: Apache Tez
Issue Type: Bug
Reporter: Eric Badger
Assignee: Eric Badger
We can reproduce the hung job by doing the following:
1. Run a sleep job with a concurrency of 1, speculation enabled, and 3 tasks
{noformat}
HADOOP_CLASSPATH="$TEZ_HOME/*:$TEZ_HOME/lib/*:$TEZ_CONF_DIR" yarn jar
$TEZ_HOME/tez-tests-*.jar mrrsleep -Dtez.am.vertex.max-task-concurrency=1
-Dtez.am.speculation.enabled=true -Dtez.task.timeout-ms=60000 -m 3 -mt 60000
-ir 0 -irt 0 -r 0 -rt 0
{noformat}
2. Let the 1st task run to completion and then stop the 2nd task so that a
speculative attempt is scheduled. Once the speculative attempt is scheduled for
the 2nd task, continue the original attempt and let it complete.
{noformat}
kill -STOP <pid>
// wait a few seconds for a speculative attempt to kick off
kill -CONT <pid>
{noformat}
3. Kill the 3rd task, which will create a 2nd attempt
{noformat}
kill -9 <pid>
{noformat}
4. The next thing to be drawn off of the queue will be the speculative attempt
of the 2nd task. However, it is already completed, so it will just sit in the
final state and the job will hang.
Basically, for the failure to happen, the number of speculative tasks that are
scheduled, but not yet ran has to be >= the concurrency of the job and there
has to be at least 1 task failure.
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