Oozie job in PREP state for a long time

[Dongying Jiao]

Hi:
I have a oozie coordinator job run at 02:00 o'clock everyday, sometimes,
the job can run smoothly, but sometimes, the job is stuck in PREP state for
a long time.

This is my part of my coordinator.xml:
<coordinator-app name="CoordinatorForETL"
  frequency="${coordinatorFrequency}"
  start="${startTime}" end="${endTime}" timezone="America/New_York"
  xmlns="uri:oozie:coordinator:0.2">
  <controls>
    <timeout>10</timeout>
    <concurrency>1</concurrency>
  </controls>
  <action>
    <workflow>
.............
This is part of the workflow.xml:
......
<start to="flowDecision"/>
  <decision name="flowDecision">
  <switch>
    <case to="q1">${workflowType eq "etl" || workflowType eq "all"}</case>
    <case to="prediction">${workflowType eq "prediction"}</case>
    <case to="errorOnDecision">${workflowType eq "cleaning"}</case>
    <default to="errorOnDecision"/>
  </switch>
   </decision>
.......

>From my latest run, the job in PREP state for about 30 min. From oozie log,
the "start" node of the job is done at 02:00, but until 02:32, the
"flowDecision" node started to execute. During that period, I can see other
oozie jobs are running from log, but didn't find any error or exception in
log.

>From my understanding, oozie job in PREP state means the job is not
submitted to yarn yet, so can't find application id on yarn.
I wonder if this relates to oozie queue mechanism or concurrency control.
If yes, do you have experience on how to tune them?

Thanks a lot.

Best Regards,
Dong Ying