Gergo Repas created YARN-7913:
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Summary: Improve error handling when application recovery fails
with exception
Key: YARN-7913
URL: https://issues.apache.org/jira/browse/YARN-7913
Project: Hadoop YARN
Issue Type: Improvement
Components: resourcemanager
Affects Versions: 3.0.0
Reporter: Gergo Repas
Assignee: Gergo Repas
There are edge cases when the application recovery fails with an exception.
Example failure scenario:
* setup: a queue is a leaf queue in the primary RM's config and the same queue
is a parent queue in the secondary RM's config.
* When failover happens with this setup, the recovery will fail for
applications on this queue, and an APP_REJECTED event will be dispatched to the
async dispatcher. On the same thread (that handles the recovery), a
NullPointerException is thrown when the applicationAttempt is tried to be
recovered
(https://github.com/apache/hadoop/blob/55066cc53dc22b68f9ca55a0029741d6c846be0a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/FairScheduler.java#L494).
I don't see a good way to avoid the NPE in this scenario, because when the NPE
occurs the APP_REJECTED has not been processed yet, and we don't know that the
application recovery failed.
Currently the first exception will abort the recovery, and if there are X
applications, there will be ~X passive -> active RM transition attempts - the
passive -> active RM transition will only succeed when the last APP_REJECTED
event is processed on the async dispatcher thread.
_The point of this ticket is to improve the error handling and reduce the
number of passive -> active RM transition attempts (solving the above described
failure scenario isn't in scope)._
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