Daryn Sharp created HDFS-12639:
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Summary: BPOfferService lock may stall all service actors
Key: HDFS-12639
URL: https://issues.apache.org/jira/browse/HDFS-12639
Project: Hadoop HDFS
Issue Type: Bug
Components: datanode
Affects Versions: 2.8.0
Reporter: Daryn Sharp
{{BPOfferService}} manages {{BPServiceActor}} instances for the active and
standby. It uses a RW lock to primarily protect registration information while
determining the active/standby from heartbeats.
Unfortunately the write lock is held during command processing. If an actor is
experiencing high latency processing commands, the other actor will neither be
able to register (blocked in createRegistration, setNamespaceInfo,
verifyAndSetNamespaceInfo) nor process heartbeats (blocked in
updateActorStatesFromHeartbeat).
The worst case scenario for processing commands while holding the lock is
re-registration. The actor will loop, catching and logging exceptions, leaving
the other actor blocked for an non-deterministic (possibly infinite) amount of
time.
The lock must not be held during command processing.
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