Ming Ma created HDFS-7518:
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Summary: Heartbeat processing doesn't have to take FSN readLock
Key: HDFS-7518
URL: https://issues.apache.org/jira/browse/HDFS-7518
Project: Hadoop HDFS
Issue Type: Sub-task
Reporter: Ming Ma
NameNode takes global read lock when it process heartbeat RPCs from DataNodes.
This increases lock contention and could impact NN overall throughput. Given
Heartbeat processing needs to access data specific to the DataNode that invokes
the RPC; it could just synchronize on the specific DataNode and datanodeMap.
It looks like each DatanodeDescriptor already keeps its own recover blocks,
replication blocks and invalidate blocks. There are several places that needed
to be changed to remove FSN lock.
As mentioned in other jiras, we need to some mechanism to reason about the
correctness of the solution.
Thoughts?
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