He Xiaoqiao created HDFS-13183:
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Summary: Standby NameNode process getBlocks request to reduce
Active load
Key: HDFS-13183
URL: https://issues.apache.org/jira/browse/HDFS-13183
Project: Hadoop HDFS
Issue Type: Improvement
Components: balancer & mover, namenode
Affects Versions: 2.7.5, 3.1.0, 2.9.1, 2.8.4, 3.0.2
Reporter: He Xiaoqiao
Assignee: He Xiaoqiao
The performance of Active NameNode could be impact when {{Balancer}} requests
#getBlocks, since query blocks of overly full DNs performance is extremely
inefficient currently. The main reason is {{NameNodeRpcServer#getBlocks}} hold
read lock for long time. In extreme case, all handlers of Active NameNode RPC
server are occupied by one reader {{NameNodeRpcServer#getBlocks}} and other
write operation calls, thus Active NameNode enter a state of false death for
number of seconds even for minutes.
The similar performance concerns of Balancer have reported by HDFS-9412,
HDFS-7967, etc.
If Standby NameNode can shoulder #getBlocks heavy burden, it could speed up the
progress of balancing and reduce performance impact to Active NameNode.
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