Tsz Wo Nicholas Sze created HDFS-9434:
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Summary: Recommission a datanode with 500k blocks may pause NN for
30 seconds
Key: HDFS-9434
URL: https://issues.apache.org/jira/browse/HDFS-9434
Project: Hadoop HDFS
Issue Type: Improvement
Components: namenode
Reporter: Tsz Wo Nicholas Sze
Assignee: Tsz Wo Nicholas Sze
In BlockManager, processOverReplicatedBlocksOnReCommission is called within the
namespace lock. There is a (not very useful) log message printed in
processOverReplicatedBlock. When there is a large number of blocks stored in a
storage, printing the log message for each block can pause NN to process any
other operations. We did see that it could pause NN for 30 seconds for a
storage with 500k blocks.
I suggest to change the log message to trace level as a quick fix.
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