Ted Yu created HDFS-4796:
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Summary: Port HDFS-4721 'Speed up lease/block recovery when DN
fails and a block goes into recovery' to branch 1
Key: HDFS-4796
URL: https://issues.apache.org/jira/browse/HDFS-4796
Project: Hadoop HDFS
Issue Type: Bug
Reporter: Ted Yu
This was observed while doing HBase WAL recovery. HBase uses append to write to
its write ahead log. So initially the pipeline is setup as
DN1 --> DN2 --> DN3
This WAL needs to be read when DN1 fails since it houses the HBase regionserver
for the WAL.
HBase first recovers the lease on the WAL file. During recovery, we choose DN1
as the primary DN to do the recovery even though DN1 has failed and is not
heartbeating any more.
To speedup lease/block recovery, we always choose the datanode with the most
recent heartbeat.
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