Wei-Chiu Chuang created HDFS-11022:
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Summary: DataNode unable to remove corrupt block replica due to
race condition
Key: HDFS-11022
URL: https://issues.apache.org/jira/browse/HDFS-11022
Project: Hadoop HDFS
Issue Type: Bug
Components: datanode, namenode
Affects Versions: 2.6.0
Environment: CDH5.7.0
Reporter: Wei-Chiu Chuang
Priority: Critical
Scenario:
# A client reads a replica blk_A_x from a data node and detected corruption.
# In the meantime, the replica is appended, updating its generation stamp from
x to y.
# The client tells NN to mark the replica blk_A_x corrupt.
# NN tells the data node to (1) delete replica blk_A_x and (2) replicate the
newer replica blk_A_y from another datanode. Due to block placement policy,
blk_A_y is replicated to the same node. (It's a small cluster)
# DN is unable to receive the newer replica blk_A_y, because the replica
already exists.
# DN is also unable to delete replica blk_A_y because blk_A_y does not exist.
# The replica on the DN is not part of data pipeline, so it becomes stale.
If another replica becomes corrupt and NameNode wants to replicate a healthy
replica to this DataNode, it can't, because a stale replica exists. Because
this is a small cluster, soon enough (in a matter of a hour) no DataNode is
able to receive a healthy replica.
This cluster also suffers from HDFS-11019, so even though DataNode later
detected data corruption, it was unable to report to NameNode.
Note that we are still investigating the root cause of the corruption.
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