Corrupted blocks get deleted but not replicated
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Key: HADOOP-1349
URL: https://issues.apache.org/jira/browse/HADOOP-1349
Project: Hadoop
Issue Type: Bug
Components: dfs
Reporter: Hairong Kuang
Fix For: 0.14.0
When I test the patch to HADOOP-1345 on a two node dfs cluster, I see that dfs
correctly delete the corrupted replica and successfully retry reading from the
other correct replica, but the block does not get replicated. The block remains
with only 1 replica until the next block report comes in.
In my testcase, since the dfs cluster has only 2 datanodes, the target of
replication is the same as the target of block invalidation. After poking the
logs, I found out that the namenode sent the replication request before the
block invalidation request.
This is because the namenode does not invalidate a block well. In
FSNamesystem.invalidateBlock, it first puts the invalidate request in a queue
and then immediately removes the replica from its state, which triggers the
choosing a target for the block. When requests are sent back to the target
datanode as a reply to a heartbeat message, the replication requests have
higher priority than the invalidate requests.
This problem could be solved if a namenode removes an invalidated replica from
its state only after the invalidate request is sent to the datanode.
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