Unbalanced replication target
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Key: HADOOP-3685
URL: https://issues.apache.org/jira/browse/HADOOP-3685
Project: Hadoop Core
Issue Type: Bug
Components: dfs
Affects Versions: 0.17.0
Reporter: Koji Noguchi
Priority: Critical
In HADOOP-3633, namenode was assigning some datanodes to receive hundreds of
blocks in a short period which caused datanodes to go out of memroy(threads).
Most of them were from remote rack.
Looking at the code,
{noformat}
166 chooseLocalRack(results.get(1), excludedNodes, blocksize,
167 maxNodesPerRack, results);
{noformat}
was sometimes not choosing the local rack of the writer(source).
As a result, when a datanode goes down, other datanodes on the same rack were
getting large number of blocks from remote racks.
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