Zhe Zhang created HDFS-10966:
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Summary: Enhance Dispatcher logic on deciding when to give up a
source DataNode
Key: HDFS-10966
URL: https://issues.apache.org/jira/browse/HDFS-10966
Project: Hadoop HDFS
Issue Type: Bug
Components: balancer & mover
Reporter: Zhe Zhang
Assignee: Mark Wagner
When a {{Dispatcher}} thread works on a source DataNode, in each iteration it
tries to execute a {{PendingMove}}. If no block is moved after 5 iterations,
this source (over-utlized) DataNode is given up for this Balancer iteration (20
mins). This is problematic if the source DataNode was heavily loaded in the
beginning of the iteration. It will quickly encounter 5 unsuccessful moves and
be abandoned.
We should enhance this logic by e.g. using elapsed time instead of number of
iterations.
{code}
// Check if the previous move was successful
} else {
// source node cannot find a pending block to move, iteration +1
noPendingMoveIteration++;
// in case no blocks can be moved for source node's task,
// jump out of while-loop after 5 iterations.
if (noPendingMoveIteration >= MAX_NO_PENDING_MOVE_ITERATIONS) {
LOG.info("Failed to find a pending move " + noPendingMoveIteration
+ " times. Skipping " + this);
resetScheduledSize();
}
}
{code}
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