datanode sending block reports to namenode once every second
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Key: HADOOP-1297
URL: https://issues.apache.org/jira/browse/HADOOP-1297
Project: Hadoop
Issue Type: Bug
Components: dfs
Reporter: dhruba borthakur
Assigned To: dhruba borthakur
The namenode is requesting a block to be deleted. The datanode tries this
operation and encounters an error because the block is not in the blockMap. The
processCommand() method raises an exception. The code is such that the variable
lastBlockReport is not set if processCommand() raises an exception. This means
that the datanode immediately send another block report to the namenode. The
eats up quite a bit of CPU on namenode.
In short, the above condition causes the datanode to send blockReports almost
once every second!
I propose that we do the following:
1. in Datanode.offerService, replace the following piece of code
DatanodeCommand cmd = namenode.blockReport(dnRegistration,
data.getBlockReport());
processCommand(cmd);
lastBlockReport = now;
with
DatanodeCommand cmd = namenode.blockReport(dnRegistration,
data.getBlockReport());
lastBlockReport = now;
processCommand(cmd);
2. In FSDataSet.invalidate:
a) continue to process all blocks in invalidBlks[] even if one in the middle
encounters a problem.
b) if getFile() returns null, still invoke volumeMap.get() and print whether we
found the block in
volumes or not. The volumeMap is used to generate the blockReport and this
might help in debugging.
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