BELUGA BEHR created HDFS-13978:
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Summary: Review of DiskBalancer
Key: HDFS-13978
URL: https://issues.apache.org/jira/browse/HDFS-13978
Project: Hadoop HDFS
Issue Type: Improvement
Components: datanode, hdfs
Affects Versions: 3.2.0
Environment: * Use ArrayList instead of LinkedList. Especially because
this code here uses the {{List#get()}} method, which is very slow for the
LinkedList since it has to traverse every node to get to the offset: O(N^2)
{code}
ExtendedBlock getNextBlock(List<FsVolumeSpi.BlockIterator> poolIters,
DiskBalancerWorkItem item) {
Preconditions.checkNotNull(poolIters);
int currentCount = 0;
ExtendedBlock block = null;
while (block == null && currentCount < poolIters.size()) {
currentCount++;
int index = poolIndex++ % poolIters.size();
FsVolumeSpi.BlockIterator currentPoolIter = poolIters.get(index);
block = getBlockToCopy(currentPoolIter, item);
}
{code}
* Do not "log and throw" errors. This is an anti-pattern and should be
avoided. Log or throw, but don't do both. Removed some logging
* Improved other logging statements
* Improved the {{hashcode}} method of one of the inner classes. It was
instantiating a List and performing iteration for every call. Replace with
Eclipse-generated hashcode method.
* Fixed compiler warnings for deprecated code or code that was not parameterized
* Fix check style issue
Reporter: BELUGA BEHR
Attachments: HDFS-13978.1.patch
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