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https://issues.apache.org/jira/browse/HDFS-4309?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13531589#comment-13531589
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Aaron T. Myers commented on HDFS-4309:
--------------------------------------
Hi MaWenJin, it's a little tough for me to follow the patch you've attached,
since it appears to both introduce tabs instead of spaces, and because it
appears to make whitespace changes on lines that are otherwise unchanged. Could
you please attach a new patch which doesn't include hard tabs and only changes
the pertinent lines? Additionally, please make sure that the patch you upload
applies cleanly to Hadoop trunk. The reason the QA bot failed to apply the
patch is probably because it was generated against a different branch than
trunk.
> Multithreaded get through the Cache FileSystem Object to lead LeaseChecker
> memory leak
> --------------------------------------------------------------------------------------
>
> Key: HDFS-4309
> URL: https://issues.apache.org/jira/browse/HDFS-4309
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: hdfs-client
> Affects Versions: 0.20.205.0, 0.23.1, 0.23.4, 2.0.1-alpha, 2.0.2-alpha
> Reporter: MaWenJin
> Labels: patch
> Attachments: HDFS-4309.patch, jmap2.log
>
> Original Estimate: 204h
> Remaining Estimate: 204h
>
> If multiple threads concurrently execute the following methods will result in
> the thread fs = createFileSystem (uri, conf) method is called.And create
> multiple DFSClient, start at the same time LeaseChecker daemon thread, may
> not be able to use shutdownhook close it after the process, resulting in a
> memory leak.
> private FileSystem getInternal(URI uri, Configuration conf, Key key) throws
> IOException{
> FileSystem fs = null;
> synchronized (this) {
> fs = map.get(key);
> }
> if (fs != null) {
> return fs;
> }
> // this is
> fs = createFileSystem(uri, conf);
> synchronized (this) { // refetch the lock again
> FileSystem oldfs = map.get(key);
> if (oldfs != null) { // a file system is created while lock is
> releasing
> fs.close(); // close the new file system
> return oldfs; // return the old file system
> }
> // now insert the new file system into the map
> if (map.isEmpty() && !clientFinalizer.isAlive()) {
> Runtime.getRuntime().addShutdownHook(clientFinalizer);
> }
> fs.key = key;
> map.put(key, fs);
> if (conf.getBoolean("fs.automatic.close", true)) {
> toAutoClose.add(key);
> }
> return fs;
> }
> }
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