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From "Wei-Chiu Chuang (Jira)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-16461) Regression: FileSystem cache lock parses XML within the lock
Date Tue, 01 Oct 2019 00:07:00 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-16461?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Wei-Chiu Chuang updated HADOOP-16461:
-------------------------------------
    Fix Version/s: 3.2.2
                   3.1.4

> Regression: FileSystem cache lock parses XML within the lock
> ------------------------------------------------------------
>
>                 Key: HADOOP-16461
>                 URL: https://issues.apache.org/jira/browse/HADOOP-16461
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: fs
>    Affects Versions: 3.3.0
>            Reporter: Gopal Vijayaraghavan
>            Assignee: Gopal Vijayaraghavan
>            Priority: Major
>             Fix For: 3.3.0, 3.1.4, 3.2.2
>
>
> https://github.com/apache/hadoop/blob/2546e6ece240924af2188bb39b3954a4896e4a4f/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FileSystem.java#L3388
> {code}
>       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()
>                 && !ShutdownHookManager.get().isShutdownInProgress()) {
>           ShutdownHookManager.get().addShutdownHook(clientFinalizer, SHUTDOWN_HOOK_PRIORITY);
>         }
>         fs.key = key;
>         map.put(key, fs);
>         if (conf.getBoolean(
>             FS_AUTOMATIC_CLOSE_KEY, FS_AUTOMATIC_CLOSE_DEFAULT)) {
>           toAutoClose.add(key);
>         }
>         return fs;
>       }
> {code}
> The lock now has a ShutdownHook creation, which ends up doing 
> https://github.com/apache/hadoop/blob/2546e6ece240924af2188bb39b3954a4896e4a4f/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/ShutdownHookManager.java#L205
> {code}
>     HookEntry(Runnable hook, int priority) {
>       this(hook, priority,
>           getShutdownTimeout(new Configuration()),
>           TIME_UNIT_DEFAULT);
>     }
> {code}
> which ends up doing a "new Configuration()" within the locked section.
> This indirectly hurts the cache hit scenarios as well, since if the lock on this is held,
then the other section cannot be entered either.
> https://github.com/apache/tez/blob/master/tez-runtime-library/src/main/java/org/apache/tez/runtime/library/common/sort/impl/TezSpillRecord.java#L65
> {code}
> I/O Setup 0 State: BLOCKED CPU usage on sample: 6ms
> org.apache.hadoop.fs.FileSystem$Cache.getInternal(URI, Configuration, FileSystem$Cache$Key)
FileSystem.java:3345
> org.apache.hadoop.fs.FileSystem$Cache.get(URI, Configuration) FileSystem.java:3320
> org.apache.hadoop.fs.FileSystem.get(URI, Configuration) FileSystem.java:479
> org.apache.hadoop.fs.FileSystem.getLocal(Configuration) FileSystem.java:435
> {code}
> slowing down the RawLocalFileSystem when there are other threads creating HDFS FileSystem
objects at the same time.



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