[jira] [Created] (HDFS-12748) Standby NameNode memory leak when accessing webhdfs GETHOMEDIRECTORY

["Jiandan Yang (JIRA)" <ji...@apache.org>]

Jiandan Yang  created HDFS-12748:
------------------------------------

             Summary: Standby NameNode memory leak when accessing webhdfs GETHOMEDIRECTORY
                 Key: HDFS-12748
                 URL: https://issues.apache.org/jira/browse/HDFS-12748
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: hdfs
    Affects Versions: 2.8.2
            Reporter: Jiandan Yang 


In our production environment, the standby NN often do fullgc, through mat we found the largest object is FileSystem$Cache, which contains 7,844,890 DistributedFileSystem.
By view hierarchy of method FileSystem.get() , I found only NamenodeWebHdfsMethods#get call FileSystem.get(). I don't know why creating different DistributedFileSystem every time instead of get a FileSystem from cache.

{code:java}
    case GETHOMEDIRECTORY: {
      final String js = JsonUtil.toJsonString("Path",
          FileSystem.get(conf != null ? conf : new Configuration())
              .getHomeDirectory().toUri().getPath());
      return Response.ok(js).type(MediaType.APPLICATION_JSON).build();
    }
{code}
When we close FileSystem when GETHOMEDIRECTORY, NN don't do fullgc.

{code:java}
    case GETHOMEDIRECTORY: {
      FileSystem fs = null;
      try {
        fs = FileSystem.get(conf != null ? conf : new Configuration());
        final String js = JsonUtil.toJsonString("Path",
            fs.getHomeDirectory().toUri().getPath());
        return Response.ok(js).type(MediaType.APPLICATION_JSON).build();
      } finally {
        if (fs != null) {
          fs.close();
        }
      }
    }
{code}




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