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From "Bryan Keller (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-3792) TableInputFormat leaks ZK connections
Date Sat, 16 Apr 2011 12:09:06 GMT
TableInputFormat leaks ZK connections
-------------------------------------

                 Key: HBASE-3792
                 URL: https://issues.apache.org/jira/browse/HBASE-3792
             Project: HBase
          Issue Type: Bug
          Components: mapreduce
    Affects Versions: 0.90.1
         Environment: Java 1.6.0_24, Mac OS X 10.6.7
            Reporter: Bryan Keller


The TableInputFormat creates an HTable using a new Configuration object, and it never cleans
it up. When running a Mapper, the TableInputFormat is instantiated and the ZK connection is
created. While this connection is not explicitly cleaned up, the Mapper process eventually
exits and thus the connection is closed. Ideally the TableRecordReader would close the connection
in its close() method rather than relying on the process to die for connection cleanup. This
is fairly easy to implement by overriding TableRecordReader, and also overriding TableInputFormat
to specify the new record reader.

The leak occurs when the JobClient is initializing and needs to retrieves the splits. To get
the splits, it instantiates a TableInputFormat. Doing so creates a ZK connection that is never
cleaned up. Unlike the mapper, however, my job client process does not die. Thus the ZK connections
accumulate.

I was able to fix the problem by writing my own TableInputFormat that does not initialize
the HTable in the getConf() method and does not have an HTable member variable. Rather, it
has a variable for the table name. The HTable is instantiated where needed and then cleaned
up. For example, in the getSplits() method, I create the HTable, then close the connection
once the splits are retrieved. I also create the HTable when creating the record reader, and
I have a record reader that closes the connection when done.

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