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HBase >> mail # user >> zk connection leak with TableInput/OutputFormat (CDH3b4, 0.90.1)

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Re: zk connection leak with TableInput/OutputFormat (CDH3b4, 0.90.1)
I am having this same problem. After every run of my map-reduce job which uses TableInputFormat, I am leaking one ZK connection. The connections that are not being cleaned up are connected to the node that submitted the job, not the cluster nodes.

I tried explicitly cleaning up the connection using HConnectionManager.deleteConnection(config, true) after the job runs, but this has no effect. ZK still retains one connection per job run and never releases it. Eventually I run out of ZK connections even if I set maxCnxns very high (e.g. 600).

This happened for me with CDH3B4 and is still happening with the CDH3 release.

On Mar 23, 2011, at 3:27 PM, Todd Lipcon wrote:

> Hi Dmitriy,
> Are you submitting these MR jobs on a cluster? Which machines are
> leaking the connections? Is it the cluster nodes or the node where you
> submitted the job?
> After a job is complete, the JVMs that ran the tasks should be
> completely torn down and thus should not be able to hang onto a
> connection.
> -Todd
> On Wed, Mar 23, 2011 at 2:24 PM, Dmitriy Lyubimov <[EMAIL PROTECTED]> wrote:
>> yes i am passing destroyProxy=true. But according to the code, it
>> doesn't affect closing zookeeper connection (it should be closed
>> anyway) but i  have +1 zk connection each time i run the MR job still.
>> -d
>> On Wed, Mar 23, 2011 at 2:22 PM, Ted Yu <[EMAIL PROTECTED]> wrote:
>>> I assume you passed true as second parameter to deleteConnection().
>>> On Wed, Mar 23, 2011 at 1:54 PM, Dmitriy Lyubimov <[EMAIL PROTECTED]> wrote:
>>>> Hi,
>>>> I am experiencing severe connection leak in my MR client that uses
>>>> Hbase as input/output . Every job that uses TableInputFormat leaks 1
>>>> zookeeper connection per run as evidenced by netstat.
>>>> I understand that the way HTable manages connections now is it creates
>>>> a new HBase (and also Zookeeper) connection per each instance of
>>>> Configuration it is initialized with. By looking at the code of the
>>>> TableInputFormat class, i see that it creates HTable in the front end
>>>> during configuration (of course, it probably needs to use it to
>>>> determine region splits).
>>>> Since i have to configure each job individually, i must create a new
>>>> instance of Configuration. Thus, i am not able to use shared HBase
>>>> connections (which i would prefer to, but there seems to be no way now
>>>> to do that).
>>>> So... after i run an instance of MR job, the hbase connection seems to
>>>> be leaked. It also leaks zk connection , which is a problem since
>>>> zookeeper instances have limits on how many connections can be made
>>>> from the same IP and eventually the client is not able to create any
>>>> new HTables anymore since it can't establish any new zookeeper
>>>> connections.
>>>> I tried to do explicit cleanup by calling
>>>> HConnectionManager.deleteConnection (Configuration) passing in the
>>>> configuration that i used to create MR job. Doesn't seem to work.
>>>> So.. Is there a way to run MR job with TableInputFormat without
>>>> leaking a connection? I am pretty sure i am not creating any HTables
>>>> in the client side. Or is it a bug? I spent several days now
>>>> investigation an issue but i am still not able to come up with a
>>>> workaround against zookeeper connection leaks in HBase MR jobs.
>>>> thank you very much.
>>>> -Dmitriy
> --
> Todd Lipcon
> Software Engineer, Cloudera