add register cleanup utility to cli

[Kapil Thangavelu]

This bug is mostly relevant to the unit test runner, when running test loops, and has already been worked around.

To enable automatic cleanup of zookeeper clients. Some sort of global registry of cleanups in ensemble/control/command .. executed by the ensemble/command.Commander class on shutdown. and a common utility function for registering a client with it in control/utils.

[Jim Baker (jimbaker)]

This problem impacted trunk as of r193 due to the lack of cleanup exhausting connections. As a temporary measure, r194 changed the ZK config such that maxClientCnxns=0 (unlimited connections). In the future, we can test the effectiveness of a fix to this bug by reducing the max limit to a small number (presumably close to the parallelism of our tests, which currently is 1).

[Kapil Thangavelu (hazmat)]

Excerpts from Jim Baker's message of Fri Apr 08 18:50:19 UTC 2011:
> This problem impacted trunk as of r193 due to the lack of cleanup
> exhausting connections. As a temporary measure, r194 changed the ZK
> config such that maxClientCnxns=0 (unlimited connections). In the
> future, we can test the effectiveness of a fix to this bug by reducing
> the max limit to a small number (presumably close to the parallelism of
> our tests, which currently is 1).
>

Its a bit more than one, some tests do parallel connections, but point taken.

[Jim Baker (jimbaker)]

Indeed that was my expectation on a small number :)