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From Jonathan Simms <slyp...@gmail.com>
Subject Re: How to deal with fork() properly when using the zkc mt lib
Date Thu, 10 May 2012 23:11:49 GMT
Michi, fair point, I actually just looked into it, there doesn't seem
to be a way through the api to re-establish the session. If you call
zookeeper_close on the handle:

 "After this call, the client session will no longer be valid. The
function will flush any outstanding send requests before return. As a
result it may block."

I tried:

* establish session with handle A
* copy clientid_t from handle A
* zookeeper_close handle A
* construct handle B using clientid_t values from handle A

I get back a SESSION_EXPIRED from the server. (debug from mt lib here:
https://gist.github.com/3b7e4060746d03cef287)

It would be *really* useful if i could basically "suspend" a session
while i forked, then reconnect and pick up where i left off. Is this
not possible?

On Thu, May 10, 2012 at 6:41 PM, Michi Mutsuzaki <michi@cs.stanford.edu> wrote:
> Hi Jonathan,
>
> It would be very difficult to share multi-threaded zk handle with
> child process. I'm surprised it actually works on mac. I think saving
> session id/password and re-establishing the session in the child
> process is more robust and platform independent.
>
> Thanks!
> --Michi


>
> On Thu, May 10, 2012 at 12:45 PM, Jonathan Simms <slyphon@gmail.com> wrote:
>> Hi all,
>>
>> I'm the maintainer of the ruby zookeeper library, and I'm having
>> trouble getting consistent behavior when a user calls fork(). When
>> developing it on MacOS (using 3.3.5), I was able to fork, then
>> immediately call zookeeper_close() in the child, and then create a new
>> handle. Testing on Linux, the behavior is much more unpredictable.
>> Regularly, it seems there are segfaults when calling zookeeper_close.
>> https://gist.github.com/22338464cd47e0e50970
>>
>>
>> So I guess my question is, is there any safe way to fork() while the
>> client is running?
>>
>> Another possibility i thought of is to note the session id/passwd,
>> close the client, fork, then re-open with the same id/passwd to
>> re-establish the session in the parent.
>>
>> Any recommendations?

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