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From "Andrew Stitcher (JIRA)" <qpid-...@incubator.apache.org>
Subject [jira] Commented: (QPID-2367) Early Initialization of File Descriptors Conflicts With Daemon Best Practices
Date Thu, 28 Jan 2010 15:45:34 GMT

    [ https://issues.apache.org/jira/browse/QPID-2367?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12805963#action_12805963

Andrew Stitcher commented on QPID-2367:

I think the fix most in line with the current code would be to use a singleton pattern.

However when you add all the possibilities of forking into the mix of how this code is used
I wonder if this would catch all the cases.

For instance what about a process that uses amqp then forks a daemon and then uses amqp in
the forked daemon? Is that a meaningful scenario? If it is you'd run into the same issue again.
Which implies that although it appears wasteful a class member might be needed.

> Early Initialization of File Descriptors Conflicts With Daemon Best Practices
> -----------------------------------------------------------------------------
>                 Key: QPID-2367
>                 URL: https://issues.apache.org/jira/browse/QPID-2367
>             Project: Qpid
>          Issue Type: Improvement
>          Components: C++ Client
>    Affects Versions: 0.5
>         Environment: Linux (possibly all UNIX), c++, g++
>            Reporter: Jason Schlauch
> At least one file descriptor (in qpid/sys/epoll/EpollPoller.*) in the c++ client is global
and declared as static.  In programs linked against the c++ qpid libs g++ generates code for
allocation and, more importantly, initialization of these descriptors that occurs before main().
 You can confirm this with gdb by breakpointing both the initialization and main() (the initialization
break is hit first).
> On the other hand, the canonical recipe for creating a UNIX daemon calls for the closing
of all open file descriptors after fork()ing (where the fork() certainly occurs after main()).
 While not an absolute requirement, closing all open file descriptors is considered a best
practice.  A loop to close all descriptors is also common in boilerplate daemon creation code
and has undoubtedly been cut-and-pasted into numerous daemons.
> The net effect is that the typical daemon will close the file descriptor opened before
main() in the c++ client library.  In the case of the epoll code this manifests as an inability
to connect to the broker.
> A fix for this would be to defer the initialization of the file descriptor (perhaps via
the Singleton pattern or a move of the variables into a class member).

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