Oliver Peng wrote:
> Hi All:
>
> I write an event handler to start our daemon service. The problem is
> that once the event handler code finished, whole Nagios process keep
> hanging. I check the CPU usage is 100% and by using strace I can see
> a lot of following system call:
>
> read(5, 0xbf879450, 1023) = -1 EAGAIN (Resource
> temporarily unavailable)
>
> By checking the source code, I found the reason of this problem.
>
> Nagios main process create a pipe fd[5,6] and fork a child process.
> In this child process, it use popen to create pipe and invoke event
> handler script. Once child process get output from event handler
> script, it transfer it to main process by using fd 6. Because in
> popen function, it doesn't close fd 6 before invoking event handler
> script, fd 6 is inherited down to our daemon process. Because our
> daemon process doesn't close fd 6, Nagios main process keep getting
> EAGAIN.
>
> Suggestion:
>
> To fix this problem, I would suggest to fix two parts.
>
> 1 Don't use popen. Instead create pipe, fork child process and close
> all unused file descriptor before invoking event handler script.
>
> 2 In main process, set timeout for getting EAGAIN error code to
> avoid endless loop.
>
Thanks for the writeup of this problem. I'll look into it.
--
Andreas Ericsson [email protected]
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