mod_fcgid: fcgi processes can fail to be collected and become zombies

["Shisei Nakano" <nakano@xxxxxxxxxx>]

Hello,

I found an issue in mod_fcgid; when a lot of pending requests are
piled up due to fcgi programs running too slow, the fcgi processes can
fail to be collected by mod_fcgid and become zombies. And if the
number of such zombies gets higher, the httpd itself terminates.

http://httpd.apache.org/mod_fcgid/mod/mod_fcgid.html#examples

I tried the example programs in the page above, both PHP and Perl
scripts, with sleep(3) inserted to make them slow. I could reproduce
the problem by requesting those programs 800 times per minute (with 20
threads, each requesting 40 times per minute).

Zombies were still not collected even if I set
"FcgidZombieScanInterval 3" explicitly.

Versions which reproduces the issue:
Apache 2.4.16, mod_fcgid 2.3.9, CentOS6.6
Apache 2.4.10, mod_fcgid 2.3.7, CentOS6.6

Versions which don't reproduce the issue:
Apache 2.2.25, mod_fcgid 2.3.7, CentOS6.6

My configuration for mod_fcgid:

    FcgidMaxProcessesPerClass 200

    FcgidIOTimeout   300
    FcgidIdleTimeout 180

    FcgidIPCDir           /home/www/var/apache24/fcgidsock
    FcgidProcessTableFile /home/www/var/apache24/fcgid_shm

    # 128MiB.
    FcgidMaxRequestLen 134217728

For now I am periodically graceful-restarting the httpd to collect
zombies. Please let me know if there is a better way to avoid this
problem.

Thanks,



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