Apache::SizeLimit - Because size does matter. |
Apache::SizeLimit - Because size does matter.
This module allows you to kill off Apache httpd processes if they grow too large. You can choose to set up the process size limiter to check the process size on every request:
# in your startup.pl: use Apache::SizeLimit; $Apache::SizeLimit::MAX_PROCESS_SIZE = 10000; # in KB, so this is 10MB
# in your httpd.conf: PerlFixupHandler Apache::SizeLimit # you can set this up as any Perl*Handler that handles part of the # request, even the LogHandler will do.
Or you can just check those requests that are likely to get big, such as CGI requests. This way of checking is also easier for those who are mostly just running CGI.pm/Registry scripts:
# in your CGI: use Apache::SizeLimit; &Apache::SizeLimit::setmax(10000); # Max Process Size in KB
Since checking the process size can take a few system calls on some platforms (e.g. linux), you may want to only check the process size every N times. To do so, put this in your startup.pl or CGI:
$Apache::SizeLimit::CHECK_EVERY_N_REQUESTS = 2;
This will only check the process size every other time the process size checker is called.
This module is highly platform dependent, please read the CAVEATS section.
This module was written in response to questions on the mod_perl mailing list on how to tell the httpd process to exit if it gets too big.
Actually there are two big reasons your httpd children will grow. First, it could have a bug that causes the process to increase in size dramatically, until your system starts swapping. Second, your process just does stuff that requires a lot of memory, and the more different kinds of requests your server handles, the larger the httpd processes grow over time.
This module will not really help you with the first problem. For that you
should probably look into Apache::Resource or some other means of setting a
limit on the data size of your program. BSD-ish systems have setrlimit()
which will croak your memory gobbling processes. However it is a little
violent, terminating your process in mid-request.
This module attempts to solve the second situation where your process slowly grows over time. The idea is to check the memory usage after every request, and if it exceeds a threshold, exit gracefully.
By using this module, you should be able to discontinue using the Apache configuration directive MaxRequestsPerChild, although for some folks, using both in combination does the job. Personally, I just use the technique shown in this module and set my MaxRequestsPerChild value to 6000.
This module is platform dependent, since finding the size of a process is pretty different from OS to OS, and some platforms may not be supported.
Currently supported OSes:
setmax
function), and see if the
CHECK_EVERY_N_REQUESTS
option is of benefit.
NOTE: This is only known to work for solaris 2.6 and above. Evidently the /proc filesystem has changed between 2.5.1 and 2.6. Can anyone confirm or deny?
If your platform is not supported, and if you can tell me how to check for the size of a process under your OS (in KB), then I will add it to the list. The more portable/efficient the solution, the better, of course.
Possibly provide a perl make/install so that the SizeLimit.pm is created at build time with only the code you need on your platform.
If Apache was started in non-forking mode, should hitting the size limit cause the process to exit?
Doug Bagley <doug+modperl@bagley.org>, channeling Procrustes.
Brian Moseley <ix@maz.org>: Solaris 2.6 support
Apache::SizeLimit - Because size does matter. |