Re: [PHP-INSTALL] Questions regarding limits of processes launched by system, exec, passthru ...

[email protected] (Keith Roberts) Thu, 25 Sep 2008 12:31:42 +0100 (BST)
Newsgroups	php.install
Message-ID	<[email protected]>
On Thu, 25 Sep 2008, Valentin Schmid - ICSurselva AG wrote:

> To: [email protected]
> From: Valentin Schmid - ICSurselva AG <[email protected]>
> Subject: [PHP-INSTALL] Questions regarding limits of processes launched by
>     system, exec, passthru ...
> 
> Hello all,
>
> Is there a way to limit the memory consumption and / or the CPU
> consumption of processes launched by the php functions system,
> exec, passthru, proc_open and shell_exec?
>
> We use mod_php with an apache (mpm-prefork) on Linux.
>
> The following settings don't have any effect at all:
> PHP:
>  max_execution_time 30
>  memory_limit 8M
> Apache:
>  RLimitCPU 30 30
>  RLimitMEM 8388608 8388608
>
> The limits above do have effect on php-scripts (without system calls)
> and on CGIs (as well on processes launched by CGIs).
>
> Any Ideas?
>
> Kind Regards
> valli
>
>
> PS: I tested it with the following two scripts:
> system_memorytest.php
> =====================
> <html>
> <head>
>  <title>php-systemcall-memory test</title>
> </head>
> <body>
>  php-systemcall-memory test<br>
>  ... and here's the system call:<br>
>  <pre>
> <?php
>   $cmd = '/usr/bin/perl -e \'
>      $| = 1;
>      print "start of the systemcall<br>\n";
>      $s = "teststr_";
>      while (1) {
>         print "len=".length($s)."<br>\n";
>         sleep(1);
>         $s .= $s;
>      }
>   \'';
>   print htmlspecialchars($cmd);
> ?>
>  </pre>
> <?php
>  ob_flush();
>  flush();
>  system($cmd);
> ?>
> </body>
> </html>
>
>
> system_timeouttest.php
> ======================
> <html>
> <head>
>  <title>php-systemcall-timeout test</title>
> </head>
> <body>
>  php-systemcall-timeout test<br>
>  ... and here's the system call:<br>
>  <pre>
> <?php
>   $cmd = '/usr/bin/perl -e \'
>      $| = 1;
>      print "start of the systemcall<br>\n";
>      $i = 0;
>      while (1) {
>         if (($i % 10000000) == 0) {
>            print "i=".$i."<br>\n";
>         }
>         $i += 1;
>      }
>   \'';
>   print htmlspecialchars($cmd);
> ?>
>  </pre>
> <?php
>  ob_flush();
>  flush();
>  system($cmd);
> ?>
> </body>
> </html>
>

What OS are you running? If it's Unix/Linux then you might 
be able to control these settings with ulimit.

Please see the manual page for ulimit for details.

'pinfo' is a lynx-style info page browser that I find 
very usefull for browsing info manual pages on Linux.

from the Linux info pages for ulimit:

Here is a list of resources for which you can specify a 
limit. Memory and file sizes are measured in bytes.

`RLIMIT_CPU'
The maximum amount of CPU time the process can use.  If it 
runs for longer than this, it gets a signal: `SIGXCPU'. 
The value is measured in seconds.  *Note Operation Error 
Signals::.

`RLIMIT_FSIZE'
The maximum size of file the process can create. Trying to 
write a larger file causes a signal: `SIGXFSZ'.  *Note 
Operation Error Signals::.

`RLIMIT_DATA'
The maximum size of data memory for the process.  If the 
process tries to allocate data memory beyond this amount, 
the allocation function fails.

`RLIMIT_STACK'
The maximum stack size for the process.  If the process 
tries to extend its stack past this size, it gets a 
`SIGSEGV' signal. *Note Program Error Signals::.

`RLIMIT_CORE'
The maximum size core file that this process can create. 
If the process terminates and would dump a core file larger 
than this, then no core file is created.  So setting this 
limit to zero prevents core files from ever being created.

`RLIMIT_RSS'
The maximum amount of physical memory that this process 
should get. This parameter is a guide for the system's 
scheduler and memory allocator; the system may give the 
process more memory when there is a surplus.

`RLIMIT_MEMLOCK'
The maximum amount of memory that can be locked into 
physical memory (so it will never be paged out).

`RLIMIT_NPROC'
The maximum number of processes that can be created with the 
same user ID.  If you have reached the limit for your user 
ID, `fork' will fail with `EAGAIN'.  *Note Creating a 
Process::.

`RLIMIT_NOFILE'
`RLIMIT_OFILE'
The maximum number of files that the process can open.  If 
it tries to open more files than this, its open attempt 
fails with `errno' `EMFILE'.  *Note Error Codes::.  Not all 
systems support this limit; GNU does, and 4.4 BSD does.

`RLIMIT_AS'
The maximum size of total memory that this process should 
get. If the process tries to allocate more memory beyond 
this amount with, for example, `brk', `malloc', `mmap' or 
`sbrk', the allocation function fails.

`RLIM_NLIMITS'
The number of different resource limits.  Any valid RESOURCE 
operand must be less than `RLIM_NLIMITS'.

-- Constant: int RLIM_INFINITY
This constant stands for a value of "infinity" when 
supplied as the limit value in `setrlimit'.

`ulimit' and the command symbols are declared in `ulimit.h'.

HTH

Kind Regards,

Keith Roberts

-----------------------------------------------------------------
Websites:
http://www.php-debuggers.net
http://www.karsites.net
http://www.raised-from-the-dead.org.uk

The mind of the prudent is ever getting knowledge, and the
eear of the wise is ever seeking, inquiring for and craving
knowledge. Pr. 18:15 Amp

All email addresses are challenge-response protected with
TMDA [http://tmda.net]
-----------------------------------------------------------------