Do not launch a shell for each check

[Thomas Guyot-Sionnest]

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On 10-06-01 05:21 AM, Andreas Ericsson wrote:
> On 05/31/2010 04:28 PM, Matthieu Kermagoret wrote:
>> Hi list,
>>
> 
> Hi Matt :)
> 
>> I'd like to propose a performance patch for Nagios that reduces the
>> number of Nagios' descendant processes.
>>
> 
> Thanks. The idea behind the patch is good. The patch itself is not so
> stellar though.
> 
> First off, the way you're building the command is far from optimal.
> So far from it that it's quite easy to construct a command-line
> that yields worse performance with your patch than forking a new
> shell to take care of the command to run. A better approach is to
> malloc() once and make sure the resulting buffer is large enough to
> hold the resulting command-line and iterate over it once using a
> simple "while (*p)" loop, discarding backslashes and handling quoting
> as you go.
> 
> Secondly, it would be a lot better if the parse_command_line() function
> automagically detects special shell characters (pipes, stdio/stdin/stderr
> redirection, job-control stuff etc etc) and automagically used the shell
> to run such commands. That would, barring bugs, make it possible to use
> your patch with all existing Nagios configs without modifying those
> configurations. Considering the fact that the standard notification
> command includes a pipe, that's a pretty important thing to remember.
> 
> Thirdly, you define the macro WHITESPACES in two different locations,
> which is error-prone.
> 
> Fourthly, the parse_command_line() function is, with this patch, only
> used from base/checks.c, so it would be much better off residing in
> that file, and scoped within that file only. I realize it could quite
> easily be used at more places later, but then a separate patch moving
> it out to global scope would be a lot better, since those patches may
> not be accepted.

Hey, I had that idea for quite some time but never got around
implementing it. Thanks guys for getting to it ;)

So if I may add something, my idea was to use a different command syntax
using ! characters to separate arguments. for ex:

command_exec \
$USER1/check_ping!-H!$HOSTADDRESS$!-w!$ARG1$!-c!$ARG2$!-p!1!-t!1

the ability to escape ! and \ would be useful too, and I think it would
make it much simpler to code and use than any other "smart" method.

The same could be done to nrpe, and this would allow a safe way to pass
command arguments!

Just my .2 cents...

- -- 
Thomas
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