Problem extending the "Status Information" size.

[Ethan Galstad]

ncolin at technodiva.com wrote:
> Hi,
> 
> I need to enter informations in "passive check" services via the FIFO
> (command file).
> 
> The problem is : The size of the buffer used to store Status Informations is
> too small (332 bytes). The datas are truncated.
> 
> I found the #define value ( include/objects.h : MAX_PLUGINOUTPUT_LENGTH )
> and extend it to 10240 but the datas are still truncated ( around 1024 bytes
> ).
> 
> I found another #define for the size of a buffer used to store the complete
> input string ( include/common.h : MAX_INPUT_BUFFER ) which is set to 1024.
> But extending its value does not seem enough : Now, I can not update the
> passive check services.
> 
> So, does someone know how to increase the "Status Information" size ? Which
> define do I need to change ? Which part of the code do I need to change ?
> 
> Thanks.
> 
> --
> Nicolas COLIN.
> 

The problem you'll run into is due to a limitation with FIFOs in 
general.  The POSIX standard only guarantees an atomic write of 512 
bytes max to a FIFO, so writing more data than 512 bytes at a time could 
land you in trouble.  AFAIK, most OSes bump this level up a bit, but the 
max buffer size on a FIFO is often limited to 4K, so your total write 
size can't really be above that level.

Length limitations for plugin output will disappear with Nagios 3.x. 
There is a new IPC method for handling active host/service checks that 
allows for long plugin output (its capped at 4K for safety's sake) and 
there is a new external command that will allow passive checks to have 
longer (and multiline) output as well.  The new PROCESS_EXTERNAL_FILE 
command will tell Nagios to read other external commands/passive checks 
results from an external (flat) file.  Regular files don't have line 
length limitations, so this will be a useable workaround.

So, your the problem you have will disappear once Nagios 3 is released, 
but it will still be a problem for Nagios 1/2.  :-(  Hope that helps.


Ethan Galstad,
Nagios Developer
---
Email: nagios at nagios.org
Website: http://www.nagios.org

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