[Nagiosplug-devel] Perf Data

Subhendu Ghosh sghosh at sghosh.org
Tue Feb 18 17:42:13 UTC 2003

On Tue, 18 Feb 2003, Ethan Galstad wrote:
> There are two pipes of interest.  One is the external command file, 
> which is implemented as a FIFO and is restricted by the PIPE_BUF 
> limit (512 bytes minimum for POSIX).  Passive checks have to deal 
> with this limit, but not active checks.
> The other pipe is used for IPC between the main (parent) Nagios 
> process and the child processes.  Each child writes the results of a 
> plugin check (along with host/service name) to the pipe, at which 
> point the parent reads it and process it.  This pipe is also 
> restricted by the PIPE_BUF limit.  With host/service name overhead, 
> you're left with about 350 bytes useable for plugin output+perfdata.  
> It should be noted that *both* active and passive checks have results 
> sent through this pipe.  Passive checks enter through the FIFO and 
> then get dumped into this pipe.
> If the size of the pipe becomes a real issue, we can probably break 
> with POSIX compliance on most systems.  The POSIX standard states a 
> minimum of 512 bytes, but Linux has a 4K atomic write limit, while 
> Solaris may have an 8K limit (I don't recall offhand).  I guess I'll 
> have to deal with it if and when it comes up.

The second pipe - is that a single pipe per running install from the 
temp_file var in the config file?



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