-----------
Installing
-----------

After installing PNP using:

configure
make all
make install

you should find a new binary in your 

	/path/to/nagios/bin/ 

directory called "npcd".

This is the new Nagios Performancedata C Daemon (npcd).

The idea was to reduce service check latency which were mentioned 
on bigger installations when calling process_perfdata.pl in 
standard mode (nagios executes a perfdata_command).

--------------------
Theory of Operation
--------------------

Instead of forking a new child to execute the process_perfdata 
command (process_perfdata.pl) Nagios will write service perfdata 
to a file (built-in function) and rotate this file every x seconds 
to a spool directory.

npcd reads out the files in that spool directory in alphabetical order 
and starts up process_perfdata.pl (bulk mode) with multiple threads 
(using linux pthread library).

On the other side process_perfdata.pl gets the filename to process, 
opens it, reads it line by line and creates/updates the RRDFiles in 
the usual way.

---------------------
Changes to nagios.cfg
---------------------

This is just a configuration example.

#nagios.cfg

   service_perfdata_file=/usr/local/nagios/var/service-perfdata

   service_perfdata_file_template=DATATYPE::SERVICEPERFDATA\tTIMET::$TIMET$\tHOSTNAME::$HOSTNAME$\tSERVICEDESC::$SERVICEDESC$\tSERVICEPERFDATA::$SERVICEPERFDATA$\tSERVICECHECKCOMMAND::$SERVICECHECKCOMMAND$\tHOSTSTATE::$HOSTSTATE$\tHOSTSTATETYPE::$HOSTSTATETYPE$\tSERVICESTATE::$SERVICESTATE$\tSERVICESTATETYPE::$SERVICESTATETYPE$

   service_perfdata_file_mode=a

   service_perfdata_file_processing_interval=30

   service_perfdata_file_processing_command=process-service-perfdata-file


#commands.cfg

   define command{
        command_name    process-service-perfdata-file
        command_line    /bin/mv /usr/local/nagios/var/service-perfdata /usr/local/nagios/var/perfspool/service-perfdata-$TIMET$
   }

-----------------------------------------
Why working with files instead of a pipe?
-----------------------------------------

In case of a dying daemon there might be complications when working
with pipes. Pipes might fill up when there's no reader resulting 
in data loss.

In case of a hanging npcd the performance data files were written
continously until the filesystem reaches the end of the road.

-------------------------
What to do if npcd hangs?
-------------------------

_Hint:_

RRDTools does not allow you to update data before the last update
time.

Example: npcd thread 1 updates a RRDFile on timestamp "NOW" it is
not possible to insert data before "NOW" in timeline.

So, if you have to stop npcd or it crashes over night resulting
in a huge amount of performance data files on your filesystem I 
would suggest to start the npcd with the changed config file option

	max_threads=1

to reduce the max threads to a number of one single thread.

This should ensure that your RRDFiles should be updated in 
alphabetical order.