The document outlines the creation of an event broker module, detailing its purpose, usage instructions, and advice for implementation. It emphasizes the importance of function pointers for callbacks and provides various examples and structures related to event handling. Additionally, it includes recommendations for initial development practices and external resources for further support.

1. Stop being lazy and write
an event broker module already
Dave Josephsen
dave@dbg.com

2. WHY?!
The NEB interface is AWESOME
Interpreted automata is expensive
Especially via global event handlers and/or
performance-data hooks
You're more likely to make something I can use
too!
2012 2

3. How we're going to do this
Function pointers (and YOU)
What is the event broker?
How do we use it?
A few words of advice
Dissect a couple existing plugins
Nagfs
DNX
2012 3

4. Function Pointers are weird, but they make
callbacks possible
Normal Function Declarations
void main() {
int c2f ( int c ) { return (9/5) *c+32; }
int f2c ( int f ) { return (5/9) *(f-32); }
Argument
int convert (int input, int (*fPointer)(int)) {
return fPointer(input);
}
wha??
void Go() {
int result=convert('72',&f2c);
}
Oh.. ok.
}
2012 4

5. What is the event broker?
Event Broker added
Nagios Event loop
(kinda)
2012 5

6. How do we use it?
Write an init function
int nebmodule_init( int flags, char * args, nebmodule * handle)
Subscribe to the events you want
neb_register_callback(STUFF, handle, '1', &myhandler);
Write handler functions for each event you
subscribed to
int myhandler(int neb_event_type, nebstruct_stuff_data *ds)
Write a de-init function
int nebmodule_deinit(int flags, int reason){ return 0 }
2012 6

7. How do we use it? (cont)
include/nebcallbacks.h
NEBCALLBACK_RAW_DATA
NEBCALLBACK_NEB_DATA
NEBCALLBACK_PROCESS_DATA
NEBCALLBACK_TIMED_EVENT_DATA neb_register_callback(NEBCALLBACK_TIMED_EVENT_DATA, handle, '1', &handler);
NEBCALLBACK_LOG_DATA
NEBCALLBACK_SYSTEM_COMMAND_DATA
NEBCALLBACK_EVENT_HANDLER_DATA
NEBCALLBACK_NOTIFICATION_DATA
NEBCALLBACK_SERVICE_CHECK_DATA base/broker.c
NEBCALLBACK_HOST_CHECK_DATA
NEBCALLBACK_COMMENT_DATA /* fill struct with relevant data */
NEBCALLBACK_DOWNTIME_DATA
NEBCALLBACK_FLAPPING_DATA ds.type=type;
NEBCALLBACK_PROGRAM_STATUS_DATA ds.flags=flags;
NEBCALLBACK_HOST_STATUS_DATA ds.attr=attr;
NEBCALLBACK_SERVICE_STATUS_DATA
NEBCALLBACK_ADAPTIVE_PROGRAM_DATA ds.timestamp=get_broker_timestamp(timestamp);
NEBCALLBACK_ADAPTIVE_HOST_DATA
NEBCALLBACK_ADAPTIVE_SERVICE_DATA ds.event_type=event->event_type;
NEBCALLBACK_EXTERNAL_COMMAND_DATA
NEBCALLBACK_AGGREGATED_STATUS_DATA ds.recurring=event->recurring;
NEBCALLBACK_RETENTION_DATA ds.run_time=event->run_time;
NEBCALLBACK_CONTACT_NOTIFICATION_DATA ds.event_data=event->event_data;
NEBCALLBACK_CONTACT_NOTIFICATION_METHOD_DATA
NEBCALLBACK_ACKNOWLEDGEMENT_DATA ds.event_ptr=(void *)event;
NEBCALLBACK_STATE_CHANGE_DATA
NEBCALLBACK_CONTACT_STATUS_DATA /* make callbacks */
NEBCALLBACK_ADAPTIVE_CONTACT_DATA
neb_make_callbacks(NEBCALLBACK_TIMED_EVENT_DATA,(void *)&ds);
include/broker.h
#define NEBTYPE_TIMEDEVENT_ADD
#define NEBTYPE_TIMEDEVENT_REMOVE
#define NEBTYPE_TIMEDEVENT_EXECUTE int handler(int neb_event_type, nebstruct_timed_event_data *ds)
#define NEBTYPE_TIMEDEVENT_DELAY
#define NEBTYPE_TIMEDEVENT_SKIP
#define NEBTYPE_TIMEDEVENT_SLEEP
2012 7

8. How do we use it? (cont)
Everything is a struct
Every struct is globally scoped
The sky is the limit
enumerate/add/remove events from the queue
reconfigure hosts/services post-runtime
export/import data from/to whatever
process check data, inject/delete check results
GO CRAZY!
2012 8

9. Some words of advice
There's a “hello world” module in contrib
Write your thingy as a stand-alone thingy first, and
then convert it to an EH function
Start simple, and then build up
Avoid Threads
(run them in a separate process)
The DNX guys have pre-packaged the headers for
various versions of Nagios (zomgthankyou)
2012 9

10. Nagfs

11. DNX
●External process IPC
●Service check preemption
●Check result injection

12. OK BYE!
http://old.nagios.org/developerinfo/
http://nagios.larsmichelsen.com/event_broker_options/
http://dnx.sourceforge.net/
(and speaking of “buy”...)