Re: [evlog-dev] evlog and db2

Hi Mark,

There is a little clearer example on how to use the notification APIs under
evlog/user/cmd/evlnotifyd/test

Look at the testclient.c or test.c

evlactiond is also a notification client. You may want to look at the code
too. it is under evlog/user/cmd/evlactiond .

Regarding performance between notification vs plugin, it is depends on what
do you do when you get a signal with notify scheme or a event record with
the plugin.

With notify scheme you will get notify when a match happens (event that you
register to be notified), along with the signal you will get the recid, now
if you decide that  you need more info about the event you could use the
recid and open the log via posix_log_read and some others api to look for
that particular record....

On the other using the plugin method, you probably want to process the
events very quick then write them to the database (you may want to keep the
db connection open all the time, open the db connection with
_evlInitPlugin). If you can process them faster than the rate of arriving
events than you may want to consider the plugin method. If you can't
process them fast enough, you still can buffer them when they arrive then
process them latter. The TCP plugin buffers events when the connection to
the remote host goes away, you may want something similar.

Best regards, Hien.



Hien Nguyen
[email protected]
(503) 578-4347


                                                                                                                                                 
                      Mark Megerian/Rochester/IBM@IBMUS                                                                                          
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                      ceforge.net                              Subject:  [evlog-dev] evlog and db2                                               
                                                                                                                                                 
                                                                                                                                                 
                      03/05/2003 02:18 PM                                                                                                        
                                                                                                                                                 
                                                                                                                                                 




I have made good progress with getting the evlog data into a db2 table.  In
looking through the code in evlview for getting notified of new events, I
was puzzled by something.

I suspect this is a naive question, but:

- The code uses posix_log_notify_add to ask to be notified about new
events, but then it uses posix_log_read to process all of the events.  To
the uninitiated, that seems like a contradiction.  Why ask to be notified,
if you are essentially going to loop on reading the log for new events
anyway?  Is it because there is a level of indirection between the evlog
event, and this posix log??

Also, I am interested in getting any opinions on the performance
expectations of using this notify technique vs. the plug-in technique.
Expecting to have a large volume of events over 1,024 nodes, so pathlength
is important.


thanks!



Mark Megerian    (507) 253-1682
[email protected]




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