On Tue, Oct 22, 2013 at 12:39 PM, David Lang <[email protected]> wrote: > On Tue, 22 Oct 2013, Pavel Levshin wrote: > >> even the load balancing hack works 'well enough' once you accept that you >>> are balancing per batch rather than per message (even if you did balance >>> per message, you really have no idea how expensive a particulare message is >>> going to be, so you are not really balancing the work precisely, you are >>> only doing so statistically, and balancing per batch rather than per >>> message is just as valid statistically) >>> >> >> No, it will not work in general. Suppose you have a batch of 256 and 8 >> actions to select. 256 divides by 8, so you will put all you load on just >> one server. Selecting "right" numbers is hard. >> > > actualy it will, you see 256 is the max batch size, rsyslog will grab > _up_to_ 256 messages for the batch, so if you incrament per message you > will seldom be incrimenting by 256 (unless your system is always running > behind) > > but if I am understanding things correctly, putting set $/counter = > $/counter +1; in your config will end up incrimenting counter by 1 per > batch, not by the number of messages in the batch, with the race condition > that two different threads may end up racing and ending up with $/counter > only going up by 1 when it should go up by 2. > > No! See why I say it's very unintuitive? ;)
It count's *every* message, but does so a) in one loop b) before advancing to the next action so if you have (pseudo-code) 1. set $/glob = $/glob +1; 2. action write $/glob and 4 messages a,b,c,d, this will happen. All loops are unrolled in the pseudo-execution: set $glob = 1 set $glob = 2 set $glob = 3 set $glob = 4 write 4 write 4 write 4 write 4 Again, IMHO this is *extremely far* from what you expect. I really doubt that load-balancing based on this counter will work really well, even stastitcally over a longer period. Rainer _______________________________________________ rsyslog mailing list http://lists.adiscon.net/mailman/listinfo/rsyslog http://www.rsyslog.com/professional-services/ What's up with rsyslog? Follow https://twitter.com/rgerhards NOTE WELL: This is a PUBLIC mailing list, posts are ARCHIVED by a myriad of sites beyond our control. PLEASE UNSUBSCRIBE and DO NOT POST if you DON'T LIKE THAT.
