On Fri, May 3, 2013 at 11:19 AM, David Lang <[email protected]> wrote: > On Fri, 3 May 2013, David Lang wrote: > > On Fri, 3 May 2013, Rainer Gerhards wrote: >> >> tracking state between messages will require a major set of changes to >>>> rsyslog internals (think of of problems like having multiple threads >>>> processing messages and the need for them to start sharing state >>>> information (potentially a LOT of state information) >>>> >>>> Let me jump on that one (waited for the discussion). I think global >>> variables are not that hard, I just did not do them as I questioned if >>> there is any use case. In essence it just needs to have some separate >>> namespace. >>> >>> Do you see use cases where this would make sense? >>> >> >> Setting variables that get used for other messages sounds useful, I can >> think of several ways to use this (a simple one would be to tag if messages >> happen during business hours or not, triggered by special log messages. >> >> My main concern is around the locking needed to update such global >> variables when there are lots of threads (and lots of global variables) >> around. Since we are talking about variable length strings there is no way >> to do atomic updates, so you will need to have reader and writer locks or >> some form of rcu to manage the updates. Just the overhead of grabbing and >> releasing the read lock for each message is enough overhead to be worried >> about, even when no updates happen. >> >> Now, as always, I may be missing some trick that eliminates this worry, >> if so I'd love to hear about it. >> > > A secondary concern I have is the misunderstandings that will arise around > the use of global variables. Given that various things can cause logs to be > re-ordered (network issues, queuing issues, thread scheduling, relay > delays, etc), expectations that you can see one log before another and rely > on global variables being set for the first one before the second is > processed will usually, but not always work. > It's definitely not a replacement for SEC...
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.
