Broker's integration in Bro's main/run loop


  • There's a cost to Broker queues being idle. Whenever Broker gets a chance to process messages, it looks for updates to all connections/message-queues/data-stores. That involves sending synchronous messages between actors, and for empty queues, it just gets back an empty deque object it needs to destroy.

  • Broker queues integrate into Bro's run loop by exposing a file descriptor that's ready when the queue is non-empty. Users have the capability of adding arbitrary numbers of queues at run-time (e.g. they can freely add subscriptions to any amount of logs, events, etc.). Relying on select() may become a bottleneck if someone has hundreds of Broker queues, or could possibly break on some systems if FD_SETSIZE is limited to 1024.

Ideas on how to fix:

  • Improve Bro's main run loop and dedicate an IOSource to each Broker queue (instead of sharing a single IOSource like they do now). There might be several things that could be tweaked in the main run loop, but at a minimum, epoll()/kqueue() could alternatively replace select(). Could also think about using something like libev ( to abstract what particular polling backend is used. Might even be able to use libev's timers to fix how Bro's timers are currently coupled w/ there being an active IOSource consistently driving time forward.

  • Move the draining of Broker queues completely off to their own threads. This maybe is adding a bit too much complexity (Broker/CAF uses threads for queues, then Bro would use more threads just to talk to those other threads...). Since CAF becomes a requirement, it may be simpler to start replacing/allowing some areas of Bro's threading to be done w/ CAF actors. And then if Broker exposed an optional API to talk directly w/ CAF actors, the integration w/ Bro may actually become more straightforward.

And those ideas don't have to be mutually exclusive.




Jon Siwek


Jon Siwek



External issue ID