By default there are no `_eventlogger` tasks. To have this feature enabled you need to turn it on by setting topology.eventlogger.executors to a positive number. Ackers are on by default, but can be disabled by setting the number of topology.acker.executors to 0. You should respect these when scheduling a topology because if they are supposed to be there and they are not scheduled messages will be sent to them, but they will be lost. In the case of acking all of the tuples will time out. In the case of the event logger the UI will show it working, but nothing will ever come out. Now that is on a per topology basis, not on a per worker basis. These bolts are like any other bolt. They can be in any worker your scheduler wants to put them in. When inserting an acker bolt it is using a keyed grouping connected to just about everything in your topology, so where you place it is not that critical as it is going to be talking to everything. The event logger bolts are similar, but using a fields grouping based off of component id. https://github.com/apache/storm/blob/4c8a986f519cdf3e63bed47e9c4f723e4867267a/storm-client/src/jvm/org/apache/storm/daemon/StormCommon.java#L346-L357 You could try to be smart to try and collocate the component with the logger for it, but honestly this feature slows your topology down so much already it is probably not worth trying to optimize it as it really will only be used when you need to do some serious debugging.
- Bobby On Tuesday, August 1, 2017, 4:44:55 AM CDT, AMir Firouzi <firouz...@gmail.com> wrote: hi guys i'm working on my own scheduler for storm. i wonder what happens if i create a worker process and put some tasks in it(bolt/spout tasks) but no _eventlogger and _acker tasks. what happens? is it a problem? tuples transferred/emitted from within tasks in this worker will be skipped or they just use another _acker or _loggers in other workers? thanks in advance
