Hello Anil, +1 for the proposed solution. I'd change the method name from *pauseEventDispatchToListener* to something more meaningful and understandable for our users, maybe *startPaused*?, *setManualStart* (as we currently have for the *GatewaySenderFactory*)?, *startWithEventDispatcherPaused*?. Best regards.
On Sat, Aug 17, 2019 at 12:55 AM Anilkumar Gingade <aging...@pivotal.io> wrote: > I have updated the wiki based on Dan's comment. > Changes with api: > > *On "AsyncEventQueueFactory" interface - * > > *AsyncEventQueueFactory pauseEventDispatchToListener(); *// This causes > AEQ to be created with paused state. > > > > > On Fri, Aug 16, 2019 at 4:36 PM Anilkumar Gingade <aging...@pivotal.io> > wrote: > > > Dan, > > > > If you look into the API; the AEQ will be created with the pause state. > > The user (application) has to call resume to dispatch the events. > > > > It will be slightly different from GatewaySender behavior; where > > GatewaySender will be created with run mode and then application has to > > call pause on it. Here in this case AEQ will be created with paused > state. > > > > -Anil. > > > > > > On Fri, Aug 16, 2019 at 4:31 PM Dan Smith <dsm...@pivotal.io> wrote: > > > >> Hi Anil, > >> > >> While I like the idea of matching the API of GatewaySender, I'm not > sure I > >> see how this solves the problem. Is it required of the user to call > pause > >> on the AsyncEventQueue as soon as it is created? How would someone do > that > >> when creating AEQs with xml or cluster configuration? Maybe it would be > >> better to not dispatch any events until we are done creating all > regions? > >> > >> -Dan > >> > >> On Fri, Aug 16, 2019 at 2:31 PM Anilkumar Gingade <aging...@pivotal.io> > >> wrote: > >> > >> > Proposal to support controlling capability with event dispatch to > >> > AsyncEventQueue Listener. > >> > > >> > Wiki proposal page: > >> > > >> > > >> > https://cwiki.apache.org/confluence/display/GEODE/%5BDraft%5D+Controlling+event+dispatch+to+AsyncEventListener > >> > > >> > Here is the details from the wiki page: > >> > *Problem* > >> > > >> > *The Geode system requires AEQs to be configured before regions are > >> > created. If an AEQ listener is operating on a secondary region, this > >> could > >> > cause listener to operate on a region which is not yet created or > fully > >> > initialized (for region with co-located regions) which could result in > >> > missing events or dead-lock scenario between region (co-located > region) > >> > creation threads. This scenario is likely to happen during persistence > >> > recovery; when AEQs are created in the start, the recovered AEQ events > >> are > >> > dispatched immediately, thus invoking the AEQ listeners.* > >> > Anti-Goals > >> > > >> > None > >> > *Solution* > >> > > >> > *The proposed solution is to provide a way to control dispatching AEQ > >> > events to the AEQ Listeners, this could be done by adding "pause" and > >> > "resume" capability to the AEQ, which will allow application to decide > >> when > >> > to dispatch events to the listeners. * > >> > > >> > > >> > *The proposal is similar to existing "pause" and "resume" behavior on > >> the > >> > GatewaySender, on which the AEQ is based on (AEQ implementation is a > >> > wrapper around GatewaySender). * > >> > Changes and Additions to Public Interfaces > >> > > >> > *The proposed APIs are:* > >> > > >> > *On "AsyncEventQueueFactory" interface - * > >> > > >> > *AsyncEventQueue pauseEventDispatchToListener();* > >> > > >> > *On "AsyncEventQueue" interface -* > >> > > >> > *boolean resumeEventDispatchToListener(); **returns true or false if > the > >> > event dispatch is resumed successfully.* > >> > > >> > > >> > *The constraints on the pauseEventDispatchToListener() will remain > >> similar > >> > to as in "GatewaySender.pause()" :* > >> > > >> > "It should be kept in mind that the events will still be getting > queued > >> > into the queue. The scope of this operation is the VM on which it is > >> > invoked. In case the AEQ is parallel, the AEQ will be paused on > >> individual > >> > node where this API is called and the AEQ on other VM's can still > >> dispatch > >> > events. In case the AEQ is not parallel, and the running AEQ on which > >> this > >> > API is invoked is not primary then primary AEQ will still continue > >> > dispatching events." > >> > Performance Impact > >> > > >> > > >> > *This will have similar performance and resource implication as with > the > >> > "GatewaySender.pause()" functionality. If the AEQ is not resumed or > >> kept in > >> > "pause" state for long, it may start consuming the configured memory > and > >> > overflow it into disk and may cause disk full scenario.* > >> > Backwards Compatibility and Upgrade Path > >> > > >> > *Impact with rolling upgrade: * > >> > > >> > *As the api is applicable at individual VM level, there is no message > >> > serialization changes involved. And only applicable to the events > >> getting > >> > dispatched to the listeners on that VM. And the AEQ which are > replicated > >> > (for redundancy) continues to work as before.* > >> > > >> > *Backward compatibility requirements: * > >> > > >> > *None. The AEQs are configured and managed at the server side. There > is > >> no > >> > messaging involved between client/server.* > >> > > >> > *Disk formatting changes:* > >> > > >> > *None.* > >> > > >> > *Deprecation and Application Changes:* > >> > > >> > > >> > *None. If needed, the existing application can be modified to control > >> event > >> > dispatch with AEQ listener.* > >> > Prior Art > >> > > >> > *Without this, the AEQ listeners operating on other regions could > >> > experience missing events or dead lock, if there are co-located > >> regions.* > >> > > >> > *This approach is simple and can take advantage of the existing > >> > functionality that is already supported in GatewaySender on which AEQ > is > >> > based on.* > >> > > >> > > > -- Juan José Ramos Cassella Senior Software Engineer Email: jra...@pivotal.io
