Hi Radu, timers are fired in order of their time stamps. Multiple timers on the same time are deduplicated.
if you have the following logic: time = 1, processElement(A) -> put A in state keyed to t=1, registerProcTimer(2) time = 1, processElement(B) -> put B in state keyed to t=1, registerProcTimer(2) // deduplicated time = 2, onTimer(2) -> access state with key t=2-1, get A, B time = 2, pocessElement(C) -> put C in state keyed to t=2, registerProcTimer(3) ... You get all calls in the right order. Does that answer you questions? 2017-03-31 11:36 GMT+02:00 Radu Tudoran <radu.tudo...@huawei.com>: > Hi, > > > > Thanks Fabian. But is there also a fixed order that is imposed in their > execution? > > > > I am asking this because it is not enough just to have them executed > atomically. If once you have the processElement() being called and then > onTimer(), and in the next called you have them vice versa, it would mean > that you need additional mechanism to synchronize your logic. Right? > > For example if in the > > process element you do state.update (newValue) > > and in the ontimer you do out.collect(state.getValue()) > > > > than if you have ev1,ev2 and eve3 coming at consecutive times and once the > function are executed processelement and than timer and then in reverse > order your output would be: > > > > time1: (processElement) ev1 –arrives > state=ev1 > > time2: (processElement – executed first) ev2-arrives state=ev2 > onTime(executed second): out = ev2 > > time3: (processElement – executed second) ev3-arrives state=ev3 > onTime(executed first): out = ev2 > > > > Best regards, > > > > Dr. Radu Tudoran > > Senior Research Engineer - Big Data Expert > > IT R&D Division > > > > [image: cid:image007.jpg@01CD52EB.AD060EE0] > > HUAWEI TECHNOLOGIES Duesseldorf GmbH > > German Research Center > > Munich Office > > Riesstrasse 25, 80992 München > > > > E-mail: *radu.tudo...@huawei.com <radu.tudo...@huawei.com>* > > Mobile: +49 15209084330 <+49%201520%209084330> > > Telephone: +49 891588344173 <+49%2089%201588344173> > > > > HUAWEI TECHNOLOGIES Duesseldorf GmbH > Hansaallee 205, 40549 Düsseldorf, Germany, www.huawei.com > Registered Office: Düsseldorf, Register Court Düsseldorf, HRB 56063, > Managing Director: Bo PENG, Qiuen Peng, Shengli Wang > Sitz der Gesellschaft: Düsseldorf, Amtsgericht Düsseldorf, HRB 56063, > Geschäftsführer: Bo PENG, Qiuen Peng, Shengli Wang > > This e-mail and its attachments contain confidential information from > HUAWEI, which is intended only for the person or entity whose address is > listed above. Any use of the information contained herein in any way > (including, but not limited to, total or partial disclosure, reproduction, > or dissemination) by persons other than the intended recipient(s) is > prohibited. If you receive this e-mail in error, please notify the sender > by phone or email immediately and delete it! > > > > *From:* Fabian Hueske [mailto:fhue...@gmail.com] > *Sent:* Friday, March 31, 2017 11:05 AM > *To:* Radu Tudoran > *Cc:* user@flink.apache.org > *Subject:* Re: concurrency? > > > > Hi Radu, > > the processElement() and onTimer() calls are synchronized by a lock, i.e., > they won't be called at the same time. > > Best, Fabian > > > > 2017-03-31 9:34 GMT+02:00 Radu Tudoran <radu.tudo...@huawei.com>: > > Hi, > > > > I would like to use a processFunction to accumulate elements. Therefore in > the processElement function I will accumulate this element into a state. > However, I would like to emit the output only 1ms later. Therefore I would > register a timer to trigger one second later and read the state and emit it. > > However, I am curious of what happens if in the next ms another event > arrives. In principle both the processElement function and the onTimer > function should be triggered in the same time. My question is: is there a > fix order to execute them? Because if any of them work just like normal > threads, than concurrency related issues could happen when accessing the > state. > > > > >
