HashedWheelTimer is a good design of Timer for Dubbo to use, thank yuhang~
> 在 2019年1月25日，上午10:33，yuhang xiu <[email protected]> 写道： > > Yesterday I received a reply from the netty community: > > just because we usually want to be on the same thread as the EventLoop of >> the Channel. that said there is nothing wrong about the HashedWheelTimer. > > > It seems that netty does not use HashedWheelTimer not because of its own > problems. > > I think we can safely continue to use HashedWheelTimer. However, we still > need to pay attention to the fact that if there is a large delay in the > task, we need to use or even give up using HashedWheelTimer, and the task > that seems to be blocked is not suitable. > > Thx for jingfeng's question. Very valuable. > :) > > Jason Joo <[email protected]> 于2019年1月24日周四 上午10:44写道： > >> hi, moe >> >> This is the main differences: >> >> ScheduledThreadPoolExecutor >> >> O(log N) for adding new task >> O(1) per each timer tick (but tick per each task, so N overall) >> O(log N) cancelling the task >> lock per each tick/task >> HashedWheelTimer >> >> O(1) adding new task >> O(m) per each timer tick (m ~ N/C where C > 512 approx), so ~C ticks >> overall >> O(m) for cancelling a task >> lock per bucket of tasks (on each tick) >> >> >> best regards, >> >> Jason >> >>> On Jan 24, 2019, at 10:09, 徐靖峰 <[email protected]> wrote: >>> >>> Hi, Jason，a nice opinion. >>> >>> I have noticed that this issue[1] in Github encourage the change from >> Schedule to HashedWheelTimer, but didn’t give a vert detailed reason. >>> >>> Is HashedWheelTimer really an unquestionable choice? >>> >>> [1] https://github.com/apache/incubator-dubbo/issues/1371 < >> https://github.com/apache/incubator-dubbo/issues/1371> >>> >>>> 在 2019年1月24日，上午9:53，Jason Joo <[email protected]> 写道： >>>> >>>> Maybe because the main scenario dubbo faces is persistent connection. >>>> For persistent connections the most frequent thing is ticking. >>>> >>>> ScheduledThreadPoolExecutor is O(1)*connections compared to O(C) in >> HashedWheelTimer when ticking. >>>> Considering connections is far less then C ScheduledThreadPoolExecutor >> maybe more efficient in my opinion. >>>> >>>> best regards, >>>> >>>> Jason >>> >> >>
