Having more tasks than executors is only helpful, if you want to change the parallelism of a spout or bolt during runtime (by using command "storm rebalance"). If you do not want to change parallelism there is no advantage in having more tasks than executors.
-Matthias On 07/30/2015 10:24 AM, 鄢来琼 wrote: > If two task is run in one executor, both tasks are run in serial mode, > not parallel mode. > > > > Tasks in serial mode is faster than parallel mode? > > > > *发件人:*鄢来琼 > *发送时间:*Thursday, July 30, 2015 3:51 PM > *收件人:*'[email protected]' > *主题:*The relation between executor and Task > > > > Hi ALL, > > > > *An */*executor*/* **is a thread that is spawned by a worker process. It > may run one or more tasks for the same component (spout or bolt).* > > *A */*task*/* **performs the actual data processing — each spout or bolt > that you implement in your code executes as many tasks across the > cluster. The number of tasks for a component is always the same > throughout the lifetime of a topology, but the number of executors > (threads) for a component can change over time. This means that the > following condition holds true: *|*#threads ≤ #tasks*|*. By default, the > number of tasks is set to be the same as the number of executors, i.e. > Storm will run one task per thread.* > > http://storm.apache.org/documentation/Understanding-the-parallelism-of-a-Storm-topology.html > > > > According the above, the executor run one or more spout or bolt. > > Could you tell me the life cycle of executor and spout? > > Could you tell me a use case about executor has more than one task. > > When the executor need more than one task? > > > > Thanks a lot. > > > > Regards, > > > > Peter > > >
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