Hi,
So this is not correct: > and > the Bolt creates a task for processing each incoming Tuple. Storm create exactly *BoltTaskParallelism* tasks and assigns incoming messages to tasks (according to the used connection pattern -- shuffle, fieldsGrouping etc). Futhermore: > If there > are not enough tasks, then the excess Tuples are made to wait in a > queue of the executor. No. There is no thing as "not enough tasks". Each task has its own input queue/buffer and tuple are stored there. The executor threads process one or multiple tasks. Thus, if a task is currently "on hold", new tuples are just added to the task's input queue. If an executor picks up on of its tasks for processing, the buffered tuples of the task are processed. -Matthias On 05/16/2016 09:07 AM, Adrien Carreira wrote: > +1 > > 2016-05-16 6:40 GMT+02:00 Navin Ipe <[email protected] > <mailto:[email protected]>>: > > Hi, > > I've seen the explanations > > <http://www.michael-noll.com/blog/2012/10/16/understanding-the-parallelism-of-a-storm-topology/>, > but none of them explain it in terms of what I see in the code. This > is what I understood: > > int BoltParallelism = 3; > int BoltTaskParallelism = 2; > builder.setBolt("bolt1", new BoltA(), *BoltParallelism*) > .setNumTasks(*BoltTaskParallelism*) > > BoltParallelism creates 3 instances of BoltA. These are the executors. > BoltTaskParallelism allows Tuples to come into BoltA very fast, and > the Bolt creates a task for processing each incoming Tuple. If there > are not enough tasks, then the excess Tuples are made to wait in a > queue of the executor. > > Strange thing is that the explanation says the tasks are run in a > single thread, so obviously I misunderstood something. Could you > help me understand it? > > -- > Regards, > Navin > >
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