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From Gyula Fóra <gyula.f...@gmail.com>
Subject Re: Checkpoints keep waiting on source locks
Date Wed, 21 Oct 2015 12:01:39 GMT
Thanks!
I am personally using Thread.sleep() a lot for flow control in my test
topologies, this might only be me, but it seems to be a pretty annoying
thing when you want to test your streaming jobs.

Stephan Ewen <sewen@apache.org> ezt írta (időpont: 2015. okt. 21., Sze,
13:59):

> Hey!
>
> The issue is that checkpoints can only happen in between elements being in
> the pipeline. You block the pipeline in the sleep() call.
> Since the checkpoint lock is not fair, the few cycles that the source
> releases the lock are not enough for the checkpointer to acquire it.
>
> I wonder if this is an artificial corner case, or actually an issue. The
> solution is theoretically simple: Use a fair lock, but we would need to
> break the data sources API and switch from "synchronized(Object)" to a fair
> "java.concurrent.ReentrantLock".
>
> Greetings,
> Stephan
>
>
> On Wed, Oct 21, 2015 at 1:47 PM, Gyula Fóra <gyula.fora@gmail.com> wrote:
>
> > Hey All,
> >
> > I think there is some serious issue with the checkpoints. Running a
> simple
> > program like this won't complete any checkpoints:
> >
> > StreamExecutionEnvironment env =
> > StreamExecutionEnvironment.getExecutionEnvironment();
> > env.setParallelism(2);
> > env.enableCheckpointing(5000);
> >
> > env.generateSequence(1, 100).map(t -> { Thread.sleep(1000); return t; })
> > .map(t -> t).print();
> > env.execute();
> >
> > The job will start executing and triggering checkpoints but the the
> > triggerCheckpoint method of the StreamTask will be stuck waiting for the
> > checkpoint lock. It will never take a snapshot...
> >
> > Any ideas?
> > This happens on any parallelism, and for other sources as well.
> >
> > Cheers,
> > Gyula
> >
>

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