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From Andra Lungu <lungu.an...@gmail.com>
Subject Re: Monitoring a Flink Job
Date Mon, 29 Jun 2015 20:36:07 GMT
Caution! I am getting philosophical. Stop me if I'm talking nonsense!

You are suggesting a list that will have one or two entries per vertex =
(approx) billions. Won't this over-saturate my memory? I am already filling
it with lots of junk resulted from the computation...

On Mon, Jun 29, 2015 at 1:58 PM, Fabian Hueske <fhueske@gmail.com> wrote:

> Have you tried to use a custom accumulator that just appends to a list?
>
> 2015-06-29 12:59 GMT+02:00 Andra Lungu <lungu.andra@gmail.com>:
>
> > Hey Fabian,
> >
> > I am aware of the way open, preSuperstep(), postSuperstep() etc can help
> me
> > within an interation, unfortunately I am writing my own method here. I
> > could try to briefly describe it:
> >
> > public static final class PropagateNeighborValues implements
> > NeighborsFunctionWithVertexValue(...) {
> >     @Override
> >     public void iterateNeighbors(Iterable..., Collector...) {
> >              while(iterator.hasNext) neighbors++;
> >              // and I would need something like
> >              appendToFile(myAwesomeFile, neighbors);
> >     }
> > }
> >
> > Open() and synchronised are definitely not doing the trick for me right
> > now.
> > Any other way !? :(
> >
> > On Mon, Jun 29, 2015 at 11:36 AM, Fabian Hueske <fhueske@gmail.com>
> wrote:
> >
> > > You can measure the time of each iteration in the open() methods
> > operators
> > > within an iteration. open() will be called before each iteration.
> > > The times can be collected by either printing to std out (you need to
> > > collect the files then...) or by implementing a list accumulator. Each
> > time
> > > should include the iteration# und parallel task id.
> > > After the execution, the acculuator will be available in the execution
> > > result.
> > >
> > > Accumulators can of course also be used to collect number of messages,
> > etc.
> > >
> > > Best, Fabian
> > >
> > > 2015-06-29 9:55 GMT+02:00 Flavio Pompermaier <pompermaier@okkam.it>:
> > >
> > > > Why don't you use Flink dataset output functions (like writeAsText,
> > > > writeAsCsv, etc..)?
> > > > Or if they are not sufficient you can implement/override your own
> > > > InputFormat.
> > > >
> > > > From what is my experience static variables are evil in distributed
> > > > environments..
> > > > Moreover, one of the main strengths of Flink are its input/output
> APIs
> > > so I
> > > > would avoid to write to a file in that way.
> > > >
> > > > Of course, dataset.append() will be a very convenient API to add
> > (IMHO).
> > > >
> > > > Best,
> > > > Flavio
> > > >
> > > >
> > > > On Sat, Jun 27, 2015 at 4:19 PM, Andra Lungu <lungu.andra@gmail.com>
> > > > wrote:
> > > >
> > > > > Hey guys,
> > > > >
> > > > > Me again :) So now that my wonderful job finishes, I would like to
> > > > monitor
> > > > > it a bit (i.e. build some charts on the number of messages per
> > vertex,
> > > > > compute the total amount of time elapsed per computation per
> vertex,
> > > > etc).
> > > > >
> > > > > The main computational-intensive operation is a coGroup. There,
> > within
> > > > the
> > > > > iteration I count the number of "messages" sent and then I do
> simple:
> > > > >
> > > > > Files.append(messages, messagesTempFile, Charsets.UTF_8);
> > > > >
> > > > > The problem is that with this approach, I get a deadlock (yes!! Now
> > > that
> > > > I
> > > > > know the code itself works I am positive that the deadlock comes
> from
> > > the
> > > > > append -this regarding my previous mail-). It is normal if you come
> > to
> > > > > think of it 200 something threads are trying to write to the same
> > > file...
> > > > >
> > > > > A possible workaround is this one:
> > > > >
> > > > > public class Singleton {
> > > > >     private static final Singleton inst= new Singleton();
> > > > >
> > > > >     private Singleton() {
> > > > >         super();
> > > > >     }
> > > > >
> > > > >     public synchronized void writeToFile(String str) {
> > > > >         // Do whatever
> > > > >     }
> > > > >
> > > > >     public Singleton getInstance() {
> > > > >         return inst;
> > > > >     }
> > > > > }
> > > > >
> > > > > Singleton.getInstance().writeToFile("Hello!!");
> > > > >
> > > > > However, I am not sure how well Flink plays with synchronised....
> > > > >
> > > > > Is there a smarter way to do it?
> > > > >
> > > > > Thanks!
> > > > >
> > > > > Andra
> > > > >
> > > >
> > >
> >
>

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