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From Pramod Immaneni <pra...@datatorrent.com>
Subject Re: Sequencing of operator calls
Date Tue, 10 Nov 2015 19:01:59 GMT
Is there a unit test covering it? Otherwise can you write one to test the
hypothesis.

On Tue, Nov 10, 2015 at 11:00 AM, Timothy Farkas <tim@datatorrent.com>
wrote:

> That is what it is looking like to me. The task is submitted
> GenericNode#checkpoint line 504, then at the end of the
> GenericNode#checkpoint line 531 checkpointed is called. I am likely missing
> something, just would like to know what :)
>
> Tim
>
> On Tue, Nov 10, 2015 at 10:51 AM, Pramod Immaneni <pramod@datatorrent.com>
> wrote:
>
> > Tim,
> >
> > Are you suggesting that checkpointed is called before the checkpoint is
> > completely persisted in the storage.
> >
> > Thanks
> >
> > On Tue, Nov 10, 2015 at 10:49 AM, Timothy Farkas <tim@datatorrent.com>
> > wrote:
> >
> > > Chetan,
> > >
> > > I do not see the process of reporting the checkpoint to stram,
> receiving
> > > the ack, and then calling checkpointed. The logic I'm seeing in
> > GenericNode
> > > line 484 is that the checkpoint method is called, it spawns another
> > thread
> > > that writes to hdfs, and then checkpointed is immediately called
> > > afterwards. I am missing something, can you give me some pointers so
> > that I
> > > can better understand the flow?
> > >
> > > Tim
> > >
> > > On Tue, Nov 10, 2015 at 10:33 AM, Munagala Ramanath <
> ram@datatorrent.com
> > >
> > > wrote:
> > >
> > > > Chetan's answer provides a good explanation as well as clarifying
> that
> > > > the difference can be more than 1.
> > > >
> > > > Since checkpointing (i.e. "commit notification" as Thomas refers to
> > > > it) is asynchronous, I'm curious
> > > > about whether the window ids in the checkpointed call are guaranteed
> > > > to be sequential or if they could
> > > > be out of order, i.e. can the checkpointed call see window id 101
> > > > before it sees 100 ?
> > > >
> > > > Ram
> > > >
> > > > On Tue, Nov 10, 2015 at 10:27 AM, Bhupesh Chawda
> > > > <bhupesh@datatorrent.com> wrote:
> > > > > Hi Tim,
> > > > > Thanks for the detailed explanation.
> > > > > I understand that the sequence would be
> > > > > beginWindow  (x) -> endWindow (x) -> checkpointed (x)  ->
> beginWindow
> > > > > (x+1)
> > > > >
> > > > > However when I try to print out the window ids in beginWindow,
> > > endWindow
> > > > > and checkpointed calls,  I see x and x-1 respectively.
> > > > > I.e. If the window just before checkpoint is 100, I see that the
> > > > > checkpointed call had window id 99.
> > > > >
> > > > > Note: This is observed in the local mode of Apex.
> > > > >
> > > > > Thanks
> > > > > -Bhupesh
> > > > > On 10-Nov-2015 11:25 pm, "Timothy Farkas" <tim@datatorrent.com>
> > wrote:
> > > > >
> > > > >> Hi Bhupesh,
> > > > >>
> > > > >> The sequencing of checkpoint called in relation to beginWindow
and
> > > > >> endWindow depends on how your APPLICATION_WINDOW_COUNT and
> > > > >> CHECKPOINT_WINDOW_COUNT are configured. If the two WINDOW_COUNTs
> are
> > > not
> > > > >> configured to be the same then it is possible that checkpointed
is
> > > > called
> > > > >> within an application window. So the sequence of events would
be
> > this:
> > > > >>
> > > > >> beginWindow -> checkpointed -> endWindow
> > > > >>
> > > > >> If the APPLICATION_WINDOW_COUNT and CHECKPOINT_WINDOW_COUNT are
> the
> > > same
> > > > >> (default). Then the sequence of calls would be this:
> > > > >>
> > > > >> beginWindow  (100) -> endWindow (100) -> checkpointed (100)
 ->
> > > > beginWindow
> > > > >> (101)
> > > > >>
> > > > >> The numbers in the sequence represent possible streaming window
> Ids
> > > that
> > > > >> each call would be associated with.
> > > > >>
> > > > >> The StateMachine which calls these callbacks for non-input
> operators
> > > is
> > > > in
> > > > >> GenericNode.java.
> > > > >>
> > > > >> Tim
> > > > >>
> > > > >> On Tue, Nov 10, 2015 at 3:36 AM, Bhupesh Chawda <
> > > > bhupesh@datatorrent.com>
> > > > >> wrote:
> > > > >>
> > > > >> > Hi Chetan / Community,
> > > > >> >
> > > > >> > Can someone please elaborate on why the window id supplied
to
> > > > >> > CheckpointListener and the Operator would differ.
> > > > >> > I tried looking at the window ids of checkpointed() and
the
> > > > beginWindow()
> > > > >> > calls and they differ by 1. Don't know why this should be
the
> > case.
> > > > >> >
> > > > >> > Thanks.
> > > > >> > -Bhupesh
> > > > >> >
> > > > >> > On Thu, Sep 17, 2015 at 5:56 AM, Chetan Narsude <
> > > > chetan@datatorrent.com>
> > > > >> > wrote:
> > > > >> >
> > > > >> > > Short answer is yes.
> > > > >> > >
> > > > >> > > All the control tuples are scheduled to be delivered
outside
> of
> > > the
> > > > >> > window.
> > > > >> > > As checkpointed callback is triggered because of CHECKPOINT
> > > control
> > > > >> > tuple,
> > > > >> > > it will happen after endWindow and before the next
> beginWindow.
> > > > >> > >
> > > > >> > > The windowId supplied to CheckpointListener and the
one
> provided
> > > to
> > > > >> > > Operator need not match even though the sequence is
defined.
> So
> > I
> > > am
> > > > >> > > curious how you intend to use this knowledge.
> > > > >> > >
> > > > >> > > --
> > > > >> > > Chetan
> > > > >> > >
> > > > >> > >
> > > > >> > > On Tue, Sep 15, 2015 at 8:31 AM, Thomas Weise <
> > > > thomas@datatorrent.com>
> > > > >> > > wrote:
> > > > >> > >
> > > > >> > > > It has not changed the operator execution model.
State
> > > > serialization
> > > > >> is
> > > > >> > > > still synchronous, write to HDFS is taken out
of the
> operator
> > > > thread.
> > > > >> > > >
> > > > >> > > > On Tue, Sep 15, 2015 at 8:18 AM, Amol Kekre <
> > > amol@datatorrent.com
> > > > >
> > > > >> > > wrote:
> > > > >> > > >
> > > > >> > > > >
> > > > >> > > > > Sent too soon. Has asynchronous checkpointing
changed
> this?
> > > > >> > > > >
> > > > >> > > > > Amol
> > > > >> > > > >
> > > > >> > > > > Sent from my iPhone
> > > > >> > > > >
> > > > >> > > > > > On Sep 15, 2015, at 12:38 AM, Bhupesh
Chawda <
> > > > >> > > bhupesh@datatorrent.com>
> > > > >> > > > > wrote:
> > > > >> > > > > >
> > > > >> > > > > > Hi All,
> > > > >> > > > > >
> > > > >> > > > > > Is it safe to assume that the checkpointed()
and the
> > > > >> beginWindow()
> > > > >> > > > calls
> > > > >> > > > > > are sequenced?
> > > > >> > > > > > In other words, are these calls part
of the same thread
> > and
> > > > may
> > > > >> not
> > > > >> > > run
> > > > >> > > > > in
> > > > >> > > > > > parallel?
> > > > >> > > > > >
> > > > >> > > > > > Thanks.
> > > > >> > > > > >
> > > > >> > > > > > --
> > > > >> > > > > > -Bhupesh
> > > > >> > > > >
> > > > >> > > >
> > > > >> > >
> > > > >> >
> > > > >>
> > > >
> > >
> >
>

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