Name check is expensive, agreed, but there isn’t anything else currently.
Ideally the stram engine (considering that it is an engine providing resources
like threads etc) should use a ThreadFactory or a ThreadGroup to create
operator threads so identification and adding functionality is easier.
The idea of checking for the same thread between setup() and emit() won’t work
because the emit() check will have to be in the Sink hierarchy and AFAIK a Sink
object doesn’t have access to the corresponding operator, right? Another more
fundamental problem probably is that these threads don’t have to match. The
emit() for any operator (or rather a Sink related to an operator) is ultimately
triggered by an emitTuple() on the topmost input operator in that path which
happens in that input operator’s thread which doesn’t have to match the thread
calling setup() in the downstream operators, right?
On 8/11/16, 10:59 AM, "Vlad Rozov" <v.ro...@datatorrent.com> wrote:
Name verification is too expensive, it will be sufficient to store
currentThread during setup() and verify that it is the same during emit.
Checks should be supported not only for DefaultOutputPort, so we may
have it implemented in various Sinks.
Vlad
On 8/11/16 10:21, Sanjay Pujare wrote:
> Thinking more about this – all of the “operator” threads are created by
the Stram engine with appropriate names. So we can put checks in the
DefaultOutputPort.emit() or in the various implementations of Sink.put() that
the current-thread is one created by the Stram engine (by verifying the name).
>
> We can even use a special Thread object for operator threads so the above
detection is easier.
>
>
>
> On 8/10/16, 6:11 PM, "Amol Kekre" <a...@datatorrent.com> wrote:
>
> +1 on debug proposal. Even if tuples lands up within the window, it
breaks
> all guarantees. A rerun (after restart from a checkpoint) can have
tuples
> in different windows from this thread. A separate thread simply
exposes
> users to unwarranted risks.
>
> Thks
> Amol
>
>
> On Wed, Aug 10, 2016 at 6:05 PM, Vlad Rozov
<v.ro...@datatorrent.com> wrote:
>
> > Tuples emitted between end and begin windows is only one of
possible
> > behaviors that emitting tuples on a separate from the operator
thread may
> > introduce. It will be good to have both checks in place at
run-time and if
> > checking for the operator thread for every emitted tuple is too
expensive,
> > we may have it enabled only in DEBUG or mode with more checks in
place.
> >
> > Vlad
> >
> >
> > Sanjay just reminded me of my typo -> I meant between end_window
and
> >> start_window :)
> >>
> >> Thks
> >> Amol
> >>
> >> On Wed, Aug 10, 2016 at 2:36 PM, Sanjay Pujare
<san...@datatorrent.com>
> >> wrote:
> >>
> >> If the goal is to do this validation through static analysis of
operator
> >>> code, I guess it is possible but is going to be non-trivial. And
there
> >>> could be false positives and false negatives.
> >>>
> >>> Also I suppose this discussion applies to processor operators
(those
> >>> having both in and out ports) so Ram’s example of
JdbcPollInputOperator
> >>> may
> >>> not be applicable here?
> >>>
> >>> On 8/10/16, 2:04 PM, "Ashwin Chandra Putta"
<ashwinchand...@gmail.com>
> >>> wrote:
> >>>
> >>> In a separate thread I mean.
> >>>
> >>> Regards,
> >>> Ashwin.
> >>>
> >>> On Wed, Aug 10, 2016 at 2:01 PM, Ashwin Chandra Putta <
> >>> ashwinchand...@gmail.com> wrote:
> >>>
> >>> > + dev@apex.apache.org
> >>> > - us...@apex.apache.org
> >>> >
> >>> > This is one of those best practices that we learn by
experience
> >>> during
> >>> > operator development. It will save a lot of time during
operator
> >>> > development if we can catch and throw validation error
when
> >>> someone
> >>> emits
> >>> > tuples in a non separate thread.
> >>> >
> >>> > Regards,
> >>> > Ashwin
> >>> >
> >>> > On Wed, Aug 10, 2016 at 1:57 PM, Munagala Ramanath <
> >>> r...@datatorrent.com>
> >>> > wrote:
> >>> >
> >>> >> For cases where use of a different thread is needed, it
can write
> >>> tuples
> >>> >> to a queue from where the operator thread pulls them --
> >>> >> JdbcPollInputOperator in Malhar has an example.
> >>> >>
> >>> >> Ram
> >>> >>
> >>> >> On Wed, Aug 10, 2016 at 1:50 PM, hsy...@gmail.com <
> >>> hsy...@gmail.com
> >>> >> wrote:
> >>> >>
> >>> >>> Hey Vlad,
> >>> >>>
> >>> >>> Thanks for bringing this up. Is there an easy way to
detect
> >>> unexpected
> >>> >>> use of emit method without hurt the performance. Or at
least if
> >>> we
> >>> can
> >>> >>> detect this in debug mode.
> >>> >>>
> >>> >>> Regards,
> >>> >>> Siyuan
> >>> >>>
> >>> >>> On Wed, Aug 10, 2016 at 11:27 AM, Vlad Rozov <
> >>> v.ro...@datatorrent.com>
> >>> >>> wrote:
> >>> >>>
> >>> >>>> The short answer is no, creating worker thread to emit
tuples
> >>> is
> >>> not
> >>> >>>> supported by Apex and will lead to an undefined
behavior.
> >>> Operators in Apex
> >>> >>>> have strong thread affinity and all interaction with
the
> >>> platform
> >>> must
> >>> >>>> happen on the operator thread.
> >>> >>>>
> >>> >>>> Vlad
> >>> >>>>
> >>> >>>
> >>> >>>
> >>> >>
> >>> >
> >>> >
> >>> > --
> >>> >
> >>> > Regards,
> >>> > Ashwin.
> >>> >
> >>>
> >>>
> >>>
> >>> --
> >>>
> >>> Regards,
> >>> Ashwin.
> >>>
> >>>
> >>>
> >>>
> >>>
> >
>
>
>
