Duplicates cannot happen because the state of all operators will be
rolled back to the latest checkpoint, in case of failures.
On 14.10.20 06:31, Reuven Lax wrote:
Does this mean that we have to deal with duplicate messages over the
back edge? Or will that not happen, since duplicates mean that we rolled
back a checkpoint.
On Tue, Oct 13, 2020 at 2:59 AM Maximilian Michels <[email protected]
<mailto:[email protected]>> wrote:
There would be ways around the lack of checkpointing in cycles, e.g.
buffer and backloop only after checkpointing is complete, similarly how
we implement @RequiresStableInput in the Flink Runner.
-Max
On 07.10.20 04:05, Reuven Lax wrote:
> It appears that there's a proposal
>
(https://cwiki.apache.org/confluence/display/FLINK/FLIP-16%3A+Loop+Fault+Tolerance
<https://cwiki.apache.org/confluence/display/FLINK/FLIP-16%3A+Loop+Fault+Tolerance>
>
<https://cwiki.apache.org/confluence/display/FLINK/FLIP-16%3A+Loop+Fault+Tolerance
<https://cwiki.apache.org/confluence/display/FLINK/FLIP-16%3A+Loop+Fault+Tolerance>>)
> and an abandoned PR to fix this, but AFAICT this remains a
limitation of
> Flink. If Flink can't guarantee processing of records on back
edges, I
> don't think we can use cycles, as we might otherwise lose the
residuals.
>
> On Tue, Oct 6, 2020 at 6:16 PM Reuven Lax <[email protected]
<mailto:[email protected]>
> <mailto:[email protected] <mailto:[email protected]>>> wrote:
>
> This is what I was thinking of
>
> "Flink currently only provides processing guarantees for jobs
> without iterations. Enabling checkpointing on an iterative job
> causes an exception. In order to force checkpointing on an
iterative
> program the user needs to set a special flag when enabling
> checkpointing:|env.enableCheckpointing(interval,
> CheckpointingMode.EXACTLY_ONCE, force = true)|.
>
> Please note that records in flight in the loop edges (and the
state
> changes associated with them) will be lost during failure."
>
>
>
>
>
>
> On Tue, Oct 6, 2020 at 5:44 PM Boyuan Zhang
<[email protected] <mailto:[email protected]>
> <mailto:[email protected] <mailto:[email protected]>>> wrote:
>
> Hi Reuven,
>
> As Luke mentioned, at least there are some limitations around
> tracking watermark with flink cycles. I'm going to use
State +
> Timer without flink cycle to support self-checkpoint. For
> dynamic split, we can either explore flink cycle approach or
> limit depth approach.
>
> On Tue, Oct 6, 2020 at 5:33 PM Reuven Lax
<[email protected] <mailto:[email protected]>
> <mailto:[email protected] <mailto:[email protected]>>> wrote:
>
> Aren't there some limitations associated with flink
cycles?
> I seem to remember various features that could not be
used.
> I'm assuming that watermarks are not supported across
> cycles, but is there anything else?
>
> On Tue, Oct 6, 2020 at 7:12 AM Maximilian Michels
> <[email protected] <mailto:[email protected]>
<mailto:[email protected] <mailto:[email protected]>>> wrote:
>
> Thanks for starting the conversation. The two
approaches
> both look good
> to me. Probably we want to start with approach #1 for
> all Runners to be
> able to support delaying bundles. Flink supports
cycles
> and thus
> approach #2 would also be applicable and could be
used
> to implement
> dynamic splitting.
>
> -Max
>
> On 05.10.20 23:13, Luke Cwik wrote:
> > Thanks Boyuan, I left a few comments.
> >
> > On Mon, Oct 5, 2020 at 11:12 AM Boyuan Zhang
> <[email protected] <mailto:[email protected]>
<mailto:[email protected] <mailto:[email protected]>>
> > <mailto:[email protected]
<mailto:[email protected]>
> <mailto:[email protected]
<mailto:[email protected]>>>> wrote:
> >
> > Hi team,
> >
> > I'm looking at adding self-checkpoint
support to
> portable Flink
> > runner(BEAM-10940
> >
<https://issues.apache.org/jira/browse/BEAM-10940
<https://issues.apache.org/jira/browse/BEAM-10940>
> <https://issues.apache.org/jira/browse/BEAM-10940
<https://issues.apache.org/jira/browse/BEAM-10940>>>) for
> both batch
> > and streaming. I summarized the problem
that we
> want to solve and
> > proposed 2 potential approaches in this doc
> >
>
<https://docs.google.com/document/d/1372B7HYxtcUYjZOnOM7OBTfSJ4CyFg_gaPD_NUxWClo/edit?usp=sharing <https://docs.google.com/document/d/1372B7HYxtcUYjZOnOM7OBTfSJ4CyFg_gaPD_NUxWClo/edit?usp=sharing> <https://docs.google.com/document/d/1372B7HYxtcUYjZOnOM7OBTfSJ4CyFg_gaPD_NUxWClo/edit?usp=sharing <https://docs.google.com/document/d/1372B7HYxtcUYjZOnOM7OBTfSJ4CyFg_gaPD_NUxWClo/edit?usp=sharing>>>.
> >
> > I want to collect feedback on which
approach is
> preferred and
> > anything that I have not taken into
consideration
> yet but I should.
> > Many thanks to all your help!
> >
> > Boyuan
> >
>
