I was on the fence between the various overloading methods myself, liking
`start(...)` the least.
Initially, I thought we were interested in offering the ability to call the
reporter out of band, outside `put`.
But after your replies I understand you don't think that's the case, and I
also agree that keeping the reporter in `put(...)` makes the intended use
case more clear.
In most cases it won't even require storing it as a member variable in the
task class.
So, I'm also happy with
`public abstract void put(Collection<SinkRecord> records, BiFunction<...>
failedRecordReporter)`
Konstantine
On Fri, May 15, 2020 at 9:10 AM Randall Hauch <rha...@gmail.com> wrote:
> Konstantine said:
>
> > I notice Randall also used BiFunction in his example, I wonder if it's
> for
> > similar reasons.
> >
>
> Nope. Just a typo on my part.
>
> There appear to be three outstanding questions.
>
> First, Konstantine suggested calling this "failedRecordReporter". I think
> this is minor, but using this new name may be a bit more precise and I'd be
> fine with this.
>
> Second, should the reporter method be synchronous? I think the two options
> are:
>
> 2a. Use `BiConsumer<SinkRecord, Throwable>` that returns nothing and blocks
> (at this time).
> 2b. Use `BiFunction<SinkRecord, Throwable, Future<Void>>` that returns a
> future that the user can optionally use to be synchronous.
>
> I do agree with Konstantine that option 2b gives us more room for future
> semantic changes, and since the producer write is already asynchronous this
> should be straightforward to implement. I think the concern here is that if
> the sink task does not *use* the future to make this synchronous, it is
> very possible that the error records could be written out of order (due to
> retries). But this won't be an issue if the implementation uses
> `max.in.flight.requests.per.connection=1` for writing the error records.
> It's a little less clear, but honestly IMO passing the reporter in the
> `put(...)` method helps make this lambda easier to understand, for some
> strange reason. So unless there are good reasons to avoid this, I'd be in
> favor of 2b and returning a Future.
>
> Third, how do we pass the reporter lambda / method reference to the task?
> My proposal to pass the reporter via an overload `put(...)` still is the
> most attractive to me, for several reasons:
>
> 3a. There's no need to pass the reporter separately *and* to describe the
> changes in method call ordering.
> 3b. As mentioned above, for some reason passing it via `put(...)` makes the
> intent more clear that it be used when processing the SinkRecord, and that
> it shouldn't be used in `start(...)`, `preCommit(...)`,
> `onPartitionsAssigned(...)`, or any of the other task methods. As Andrew
> pointed out earlier, *describing* this in the KIP and in JavaDoc will be
> tough to be exact yet succinct.
> 3c. There is already precedence for evolving
> `SourceTask.commitRecord(...)`, and the pattern is identical.
> 3d. Backward compatibility is easy to understand, and at the same time it's
> pretty easy to describe what implementations that want to take advantage of
> this feature should do.
> 3e. Minimal changes to the interface: we're just *adding* one default
> method that calls the existing method and deprecating the existing
> `put(...)`.
> 3f. Deprecating the existing `put(...)` makes it more clear in a
> programmatic sense that new sink implementations should use the reporter,
> and that we recommend old sinks evolve to use it.
>
> Some of these benefits apply to some of the other suggestions, but I think
> none of the other suggestions have all of these benefits. For example,
> overloading `initialize(...)` is more difficult since most sink connectors
> don't override it and therefore would be less subject to deprecations
> warnings. Overloading `start(...)` is less attractive. Adding a method IMO
> shares the fewest of these benefits.
>
> The one disadvantage of this approach is that sink task implementations
> can't rely upon the reporter upon startup. IMO that's an acceptable
> tradeoff to get the cleaner and more explicit API, especially if the API
> contract is that Connect will pass the same reporter instance to each call
> to `put(...)` on a single task instance.
>
> Best regards,
>
> Randall
>
> On Fri, May 15, 2020 at 6:59 AM Andrew Schofield <
> andrew_schofi...@live.com>
> wrote:
>
> > Hi,
> > Randall's suggestion is really good. I think it gives the flexibility
> > required and also
> > keeps the interface the right way round.
> >
> > Thanks,
> > Andrew Schofield
> >
> > On 15/05/2020, 02:07, "Aakash Shah" <as...@confluent.io> wrote:
> >
> > > Hi Randall,
> > >
> > > Thanks for the feedback.
> > >
> > > 1. This is a great suggestion, but I find that adding an overloaded
> > > put(...) which essentially deprecates the old put(...) to only be used
> > when
> > > a connector is deployed on older versions of Connect adds enough of a
> > > complication that could cause connectors to break if the old put(...)
> > > doesn't correctly invoke the overloaded put(...); either that, or it
> will
> > > add duplication of functionality across the two put(...) methods. I
> think
> > > the older method simplifies things with the idea that a DLQ/error
> > reporter
> > > will or will not be passed into the method depending on the version of
> > AK.
> > > However, I also understand the aesthetic advantage of this method vs
> the
> > > setter method, so I am okay with going in this direction if others
> agree
> > > with adding the overloaded put(...).
> > >
> > > 2. Yes, your assumption is correct. Yes, we can remove the "Order of
> > > Operations" if we go with the overloaded put(...) direction.
> > >
> > > 3. Great point, I will remove them from the KIP.
> > >
> > > 4. Yeah, accept(...) will be synchronous. I will change it to be
> clearer,
> > > thanks.
> > >
> > > 5. This KIP will use existing metrics as well introduce new metrics. I
> > will
> > > update this section to fully specify the metrics.
> > >
> > > Please let me know what you think.
> > >
> > > Thanks,
> > > Aakash
> > >
> > > On Thu, May 14, 2020 at 3:52 PM Randall Hauch <rha...@gmail.com>
> wrote:
> > >
> > > > Hi, Aakash.
> > > >
> > > > Thanks for the KIP. Connect does need an improved ability for sink
> > > > connectors to report individual records as being problematic, and
> this
> > > > integrates nicely with the existing DLQ feature.
> > > >
> > > > I also appreciate the desire to maintain compatibility so that
> > connectors
> > > > can take advantage of this feature when deployed in a runtime that
> > supports
> > > > this feature, but can safely and easily do without the feature when
> > > > deployed to an older runtime. But I do understand Andrew's concern
> > about
> > > > the aesthetics. Have you considered overloading the `put(...)` method
> > and
> > > > adding the `reporter` as a second parameter? Essentially it would add
> > the
> > > > one method (with proper JavaDoc) to `SinkTask` only:
> > > >
> > > > ```
> > > > public void put(Collection<SinkRecord> records,
> > BiFunction<SinkRecord,
> > > > Throwable> reporter) {
> > > > put(records);
> > > > }
> > > > ```
> > > > and the WorkerSinkTask would be changed to call `put(Collection,
> > > > BiFunction)` instead.
> > > >
> > > > Sink connector implementations that don't do anything different can
> > still
> > > > override `put(Collection)`, and it still works as before. Developers
> > that
> > > > want to change their sink connector implementations to support this
> new
> > > > feature would do the following, which would work in older and newer
> > Connect
> > > > runtimes:
> > > > ```
> > > > public void put(Collection<SinkRecord> records) {
> > > > put(records, null);
> > > > }
> > > > public void put(Collection<SinkRecord> records,
> > BiFunction<SinkRecord,
> > > > Throwable> reporter) {
> > > > // the normal `put(Collection)` logic goes here, but can
> > optionally
> > > > use `reporter` if non-null
> > > > }
> > > > ```
> > > >
> > > > I think this has all the same benefits of the current KIP, but
> > > > it's noticeably simpler and hopefully more aesthetically pleasing.
> > > >
> > > > As for Andrew's second concern about "the task can send errant
> records
> > to
> > > > it within put(...)" being too restrictive. My guess is that this was
> > more
> > > > an attempt at describing the basic behavior, and less about requiring
> > the
> > > > reporter only being called within the `put(...)` method and not by
> > methods
> > > > to which `put(...)` synchronously or asynchronously delegates. Can
> you
> > > > confirm whether my assumption is correct? If so, then perhaps my
> > suggestion
> > > > helps work around this issue as well, since there would be no
> > restriction
> > > > on when the reporter is called, and the whole "Order of Operations"
> > section
> > > > could potentially be removed.
> > > >
> > > > Third, it's not clear to me why the "Error Reporter Object"
> subsection
> > in
> > > > the "Proposal" section lists the worker configuration properties that
> > were
> > > > previously introduced with
> > > >
> > > >
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-298%3A+Error+Handling+in+Connect
> > > > .
> > > > Maybe it's worth mentioning that the error reporter functionality
> will
> > > > reuse or build upon KIP-298, including reusing the configuration
> > properties
> > > > defined in KIP-298. But IIUC, the KIP does not propose changing any
> > > > technical or semantic aspect of these configuration properties, and
> > > > therefore the KIP would be more clear and succinct without them.
> > *That* the
> > > > error reporter will use these properties is part of the UX and
> > therefore
> > > > necessary to mention, but *how* it uses those properties is really up
> > to
> > > > the implementation.
> > > >
> > > > Fourth, the "Synchrony" section has a sentence that is confusing, or
> > not as
> > > > clear as it could be.
> > > >
> > > > "If a record is sent to the error reporter, processing of the
> next
> > > > errant record in accept(...) will not begin until the producer
> > successfully
> > > > sends the errant record to Kafka."
> > > >
> > > > This sentence is a bit difficult to understand, but IIUC this really
> > just
> > > > means that "accept(...)" will be synchronous and will block until the
> > > > errant record has been successfully written to Kafka. If so, let's
> say
> > > > that. The rest of the paragraph is fine.
> > > >
> > > > Finally, is this KIP proposing new metrics, or that existing metrics
> > would
> > > > be used to track the error reporter usage? If the former, then please
> > > > fully-specify what these metrics will be, similarly to how metrics
> are
> > > > specified in
> > > >
> > > >
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-196%3A+Add+metrics+to+Kafka+Connect+framework
> > > > .
> > > >
> > > > Thoughts?
> > > >
> > > > Best regards,
> > > >
> > > > Randall
> > > >
> > > > On Mon, May 11, 2020 at 4:49 PM Andrew Schofield <
> > > > andrew_schofi...@live.com>
> > > > wrote:
> > > >
> > > > > Hi Aakash,
> > > > > Thanks for sorting out the replies to the mailing list.
> > > > >
> > > > > First, I do like the idea of improving error reporting in sink
> > > > connectors.
> > > > > I'd like a simple
> > > > > way to put bad records onto the DLQ.
> > > > >
> > > > > I think this KIP is considerably more complicated than it seems.
> The
> > > > > guidance on the
> > > > > SinkTask.put() method is that it should send the records
> > asynchronously
> > > > > and immediately
> > > > > return, so the task is likely to want to report errors
> asynchronously
> > > > > too. Currently the KIP
> > > > > states that "the task can send errant records to it within
> put(...)"
> > and
> > > > > that's too restrictive.
> > > > > The task ought to be able to report any unflushed records, but the
> > > > > synchronisation of this is going
> > > > > to be tricky. I suppose the connector author needs to make sure
> that
> > all
> > > > > errant records have
> > > > > been reported before returning control from SinkTask.flush(...) or
> > > > perhaps
> > > > > SinkTask.preCommit(...).
> > > > >
> > > > > I think the interface is a little strange too. I can see that this
> > was
> > > > > done so it's possible to deliver a connector
> > > > > that supports error reporting but it can also work in earlier
> > versions of
> > > > > the KC runtime. But, the
> > > > > pattern so far is that the task uses the methods of SinkTaskContext
> > to
> > > > > access utilities in the Kafka
> > > > > Connect runtime, and I suggest that reporting a bad record is such
> a
> > > > > utility. SinkTaskContext has
> > > > > changed before when the configs() methods was added, so I think
> > there is
> > > > > precedent for adding a method.
> > > > > The way the KIP adds a method to SinkTask that the KC runtime calls
> > to
> > > > > provide the error reporting utility
> > > > > seems not to match what has gone before.
> > > > >
> > > > > Thanks,
> > > > > Andrew
> > > > >
> > > > > On 11/05/2020, 19:05, "Aakash Shah" <as...@confluent.io> wrote:
> > > > >
> > > > > I wasn't previously added to the dev mailing list, so I'd like
> to
> > > > post
> > > > > my
> > > > > discussion with Andrew Schofield below for visibility and
> further
> > > > > discussion:
> > > > >
> > > > > Hi Andrew,
> > > > >
> > > > > Thanks for the reply. The main concern with this approach would
> > be
> > > > its
> > > > > backward compatibility. I’ve highlighted the thoughts around
> the
> > > > > backwards
> > > > > compatibility of the initial approach, please let me know what
> > you
> > > > > think.
> > > > >
> > > > > Thanks,
> > > > > Aakash
> > > > >
> > > > >
> > > > >
> > > >
> >
> ____________________________________________________________________________________________________________________________
> > > > >
> > > > > Hi,
> > > > > By adding a new method to the SinkContext interface in say
> Kafka
> > > > 2.6, a
> > > > > connector that calls it would require a Kafka 2.6 connect
> > runtime. I
> > > > > don't
> > > > > quite see how that's a backward compatibility problem. It's
> just
> > that
> > > > > new
> > > > > connectors need the latest interface. I might not quite be
> > > > > understanding,
> > > > > but I think it would be fine.
> > > > >
> > > > > Thanks,
> > > > > Andrew
> > > > >
> > > > >
> > > > >
> > > >
> >
> ____________________________________________________________________________________________________________________________
> > > > >
> > > > > Hi Andrew,
> > > > >
> > > > > I apologize for the way the reply was sent. I just subscribed
> to
> > the
> > > > > dev
> > > > > mailing list so it should be resolved now.
> > > > >
> > > > > You are correct, new connectors would simply require the latest
> > > > > interface.
> > > > > However, we want to remove that requirement - in other words,
> we
> > want
> > > > > to
> > > > > allow the possibility that someone wants the latest
> connector/to
> > > > > upgrade to
> > > > > the latest version, but deploys it on an older version of AK.
> > > > > Basically, we
> > > > > don't want to enforce the necessity of upgrading AK to get the
> > latest
> > > > > interface. In the current approach, there would be no issue of
> > > > > deploying a
> > > > > new connector on an older version of AK, as the Connect
> framework
> > > > would
> > > > > simply not invoke the new method.
> > > > >
> > > > > Please let me know what you think and if I need to clarify
> > anything.
> > > > >
> > > > > Thanks,
> > > > > Aakash
> > > > >
> > > > >
> > > >
> > >
> >
> >
>
