Couple of thoughts:
1. If we add new parameters to put(..), and new connectors implement only
this method, it makes them backward incompatible with older workers. I
think newer connectors may only choose to only implement the latest method,
and we are passing the compatibility problems back to the connector
developers.
2. if we deprecate the older put() method and eventually remove it, then
old connectors are forward incompatible. If we are not going to remove it,
then maybe we should not deprecate it?
3. if a record is realized to be erroneous outside put() (say, in flush or
preCommit), how will it be reported?
I do think the concern over aesthetics is an important one, but the
trade-off here is to exclude many connectors that are out there from
running on worker versions. there may be production deployments that need
one old and one new connector that now cannot work on any version of a
single worker. Building connectors is complex, and it's kinda unfair to
expect folks to make changes over aesthetic reasons alone. This is probably
the reason why popular framework APIs very rarely (and probably never)
change.
Overall, yes, the "public void errantRecordReporter(BiConsumer<SinkRecord,
Throwable> reporter) {}" proposal in the original KIP is somewhat of a
mouthful, but are there are any simpler alternatives that do not exclude
existing connectors, adding operational burdens and yet provide a clean
contract?
Best,
PS: Apologies if the language is incorrect or some points are unclear.
On Fri, May 15, 2020 at 12:02 PM Randall Hauch <rha...@gmail.com> wrote:
> On Fri, May 15, 2020 at 1:45 PM Konstantine Karantasis <
> konstant...@confluent.io> wrote:
>
> > Thanks for the quick response Aakash.
> >
> > To your last point, modern APIs like this tend to be asynchronous (see
> > admin, producer in Kafka) and such definition results in more expressive
> > and well defined APIs.
> >
>
> +1
>
>
> > What you describe is easily an opt-in feature for the connector
> developer.
> > At the same time, the latest description above, gives us better chances
> for
> > this API to remain like this for longer, because it covers both the sync
> > and async per `put` user cases.
>
>
> +1
>
>
> > Given how simple the sync implementation
> > is, just by complying with the return type of the method, I still think
> the
> > BiFunction definition that returns a Future makes sense.
> >
> > Konstantine
> >
> >
> >
> > On Fri, May 15, 2020 at 11:27 AM Aakash Shah <as...@confluent.io> wrote:
> >
> > > Thanks for the additional feedback.
> > >
> > > I see the benefits of adding an overloaded put(...) over alternatives
> > and I
> > > am on board going forward with this approach. It will definitely set
> > forth
> > > a contract of where the reporter will be used with better aesthetics.
> > >
> > > The original idea of going with a synchronous approach for the error
> > > reporter was to ease the connector developer's job interacting with and
> > > handling the error reporter. The tradeoff for having a synchronous-only
> > > reporter would be lower throughput on the reporter; this was thought to
> > be
> > > fine since arguably most circumstances would not include consistently
> > large
> > > amounts of records being sent to the error reporter. Even if this was
> the
> > > case, an argument can be made that the lower throughput would be of
> > > assistance in this case, as it would allow more time for the user to
> > > realize the connector is having records sent to the error reporter
> before
> > > many are sent. However, if we are strongly in favor of having the
> option
> > of
> > > asynchronous functionality available for the developer, then I am fine
> > with
> > > that as well.
> > >
> > > Lastly, I am on board with changing the name to failedRecordReporter,
> > >
> > > Please let me know your thoughts.
> > >
> > > Thanks,
> > > Aakash
> > >
> > > 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
> > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > > >
> > > >
> > >
> >
>
