On Fri, May 15, 2020 at 3:13 PM Arjun Satish <arjun.sat...@gmail.com> wrote:
> 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.
>
New connectors would have to implement both if they want to run in older
runtimes.
> 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?
>
I don't think we'll ever remove deprecated methods -- there's no reason to
cut off older connectors.
> 3. if a record is realized to be erroneous outside put() (say, in flush or
> preCommit), how will it be reported?
>
This is a concern no matter how the reporter is passed to the task.
Actually, I think it's more clear that the reporter passed through
`put(...)` should be used to record errors on the SinkRecords passed in the
same method call.
>
> 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.
>
I don't see how passing the reporter through an overloaded `put(...)` is
less backward compatible. Because the runtime provides the SinkTask base
class, the runtime has control over what the methods do by default.
>
> 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?
>
IMO, overloading `put(...)` is cleaner and easier to understand -- plus the
other benefits in my earlier email.
>
> 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
> > > > > > > > >
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>
