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 > > > > > > > > > > > > > > > > > > > > > >