The type safety issue is definitely not solved by having two separate
callbacks. I just think it gets a bit worse by mashing them into one
method. At least in the plain #handle method you can be sure that the type
is ProducerRecord<byte[], byte[]> and in #handleSerialization the type is
some POJO.
And in theory you can just embed the mapping of sink topics to type/Serde
based on your topology. Or let's say your output record keys & values are
all Strings, and you want to print the String representation in your
handler, rather than the bytes.
Having a separate callback means knowing you can simply print the
ProducerRecord's key/value in the #handleSerialization method, and will
have to use a StringDeserializer to convert the key/value to its String
form to print it in the #handle method.
Again, I just feel this will be more straightforward and easy for users to
use correctly, but am satisfied either way. I'll shut up now and wait for
the KIP authors to make a call on this one way or another, and then I'm
happy to cast my vote
On Thu, May 9, 2024 at 10:15 AM Matthias J. Sax <mj...@apache.org> wrote:
> Thanks Sophie! Makes it much clearer where you are coming from.
>
> About the Type unsafety: isn't this also an issue for the
> `handleSerialziationException` case, because the handler is used for all
> sink topics, and thus key/value types are not really know w/o taking the
> sink topic into account? -- So I am not sure if having two handler
> methods really helps much with regard to type safety?
>
> Just want to make this small comment for completeness. Let's hear what
> others think. Given that we both don't have a strong opinion but just a
> personal preference, we should be able to come to a conclusion quickly
> and get this KIP approved for 3.8 :)
>
>
> -Matthias
>
> On 5/8/24 3:12 PM, Sophie Blee-Goldman wrote:
> > Well I definitely don't feel super strongly about it, and more
> importantly,
> > I'm not a user. So I will happily defer to the preference of anyone who
> > will actually be using this feature. But I'll explain my reasoning:
> >
> > There *is* a relevant distinction between these two callbacks -- because
> > the passed-in record will have a different type depending on whether it
> was
> > a serialization exception or something else. Even if we combined them
> into
> > a single #handle method, users will still end up implementing two
> distinct
> > branches depending on whether it was a serialization exception or not,
> > since that determines the type of the ProducerRecord passed in.
> >
> > Not to mention they'll need to cast it to a ProducerRecord<byte[],
> byte[]>
> > when we could have just passed it in as this type via a dedicated
> callback.
> > And note that because of the generics, they can't do an instanceof check
> to
> > make sure that the record type is ProducerRecord<byte[], byte[]> and will
> > have to suppress the "unchecked cast" warning.
> >
> > So if we combined the two callbacks, their handler will look something
> like
> > this:
> >
> > @SuppressWarnings("unchecked")
> > public ProductionExceptionHandlerResponse handle(final
> ErrorHandlerContext
> > context,
> > final ProducerRecord<?, ?> record,
> > final Exception exception) {
> > if (exception instanceof SerializationException) {
> > if (exception.origin().equals(KEY)) {
> > log.error("Failed to serialize key", exception);
> > } else {
> > log.error("Failed to serialize value", exception);
> > }
> >
> > } else {
> > final ProducerRecord<byte[], byte[]> serializedRecord =
> (ProducerRecord<byte[],
> > byte[]>) record;
> > log.error("Failed to produce record with serialized key={} and serialized
> > value={}",
> > serializedRecord.key(), serializedRecord.value());
> > }
> > return ProductionExceptionHandlerResponse.FAIL;
> > }
> >
> > That seems like the most basic case, and it still haswith distinct logic
> > even if they ultimately handle exceptions the same way. And looking
> forward
> > to KIP-1034: Dead-letter queues, it seems all the more likely that the
> > actual handling response might be different depending on whether it's a
> > serialization exception or not: a serialized record can probably be
> > retried/sent to a DLQ, whereas a record that can't be serialized should
> not
> > (can't, really) be forwarded to a DLQ. So if they're going to have
> > completely different implementations depending on whether it's a
> > serialization exception, why not just give them two separate callbacks?
> >
> > And that's all assuming the user is perfectly aware of the different
> > exception types and their implications for the type of the
> ProducerRecord.
> > Many people might just miss the existence of the
> > RecordSerializationException altogether --
> > there are already so many different exception types, ESPECIALLY when it
> > comes to the Producer. Not to mention they'll need to understand the
> > nuances of how the ProducerRecord type changes depending on the type of
> > exception that's passed in. And on top of all that, they'll need to know
> > that there is metadata stored in the RecordSerializationException
> regarding
> > the origin of the error. Whereas if we just passed in the
> > SerializationExceptionOrigin to a #handlerSerialization callback, well,
> > that's pretty impossible to miss.
> >
> > That all just seems like a lot for most people to have to understand to
> > implement a ProductionExceptionHandler, which imo is not at all an
> advanced
> > feature and should be as straightforward and easy to use as possible.
> >
> > Lastly -- I don't think it's quite fair to compare this to the
> > RecordDeserializationException. We have a dedicated handler that's just
> for
> > deserialization exceptions specifically, hence there's no worry about
> users
> > having to be aware of the different exception types they might have to
> deal
> > with in the DeserializtionExceptionHandler. Whereas serialization
> > exceptions are just a subset of what might get passed in to the
> > ProductionExceptionHandler...
> >
> > Just explaining my reasoning -- in the end I leave it up to the KIP
> authors
> > and anyone who will actually be using this feature in their applications
> :)
> >
> >
> >
> > On Tue, May 7, 2024 at 8:35 PM Matthias J. Sax <mj...@apache.org> wrote:
> >
> >> @Loic, yes, what you describe is exactly what I had in mind.
> >>
> >>
> >>
> >> @Sophie, can you elaborate a little bit?
> >>
> >>> First of all, I agree that it makes sense to maintain the two separate
> >>> callbacks for the ProductionExceptionHandler, since one of them is
> >>> specifically for serialization exceptions while the other is used for
> >>> everything/anything else.
> >>
> >> What makes a serialization exception special compare to other errors
> >> that it's valuable to treat it differently? Why can we put "everything
> >> else" into a single bucket? By your train of though, should we not split
> >> out the "everything else" bucket into a different callback method for
> >> every different error? If no, why not, but only for serialization
> errors?
> >>
> >> From what I believe to remember, historically, we added the
> >> ProductionExceptionHandler, and kinda just missed the serialization
> >> error case. And later, when we extended the handler we just could not
> >> re-use the existing callback as it was typed with `<byte[], byte[]>` and
> >> it would have been an incompatible change; so it was rather a workaround
> >> to add the second method to then handler, but not really intended
> design?
> >>
> >>
> >> It's of course only my personal opinion that I believe a single callback
> >> method is simpler/cleaner compared to sticking with two, and adding the
> >> new exception type to make it backward compatible seems worth it. It
> >> also kinda introduces the same patter we use elsewhere (cf KIP-1036)
> >> what I actually think is an argument for introducing
> >> `RercordSerializationExcetpion`, to unify user experience across the
> board.
> >>
> >> Would be great to hear from others about this point. It's not that I
> >> strongly object to having two methods, and I would not block this KIP on
> >> this question.
> >>
> >>
> >>
> >> -Matthias
> >>
> >>
> >> On 5/7/24 3:40 PM, Sophie Blee-Goldman wrote:
> >>> First of all, I agree that it makes sense to maintain the two separate
> >>> callbacks for the ProductionExceptionHandler, since one of them is
> >>> specifically for serialization exceptions while the other is used for
> >>> everything/anything else. I also think we can take advantage of this
> fact
> >>> to simplify things a bit and cut down on the amount of new stuff added
> to
> >>> the API by just adding a parameter to the #handleSerializationException
> >>> callback and use that to pass in the SerializationExceptionOrigin enum
> to
> >>> distinguish between key vs value. This way we wouldn't need to
> introduce
> >>> yet another exception type (the RecordSerializationException) just to
> >> pass
> >>> in this information.
> >>>
> >>> Thoughts?
> >>>
> >>> On Tue, May 7, 2024 at 8:33 AM Loic Greffier <
> loic.greff...@michelin.com
> >>>
> >>> wrote:
> >>>
> >>>> Hi Matthias,
> >>>>
> >>>> To sum up with the ProductionExceptionHandler callback methods (106)
> >>>> proposed changes.
> >>>>
> >>>> A new method ProductionExceptionHandler#handle is added with the
> >> following
> >>>> signature:
> >>>>
> >>>>> ProductionExceptionHandlerResponse handle(final ErrorHandlerContext
> >>>> context, final ProducerRecord<?,?> record, final Exception exception);
> >>>>
> >>>> The ProducerRecord<?,?> parameter has changed to accept a serialized
> or
> >>>> non-serialized record.
> >>>> Thus, the new ProductionExceptionHandler#handle method can handle both
> >>>> production exception and serialization exception.
> >>>>
> >>>> Both old ProductionExceptionHandler#handle and
> >>>> ProductionExceptionHandler#handleSerializationException methods are
> now
> >>>> deprecated.
> >>>> The old ProductionExceptionHandler#handle method gets a default
> >>>> implementation, so users do not have to implement a deprecated method.
> >>>>
> >>>> To handle backward compatibility, the new
> >>>> ProductionExceptionHandler#handle method gets a default
> implementation.
> >>>>
> >>>>> default ProductionExceptionHandlerResponse handle(final
> >>>> ErrorHandlerContext context, final ProducerRecord<?, ?> record, final
> >>>> Exception exception) {
> >>>>> if (exception instanceof RecordSerializationException) {
> >>>>> this.handleSerializationException(record,
> exception.getCause());
> >>>>> }
> >>>>>
> >>>>> return handle((ProducerRecord<byte[], byte[]>) record,
> exception);
> >>>>> }
> >>>>
> >>>> The default implementation either invokes
> #handleSerializationException
> >> or
> >>>> #handle depending on the type of the exception, thus users still
> >> relying on
> >>>> deprecated ProductionExceptionHandler#handle
> >>>> or ProductionExceptionHandler#handleSerializationException custom
> >>>> implementations won't break.
> >>>>
> >>>> The new ProductionExceptionHandler#handle method is now invoked in
> case
> >> of
> >>>> serialization exception:
> >>>>
> >>>>> public <K, V> void send(final String topic, final K key, final V
> value,
> >>>> ...) {
> >>>>> try {
> >>>>> keyBytes = keySerializer.serialize(topic, headers, key);
> >>>>> ...
> >>>>> } catch (final ClassCastException exception) {
> >>>>> ...
> >>>>> } catch (final Exception exception) {
> >>>>>
> >>>>> try {
> >>>>> response = productionExceptionHandler.handle(context,
> >>>> record, new
> >> RecordSerializationException(SerializationExceptionOrigin.KEY,
> >>>> exception));
> >>>>> } catch (final Exception e) {
> >>>>> ...
> >>>>> }
> >>>>> }
> >>>>> }
> >>>>
> >>>> To wrap the origin serialization exception and determine whether it
> >> comes
> >>>> from the key or the value, a new exception class is created:
> >>>>
> >>>>> public class RecordSerializationException extends
> >> SerializationException
> >>>> {
> >>>>> public enum SerializationExceptionOrigin {
> >>>>> KEY,
> >>>>> VALUE
> >>>>> }
> >>>>>
> >>>>> public
> RecordSerializationException(SerializationExceptionOrigin
> >>>> origin, final Throwable cause);
> >>>>> }
> >>>>
> >>>> Hope it all makes sense,
> >>>> Loïc
> >>>>
> >>>
> >>
> >
>
