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This KIP is aimed at improving the error-handling semantics in Kafka Streams when Kafka Steams fails to produce a message to the downstream sink by providing an interface that can provide custom massaging of the error (e.g. report to a custom metrics system) and indicate to Streams whether or not it should re-throw the Exception, thus causing the application to fall over.
Status
Current state: Under Discussion Adopted (1.1.0)
Discussion thread: Click here
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At MailChimp, we've run into occasional situations where a message that comes into streams just under the size limit on the inbound size (say for the sake of illustration, 950KB with a 1MB max.request.size
on the Producer) and we change it to a different serialization format for producing to the destination topic. In these cases, it's possible that the serialization format we change to comes in as larger than the inbound message. (For example, if we were going from a binary format to JSON we might get something much larger than if the inbound format was a binary format of some kindon the outbound side.)
These cases are rare, but when they occur they cause our entire application to fall over and someone gets woken up in the middle of the night to figure out how to deal with it. Further, solutions that address this issue by hacking around it (increasing the max.request.size or trying to manually commit to the offsets topic to skip the large messages) each have their own problems. It would be preferable for us to be able to optionally provide code to ignore an ApiException
returned from the producer. Such an interface would permit us to provide code that will log an error and instruct Streams to not re-throw the error.
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We are proposing the addition of:
- A public enumeration,
ProductionExceptionHandlerResponse
, with two possible values:CONTINUE
andFAIL
- A public interface named
ProductionExceptionProcessor
withProductionExceptionHandler
with a single method,processException
, that accepts anException
and returns aboolean
, such thattrue
indicates that the error should be re-thrown by Streams andfalse
indicates it should nothandle
, that has the following signature:ProductionExceptionHandlerResponse handle(ProducerRecord<byte[], byte[]> record, Exception exception)
- One default implementation of ProductionExceptionHandler
- The
DefaultProductionExceptionHandler
, the default implementation that maintains the current behavior of always failing when production exceptions occur.
- The
- A new configuration parameter for Streams named
default.production.exception.processor.class
thathandler
that accepts the fully qualified class name of theProductionExceptionProcessor
ProductionExceptionHandler
to use.
Proposed Changes
This implementation will modify the KafkaStreams
constructor to create a ProductionExceptionProcessor
ProductionExceptionHandler
from the aforementioned config value, defaulting to a default implementation that always re-throws the error (the DefaultProductionExceptionHandler
mentioned above). We'll pipe this processor through the StreamThread
/StreamTask
into RecordCollectorImpl
.
We'll make a change to the onCompletion handler in RecordCollectorImpl to execute the processException
method in its ProductionExceptionProcessor
and only record the exception in sendException
if processException
returns true
.implement the following error handling logic to the onCompletion handler in RecordCollectorImpl:
- If the Exception that is thrown is a
ProducerFencedException
, behave as we do today and do not invoke theProductionExceptionHandler
as these exceptions are self-healing. - If the Exception that is thrown is fatal will affect all records and should cause Streams to always fail. If so, then do not invoke the
ProductionExceptionHandler
because its result will have to be ignored. We should log that we're ignoring these exceptions at DEBUG level.- The exceptions that meet this classification are:
AuthenticationException
AuthorizationException
SecurityDisabledException
InvalidTopicException
UnknownServerException
IllegalStateException
OffsetMetadataTooLarge
SerializationException
TimeoutException
when it occurs immediately on send due to a full buffer
- The exceptions that meet this classification are:
- If the
Exception
that is thrown meets neither of the above conditions, determine ifsendException
is already set. If so, do not invoke theProductionExceptionHandler
because this would mean that we've already invoked it and decided toFAIL
. Invoking it again would just result in an ignored result. - If none of the conditions above is met, invoke the
handle
method in theProductionExceptionHandler
and check the result.- If the result is
CONTINUE
, log a note atDEBUG
that we received that result and are not failing Streams as a result. This ensures that it's not possible for a client developer to ship code that totally swallows errors without presenting any kind of activity in the log. - If the result is
FAIL
, log a message atERROR
that we received that result and setsendException
so Streams will fail.
- If the result is
The error handler will only be invoked for exceptions that are returned via the producer callback, and will not be invoked for Exceptions thrown directly from send as all of those exceptions should be seen by Streams immediately.
These changes will facilitate a number of error handling scenarios. For example, one could choose to write an interface that always fails, but does some additional logging in the process:
Code Block | ||
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class ExtraLoggingProductionExceptionHandler extends ProductionExceptionHandler {
ProductionExceptionHandlerResponse handle(ProducerRecord <byte[], byte[]> record, Exception exception) {
val keyString = new String(record.key(), "UTF-8");
logger.error("Got an error! Key: " + keyString, exception);
return ProductionExceptionHandlerResponse.FAIL;
}
} |
You could also create a similar interface that just continues processing and logs a warning:
Code Block | ||
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| ||
class ExtraLoggingProductionExceptionHandler extends ProductionExceptionHandler {
ProductionExceptionHandlerResponse handle(ProducerRecord <byte[], byte[]> record, Exception exception) {
val keyString = new String(record.key(), "UTF-8");
logger.warn("Got an error! Key: " + keyString, exception);
return ProductionExceptionHandlerResponse.CONTINUE;
}
} |
Compatibility, Deprecation, and Migration Plan
The default behavior here will be consistent with existing behavior. Changing that behavior will be opt-in by providing the new config setting and an implementation of the interface. Constructors of RecordCollectorImpl
, StreamThread
, and StreamTask
will need to change, but as those aren't (to my knowledge) part of the public interface, so that should be fine. We could even provide overloaded constructors with the old signatures if we're concerned about binary compatibility of this change.
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