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Posted to dev@kafka.apache.org by "Eno Thereska (JIRA)" <ji...@apache.org> on 2017/05/24 12:43:04 UTC
[jira] [Commented] (KAFKA-4740) Using new consumer API with a
Deserializer that throws SerializationException can lead to infinite loop
[ https://issues.apache.org/jira/browse/KAFKA-4740?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16022828#comment-16022828 ]
Eno Thereska commented on KAFKA-4740:
-------------------------------------
I mentioned in KAFKA-5211 that such a change should be done with a KIP.
> Using new consumer API with a Deserializer that throws SerializationException can lead to infinite loop
> -------------------------------------------------------------------------------------------------------
>
> Key: KAFKA-4740
> URL: https://issues.apache.org/jira/browse/KAFKA-4740
> Project: Kafka
> Issue Type: Bug
> Components: clients, consumer
> Affects Versions: 0.9.0.0, 0.9.0.1, 0.10.0.0, 0.10.0.1, 0.10.1.0, 0.10.1.1
> Environment: Kafka broker 0.10.1.1 (but this bug is not dependent on the broker version)
> Kafka clients 0.9.0.0, 0.9.0.1, 0.10.0.0, 0.10.0.1, 0.10.1.0, 0.10.1.1
> Reporter: Sébastien Launay
> Assignee: Sébastien Launay
> Priority: Critical
>
> The old consumer supports deserializing records into typed objects and throws a {{SerializationException}} through {{MessageAndMetadata#key()}} and {{MessageAndMetadata#message()}} that can be catched by the client \[1\].
> When using the new consumer API with kafka-clients version < 0.10.0.1, such the exception is swallowed by the {{NetworkClient}} class and result in an infinite loop which the client has no control over like:
> {noformat}
> DEBUG org.apache.kafka.clients.consumer.internals.Fetcher - Resetting offset for partition test2-0 to earliest offset.
> DEBUG org.apache.kafka.clients.consumer.internals.Fetcher - Fetched offset 0 for partition test2-0
> ERROR org.apache.kafka.clients.NetworkClient - Uncaught error in request completion:
> org.apache.kafka.common.errors.SerializationException: Size of data received by IntegerDeserializer is not 4
> ERROR org.apache.kafka.clients.NetworkClient - Uncaught error in request completion:
> org.apache.kafka.common.errors.SerializationException: Size of data received by IntegerDeserializer is not 4
> ...
> {noformat}
> Thanks to KAFKA-3977, this has been partially fixed in 0.10.1.0 but another issue still remains.
> Indeed, the client can now catch the {{SerializationException}} but the next call to {{Consumer#poll(long)}} will throw the same exception indefinitely.
> The following snippet (full example available on Github \[2\] for most released kafka-clients versions):
> {code:java}
> try (KafkaConsumer<String, Integer> kafkaConsumer = new KafkaConsumer<>(consumerConfig, new StringDeserializer(), new IntegerDeserializer())) {
> kafkaConsumer.subscribe(Arrays.asList("topic"));
> // Will run till the shutdown hook is called
> while (!doStop) {
> try {
> ConsumerRecords<String, Integer> records = kafkaConsumer.poll(1000);
> if (!records.isEmpty()) {
> logger.info("Got {} messages", records.count());
> for (ConsumerRecord<String, Integer> record : records) {
> logger.info("Message with partition: {}, offset: {}, key: {}, value: {}",
> record.partition(), record.offset(), record.key(), record.value());
> }
> } else {
> logger.info("No messages to consume");
> }
> } catch (SerializationException e) {
> logger.warn("Failed polling some records", e);
> }
> }
> }
> {code}
> when run with the following records (third record has an invalid Integer value):
> {noformat}
> printf "\x00\x00\x00\x00\n" | bin/kafka-console-producer.sh --broker-list localhost:9092 --topic topic
> printf "\x00\x00\x00\x01\n" | bin/kafka-console-producer.sh --broker-list localhost:9092 --topic topic
> printf "\x00\x00\x00\n" | bin/kafka-console-producer.sh --broker-list localhost:9092 --topic topic
> printf "\x00\x00\x00\x02\n" | bin/kafka-console-producer.sh --broker-list localhost:9092 --topic topic
> {noformat}
> will produce the following logs:
> {noformat}
> INFO consumer.Consumer - Got 2 messages
> INFO consumer.Consumer - Message with partition: 0, offset: 0, key: null, value: 0
> INFO consumer.Consumer - Message with partition: 0, offset: 1, key: null, value: 1
> WARN consumer.Consumer - Failed polling some records
> org.apache.kafka.common.errors.SerializationException: Error deserializing key/value for partition topic-0 at offset 2
> Caused by: org.apache.kafka.common.errors.SerializationException: Size of data received by IntegerDeserializer is not 4
> WARN consumer.Consumer - Failed polling some records
> org.apache.kafka.common.errors.SerializationException: Error deserializing key/value for partition topic-0 at offset 2
> Caused by: org.apache.kafka.common.errors.SerializationException: Size of data received by IntegerDeserializer is not 4
> WARN consumer.Consumer - Failed polling some records
> org.apache.kafka.common.errors.SerializationException: Error deserializing key/value for partition topic-0 at offset 2
> Caused by: org.apache.kafka.common.errors.SerializationException: Size of data received by IntegerDeserializer is not 4
> ...
> {noformat}
> I don't believe committing offsets would help and even if it did this could potentially result in a few well formed records not being consumed from that {{ConsumerRecords}} batch (data loss).
> I have only seen a few mentions of this bug online \[3\] but I believe this is a critical issue as the new consumer API is not in beta anymore yet if you do not control producers (that can inject malformed values) or you use some advanced deserializer that throws such exception (e.g. schema-registry {{KafkaAvroDeserializer}}) then you can end up blocking a consumer from advancing in the stream.
> Current workarounds:
> - use a {{Deserializer}} that do not throw a {{SerializationException}} (e.g. {{ByteArrayDeserializer}}, {{StringDeserializer}})
> - wrap the {{Deserializer}} to catch and log the {{SerializationException}} but return {{null}} and then check for {{null}} in the client code (that's what we use on top of {{KafkaAvroDeserializer}} in case there is an issue reaching the schema registry or the Avro datum is either invalid or not compatible with the reader's schema for some reason)
> Potential solutions:
> # continue to throw {{SerializationException}} when calling {{Consumer#poll(long)}} but skip that malformed record on next {{Consumer#poll(long)}}
> # do not throw {{SerializationException}} when calling {{Consumer#poll(long)}} but expose information about invalid records in {{ConsumerRecords}}
> # do not throw {{SerializationException}} when calling {{Consumer#poll(long)}} but store the exception(s) in the {{ConsumerRecord}} object record so that it is rethrown on {{ConsumerRecord#key()}} and {{ConsumerRecord#value()}}
> # do not deserialize records during {{Consumer#poll()}} but do it when calling {{ConsumerRecord#key()}} and {{ConsumerRecord#value()}} (similar to the old consumer)
> I believe any of those solutions breaks compatibility semantic wise but not necessary binary compatibility as the {{SerializationException}} is a {{RuntimeException}} so it could be "moved around".
> My preference goes to the two last ones and I would be happy to contribute such a change as well as update the documentation on {{SerializationException}} to reflect that it is not only used for serializing records.
> \[1\] https://github.com/apache/kafka/blob/0.8.2.2/core/src/main/scala/kafka/message/MessageAndMetadata.scala
> \[1\] http://docs.confluent.io/2.0.0/schema-registry/docs/serializer-formatter.html#serializer
> \[2\] https://github.com/slaunay/kafka-consumer-serialization-exception-example
> \[3\] https://groups.google.com/forum/#!topic/kafka-clients/KBSPmY69H94
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