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https://issues.apache.org/jira/browse/KAFKA-7412?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16626825#comment-16626825
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Michal Turek commented on KAFKA-7412:
-------------------------------------
Hmm, I have just tried to repeat it multiple times with fresh Kafka
installation with default configuration (according to quick start guide). The
callback is now receiving org.apache.kafka.common.errors.TimeoutException
together with non-null RecordMetadata, offset -1, which breaks "Exactly one of
the arguments will be non-null." contract from Javadoc. I still believe there
is something broken inside the client.
{noformat}
/**
* A callback method the user can implement to provide asynchronous
handling of request completion. This method will
* be called when the record sent to the server has been acknowledged.
Exactly one of the arguments will be
* non-null.
* @param metadata The metadata for the record that was sent (i.e. the
partition and offset). Null if an error
* occurred.
* @param exception The exception thrown during processing of this record.
Null if no error occurred.
* Possible thrown exceptions include:
* ...
{noformat}
{noformat}
Metadata AA_INPUT_666-0@-1, exception
org.apache.kafka.common.errors.TimeoutException: Expiring 1 record(s) for
AA_INPUT_666-0: 5036 ms has passed since batch creation plus linger time
{noformat}
!both_metadata_and_exception.png!
I have no idea why it started to behave differently. It's the same code with
the same configuration and versions. This screenshot of debugging has been
taken two weeks ago while creating the task.
!metadata_when_kafka_is_stopped.png!
> Bug prone response from producer.send(ProducerRecord, Callback) if Kafka
> broker is not running
> ----------------------------------------------------------------------------------------------
>
> Key: KAFKA-7412
> URL: https://issues.apache.org/jira/browse/KAFKA-7412
> Project: Kafka
> Issue Type: Bug
> Components: producer
> Affects Versions: 2.0.0
> Reporter: Michal Turek
> Priority: Major
> Attachments: both_metadata_and_exception.png,
> metadata_when_kafka_is_stopped.png
>
>
> Hi there, I have probably found a bug in Java Kafka producer client.
> Scenario & current behavior:
> - Start Kafka broker, single instance.
> - Start application that produces messages to Kafka.
> - Let the application to load partitions for a topic to warm up the producer,
> e.g. send a message to Kafka. I'm not sure if this is necessary step, but our
> code does it.
> - Gracefully stop the Kafka broker.
> - Application logs now contains "org.apache.kafka.clients.NetworkClient:
> [Producer clientId=...] Connection to node 0 could not be established. Broker
> may not be available." so the client is aware about the Kafka unavailability.
> - Trigger the producer to send a message using
> KafkaProducer.send(ProducerRecord, Callback) method.
> - The callback that notifies business code receives non-null RecordMetadata
> and null Exception after request.timeout.ms. The metadata contains offset -1
> which is value of ProduceResponse.INVALID_OFFSET.
> Expected behavior:
> - If the Kafka is not running and the message is not appended to the log, the
> callback should contain null RecordMetadata and non-null Exception. At least
> I subjectively understand the Javadoc this way, "exception on production
> error" in simple words.
> - Developer that is not aware of this behavior and that doesn't test for
> offset -1, may consider the message as successfully send and properly acked
> by the broker.
> Known workaround
> - Together with checking for non-null exception in the callback, add another
> condition for ProduceResponse.INVALID_OFFSET.
> {noformat}
> try {
> producer.send(record, (metadata, exception) -> {
> if (metadata != null) {
> if (metadata.offset() !=
> ProduceResponse.INVALID_OFFSET) {
> // Success
> } else {
> // Failure
> }
> } else {
> // Failure
> }
> });
> } catch (Exception e) {
> // Failure
> }
> {noformat}
> Used setup
> - Latest Kafka 2.0.0 for both broker and Java client.
> - Originally found with broker 0.11.0.1 and client 2.0.0.
> - Code is analogy of the one in Javadoc of KafkaProducer.send().
> - Used producer configuration (others use defaults).
> {noformat}
> bootstrap.servers = "localhost:9092"
> client.id = "..."
> acks = "all"
> retries = 1
> linger.ms = "20"
> compression.type = "lz4"
> request.timeout.ms = 5000 # The same behavior is with default, this is to
> speed up the tests
> {noformat}
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