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https://issues.apache.org/jira/browse/KAFKA-7412?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jun Rao resolved KAFKA-7412.
----------------------------
Resolution: Fixed
Fix Version/s: 2.2.0
Clarified the javadoc in producer callback. Metadata is not null with non-null
exception.
Merged the PR to trunk.
> 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
> Assignee: huxihx
> Priority: Major
> Fix For: 2.2.0
>
> 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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