Channels are connected to message backends using connectors. Connectors are configured to map incoming messages to a specific channel (consumed by the application) and collect outgoing messages sent to a specific channel. Each connector is dedicated to a specific messaging technology. For example, the connector dealing with Kafka is named smallrye-kafka.
If you have a single connector on your classpath, you can omit the connector attribute configuration.Quarkus automatically associates orphan channels to the (unique) connector found on the classpath.Orphans channels are outgoing channels without a downstream consumer or incoming channels without an upstream producer.
Pdf Mq Channel Authentication Records
As with the previous Message example, if your injected channel receives payloads (Multi), it acknowledges the message automatically, and support multiple subscribers.If you injected channel receives Message (Multi), you will be responsible for the acknowledgment and broadcasting.We will explore sending broadcast messages in Broadcasting messages on multiple consumers.
Injecting @Channel("prices") or having @Incoming("prices") does not automatically configure the application to consume messages from Kafka.You need to configure an inbound connector with mp.messaging.incoming.prices... or have an @Outgoing("prices") method somewhere in your application (in which case, prices will be an in-memory channel).
When a message produced from a Kafka record is acknowledged, the connector invokes a commit strategy.These strategies decide when the consumer offset for a specific topic/partition is committed.Committing an offset indicates that all previous records have been processed.It is also the position where the application would restart the processing after a crash recovery or a restart.
throttled keeps track of received messages and commits an offset of the latest acked message in sequence (meaning, all previous messages were also acked).This strategy guarantees at-least-once delivery even if the channel performs asynchronous processing.The connector tracks the received records and periodically (period specified by auto.commit.interval.ms, default: 5000 ms) commits the highest consecutive offset.The connector will be marked as unhealthy if a message associated with a record is not acknowledged in throttled.unprocessed-record-max-age.ms (default: 60000 ms).Indeed, this strategy cannot commit the offset as soon as a single record processing fails.If throttled.unprocessed-record-max-age.ms is set to less than or equal to 0, it does not perform any health check verification.Such a setting might lead to running out of memory if there are "poison pill" messages (that are never acked).This strategy is the default if enable.auto.commit is not explicitly set to true.
latest commits the record offset received by the Kafka consumer as soon as the associated message is acknowledged (if the offset is higher than the previously committed offset).This strategy provides at-least-once delivery if the channel processes the message without performing any asynchronous processing.This strategy should not be used in high load environment, as offset commit is expensive. However, it reduces the risk of duplicates.
ignore performs no commit. This strategy is the default strategy when the consumer is explicitly configured with enable.auto.commit to true.It delegates the offset commit to the underlying Kafka client.When enable.auto.commit is true this strategy DOES NOT guarantee at-least-once delivery.SmallRye Reactive Messaging processes records asynchronously, so offsets may be committed for records that have been polled but not yet processed.In case of a failure, only records that were not committed yet will be re-processed.
To use this failure handler, the bean must be exposed with the @Identifier qualifier and the connector configuration must specify the attribute mp.messaging.incoming.$channel.[keyvalue]-deserialization-failure-handler (for key or value deserializers).
Similar to the previous example, multiple instances of an application can subscribe to a single consumer group, configured via mp.messaging.incoming.$channel.group.id property, or left default to the application name.This in turn will divide partitions of the topic among application instances.
A common business requirement is to consume and process Kafka records in order.The Kafka broker preserves order of records inside a partition and not inside a topic.Therefore, it is important to think about how records are partitioned inside a topic.The default partitioner uses record key hash to compute the partition for a record, or when the key is not defined, chooses a partition randomly per batch or records.
During normal operation, a Kafka consumer preserves the order of records inside each partition assigned to it.Smallrye Reactive Messaging keeps this order for processing, unless @Blocking(ordered = false) is used (see Blocking processing).
By default, incoming methods receive each Kafka record individually.Under the hood, Kafka consumer clients poll the broker constantly and receive records in batches, presented inside the ConsumerRecords container.
Note that the successful processing of the incoming record batch will commit the latest offsets for each partition received inside the batch.The configured commit strategy will be applied for these records only.
Smallrye Reactive Messaging checkpoint commit strategy allows consumer applications to process messages in a stateful manner, while also respecting Kafka consumer scalability.An incoming channel with checkpoint commit strategy persists consumer offsets on an externalstate store, such as a relational database or a key-value store.As a result of processing consumed records, the consumer application can accumulate an internal state for each topic-partition assigned to the Kafka consumer.This local state will be periodically persisted to the state store and will be associated with the offset of the record that produced it.
The @Incoming channel consumer code can manipulate the processing state through the CheckpointMetadata API.For example, a consumer calculating the moving average of prices received on a Kafka topic would look the following:
The checkpoint commit strategy tracks when a processing state is last persisted for each topic-partition.If an outstanding state change can not be persisted for checkpoint.unsynced-state-max-age.ms (default: 10000), the channel is marked unhealthy.
State store implementations determine where and how the processing states are persisted.This is configured by the mp.messaging.incoming.[channel-name].checkpoint.state-store property.The serialization of state objects depends on the state store implementation.In order to instruct state stores for serialization can require configuring the class name of state objects using mp.messaging.incoming.[channel-name].checkpoint.state-type property.
quarkus-redis: Uses the quarkus-redis-client extension to persist processing states.Jackson is used to serialize processing state in Json. For complex objects it is required to configure the checkpoint.state-type property with the class name of the object.By default, the state store uses the default redis client, but if a named client is to be used, the client name can be specified using the mp.messaging.incoming.[channel-name].checkpoint.quarkus-redis.client-name property.Processing states will be stored in Redis using the key naming scheme [consumer-group-id]:[topic]:[partition].
To use this failure handler, the bean must be exposed with the @Identifier qualifier and the connector configuration must specify the attribute mp.messaging.outgoing.$channel.[keyvalue]-serialization-failure-handler (for key or value serializers).
The framework verifies that the producer/consumer chain is complete,meaning that if the application writes messages into an in-memory channel (using a method with only @Outgoing, or an Emitter),it must also consume the messages from within the application (using a method with only @Incoming or using an unmanaged stream).
By default, a channel can be linked to a single consumer, using @Incoming method or @Channel reactive stream.At application startup, channels are verified to form a chain of consumers and producers with single consumer and producer.You can override this behavior by setting mp.messaging.$channel.broadcast=true on a channel.
Reciprocally, multiple producers on the same channel can be merged by setting mp.messaging.incoming.$channel.merge=true.On the @Incoming methods, you can control how multiple channels are merged using the @Merge annotation.
Kafka transactions enable atomic writes to multiple Kafka topics and partitions.The Kafka connector provides KafkaTransactions custom emitter for writing Kafka records inside a transaction.It can be injected as a regular emitter @Channel:
Kafka transactional producers require configuring acks=all client property, and a unique id for transactional.id, which implies enable.idempotence=true.When Quarkus detects the use of KafkaTransactions for an outgoing channel it configures these properties on the channel,providing a default value of "$quarkus.application.name-$channelName" for transactional.id property.
The Uni returned from the KafkaTransactions#withTransaction will yield a failure if the transaction fails and is aborted.The application can choose to handle the error case, but if a failing Uni is returned from the @Incoming method, the incoming channel will effectively fail and stop the reactive stream.
The KafkaTransactions#withTransactionAndAck method acks and nacks the message but will not return a failing Uni.Nacked messages will be handled by the failure strategy of the incoming channel, (see Error Handling Strategies).Configuring failure-strategy=ignore simply resets the Kafka consumer to the last committed offsets and resumes the consumption from there.
Using the health-topic-verification-enabled=true attribute, startup probe uses an admin client to check for the list of topics.Whereas the readiness probe for an incoming channel checks that at least one partition is assigned for consumption,and for an outgoing channel checks that the topic used by the producer exist in the broker. 2ff7e9595c
Comments