ApsaraMQ for RocketMQ:Methods and parameters

Background information

ApsaraMQ for RocketMQ supports the following modes to obtain messages:

• Push: ApsaraMQ for RocketMQ pushes messages to consumers. In push mode, ApsaraMQ for RocketMQ can push multiple messages to consumers at a time. For more information, see Batch consumption.

• Pull: Consumers pull messages from ApsaraMQ for RocketMQ.

Pull consumers provide more options to receive messages and provide you more control over message pulls than push consumers.

Common parameters

Methods for sending messages

Parameters for sending messages

Methods for subscribing to messages

The following content describes the methods that can be called in pull mode:

public interface PullConsumer extends Admin {

    /**
     * Query the partition information of a topic. This method returns all partitions of the topic. You can call this method only after your pull consumers start to run. 
     */
    Set<TopicPartition> topicPartitions(String topic);

    /**
     * Specify a partition from which you want to pull messages. This method does not implement rebalancing. You must make sure that messages in all partitions can be consumed. If this method is called multiple times, the system replaces the partitions to which subscribers have subscribed instead of increasing the number of partitions to which subscribers subscribe. 
     */
    void assign(Collection<TopicPartition> topicPartitions);

    /**
     * Pull messages. The maxBatchMessageCount parameter specifies the maximum number of messages that can be pulled at a time. You can specify a timeout period in milliseconds. 
     */
    List<Message> poll(long timeout);

    /**
     * Reset the consumer offset of a specified partition to a specified position. The specified position must be between the minimum offset and the maximum offset of the partition. You can call this method only after your pull consumers start to run. A subscriber must subscribe to the specified partition. 
     */
    void seek(TopicPartition topicPartition, long offset);

    /**
     * Reset the consumer offset of a specified partition to the minimum offset of the partition. You can call this method only after your pull consumers start to run. A subscriber must subscribe to the specified partition. 
     */
    void seekToBeginning(TopicPartition topicPartition);

    /**
     * Reset the consumer offset of a specified partition to the maximum offset of the partition. You can call this method only after your pull consumers start to run. A subscriber must subscribe to the specified partition. 
     */
    void seekToEnd(TopicPartition topicPartition);

    /**
     * Suspend message consumption in a specified partition.
     */
    void pause(Collection<TopicPartition> topicPartitions);

    /**
     * Resume message consumption in a specified partition.
     */
    void resume(Collection<TopicPartition> topicPartitions);

    /**
     * Query an offset based on a timestamp in a specified partition. The timestamp indicates when a message is stored to a broker. The offset corresponds to the first timestamp that is greater than or equal to the specified timestamp. 
     */
    Long offsetForTimestamp(TopicPartition topicPartition, Long timestamp);

    /**
     * Query the latest consumer offset of a specified partition.
     */
    Long committed(TopicPartition topicPartition);

    /**
     * Manually commit a consumer offset. The consumer offset is synchronized to your on-premises client and then committed to your broker by using a thread in an asynchronous environment. 
     */
    void commitSync();
    
    interface TopicPartitionChangeListener {
        /**
         * This method is called when the partitions of a topic change, for example, when the number of partitions of a topic changes due to broker scaling. 
         */
        void onChanged(Set<TopicPartition> topicPartitions);
    }
    
    /**
     * Register TopicPartitionChangeListener that listens for changes in the partitions of a topic. The onChanged method can be called back for the registered listener when the number of partitions of a topic changes due to broker scaling. By default, the maximum delay for a callback is five seconds. 
     */
    void registerTopicPartitionChangedListener(String topic, TopicPartitionChangeListener callback);
}

Parameters

For more information about partitions and offsets, see Terms.

References

For more information about the sample code for sending and subscribing to messages, see the following topics:

• Send normal messages in one of three transmission modes

• Send and subscribe to ordered messages

• Send and receive scheduled messages

• Send and receive delayed messages

• Send and receive transactional messages

• Subscribe to messages