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    ApsaraMQ for RocketMQ:Messages

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    ApsaraMQ for RocketMQ:Messages

    Last Updated:Oct 27, 2025

    This topic describes the definition, model relationship, internal attributes, behavior constraints, and usage notes for messages in ApsaraMQ for RocketMQ.

    Definition

    A message is the smallest unit of data transmission in ApsaraMQ for RocketMQ. A producer encapsulates the payload and extended attributes of business data into a message and sends the message to an ApsaraMQ for RocketMQ broker. The broker then delivers the message to a consumer based on the relevant semantics.

    The message model of ApsaraMQ for RocketMQ has the following features:

    • Immutability

      A message is an event that is generated. After the message is generated, the content of the message does not change. Even if the message passes through a transmission channel, the content of the message remains the same. The messages that consumers obtain are read-only messages.

    • Persistence

      By default, ApsaraMQ for RocketMQ persists messages by storing them in files on the ApsaraMQ for RocketMQ broker. This ensures that messages can be traced and recovered in the event of a system failure.

    Model relationship

    The following figure shows the position of messages in the domain model of ApsaraMQ for RocketMQ.消息

    1. Messages are initialized by producers and sent to the ApsaraMQ for RocketMQ broker.

    2. Messages are stored in queues in the order they are received by the ApsaraMQ for RocketMQ broker.

    3. Consumers obtain and consume messages from the ApsaraMQ for RocketMQ broker according to their subscription relationships.

    Internal attributes

    System attributes

    Topic name

    • Definition: The name of the topic to which a message belongs. The topic name is globally unique within a cluster. For more information, see Topics.

    • Value: Obtained from the SDK interface.

    Lite topic name

    • Definition: The name of the lite topic to which the message belongs. If the topic type is Lite, the name is globally unique within that topic. For more information, see Lite topic model.

    • Value: Obtained from the SDK interface.

    Message type

    • Definition: The type of a message.

    • Value: Obtained from the SDK interface. ApsaraMQ for RocketMQ supports the following message types:

      • Normal: Normal messages. A normal message has no special semantics and is not correlated with other messages.

      • FIFO: Ordered messages. ApsaraMQ for RocketMQ uses a message group (MessageGroup) to specify the order of a set of messages. This ensures that messages are delivered in the exact order in which they are sent.

      • Delay: Scheduled and delayed messages. You can specify a time delay to prevent a message from being delivered immediately after it is sent. The message becomes visible to consumers only after the specified delay.

      • Transaction: Transactional messages. ApsaraMQ for RocketMQ supports distributed transactional messages. It ensures transactional consistency for database updates and message calls.

      • Lite: Lite messages. The LiteTopic feature is available only for topics with the Lite message type.

    Message queue

    • Definition: The queue where the message is stored. For more information, see Message queues.

    • Value: Specified and populated by the broker.

    Message offset

    • Definition: The position of the message within its queue. For more information, see Consumption progress.

    • Value: Specified and populated by the broker. Valid values: 0 to Long.Max.

    Message ID

    • Definition: The unique identifier of a message. Each message ID is globally unique within the cluster.

    • Value: Automatically generated by the producer client. A message ID is a 32-character string that consists of digits and uppercase letters.

    (Optional) Index key list

    • Definition: The index keys for a message. You can set keys to categorize messages and retrieve them quickly.

    • Value: Defined by the producer client.

    (Optional) Filter tag

    • Definition: The tag used to filter messages. Consumers can filter messages by tags to receive only messages that have the specified tags.

    • Value: Defined by the producer client.

    • Constraint: You can specify only one tag for a message.

    (Optional) Scheduled time

    • Definition: In scheduled delivery scenarios, this is the timestamp in milliseconds when the message is delivered. For more information, see Scheduled and delayed messages.

    • Value: Defined by the message producer.

    • Constraints:

      • Subscription and pay-as-you-go Standard Edition instances, and Serverless Standard and Professional Edition instances: A maximum of 7 days.

      • Subscription and pay-as-you-go Professional Edition and Platinum Edition instances: A maximum of 40 days.

      For more information, see Quotas and limits.

    Message sending time

    • Definition: The local timestamp in milliseconds of the producer client when the message is sent.

    • Value: Populated by the producer client.

    • Note: The client clock may differ from the broker clock. The message sending time is based on the client clock.

    Message retention timestamp

    • Definition: The local timestamp in milliseconds of the ApsaraMQ for RocketMQ broker when the message is stored.

      For scheduled messages and transactional messages, the message retention time is the broker time that is displayed for the consumer when the message takes effect.

    • Value: Populated by the broker.

    • Note: The client clock may differ from the broker clock. The message retention time is based on the broker clock.

    Number of consumption retries

    • Definition: The number of times that the ApsaraMQ for RocketMQ broker redelivers a message after consumption fails. The number of retries increases by 1 after each retry attempt. For more information, see Consumption retry.

    • Value: Marked by the broker. The number of retries is 0 for the first consumption attempt. After a consumption failure, the number of retries for the first retry attempt is 1.

    Custom attributes for messages

    Custom attributes

    • Definition: Extended information that a producer can customize.

    • Value: Defined by the message producer as key-value pairs of strings.

    Message load

    Message load

    • Definition: The payload of a business message.

    • Value: Serialized and encoded by the producer and transmitted as a binary byte array.

    • Constraints: For more information, see Parameter limits.

    Behavior constraints

    The size of a message cannot exceed the upper limit. If the size of a message exceeds the corresponding upper limit, the message fails to be sent.

    The default maximum message sizes are as follows:

    • Normal and ordered messages: 4 MB

    • Transactional, scheduled, and delayed messages: 64 KB

    Usage notes

    Overloaded transmission is not recommended for a single message.

    As a messaging middleware, ApsaraMQ for RocketMQ is designed to transmit business event data. We recommend that you control the data size of a single message. An excessively large message can increase the load on the network transport layer and is not ideal for features such as retries and traffic shaping.

    If an overloaded transmission is required in the production environment, we recommend that you split the message based on a fixed size or use the file storage method.

    Immutability of messages

    In ApsaraMQ for RocketMQ 5.x brokers, messages are immutable. Consumers obtain read-only message views.

    Because 3.x and 4.x versions do not have immutability constraints, you must re-initialize the messages if you want to forward them.

    • Correct example:

      Message m = Consumer.receive();
Message m2= MessageBuilder.buildFrom(m);
Producer.send(m2);

    • Incorrect example:

      Message m = Consumer.receive();
m.update();
Producer.send(m);