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Message Queue MQ - Service Overview

Message Queue is a message middleware service that is implemented to enable the application layer to quickly and reliably acquire device messages. The service model is as follows:

Where:

  • topic is a queue entity, and multiple queue entities can be created in one MQ service;
  • sub (subscription) is the actual consumer, a queue can support multiple consumers. Consumers are independent of each other, and can use different modes to consume data in the queue

The message source in the queue is from the product device. The user can forward the needed message to the corresponding queue by configuring the forward rule

Before the user consumes data, he/she first needs to create a topic and sub (subscription), and then use the client to establish a subscription relationship with a sub of a topic to consume the data in the queue

Service Features

  • Message cache

    The MQ service supports message cache, which can effectively cache messages that cannot be consumed immediately due to network or abnormal application server

  • Peak Clipping & Valley Cutting

    The MQ service can effectively buffer large concurrent device messages that burst forward and push them to the consumer client at a lower average rate to reduce the consumer pressure

  • at most once & at least once

    The user can configure message lock time to achieve consumption at most once and consumption at least once message mode. If the message lock time is enabled, and the client does not reply the confirmation within the time, the consumption is considered to be failed. After the lock time, the client can consume the unconfirmed message again

  • Message expiration time The user can configure the message expiration time, i.e., the system will reclaim the message that has entered the queue over a certain period of time

  • Custom consumption location

    Support users to customize the consumption location, such as consumption from the head, consumption from the tail or from a position in the queue. After the setting is completed, the client will consume the message from the custom position in the queue

  • Multi-party independent consumption

    The service supports the user to create multiple consumers for one queue. Consumers are independent of each other and can consume the data in the same queue with different configurations

  • Single consumption & cluster consumption

    The MQ service supports one or more clients to establish a subscription relationship with the same sub (subscription) simultaneously

    When multiple clients simultaneously establish a subscription relationship with the same sub in the same topic, MQ service considers that the client is in the cluster consumption mode, the message will be evenly sent to each client, and each message can only be consumed by one client, as shown in the figure below:

![集群消费](/images/mq/dandianxiaofeiyujiqunxiaofei.png)

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