Backends

WARNING

Data storage is an exclusive feature of EMQ X Enterprise.

MQTT Message Persistence

One-to-one message Persistence

1. PUB publishes a message;
2. Backend records this message in DB;
3. SUB subscribes to a topic;
4. Backend retrieves the messages of this topic from DB;
5. Messages are sent to SUB;
6. Once the SUB acknowledged / received the message, backend removes the message from DB.

Many-to-many message Persistence

1. PUB publishes a message;
2. Backend records the message in DB;
3. SUB1 and SUB2 subscribe to a topic;
4. Backend retrieves the messages of this topic;
5. Messages are sent to SUB1 and SUB2;
6. Backend records the read position of SUB1 and SUB2, the next message’s retrieval starts from this position.

Client Connection State

EMQ X supports retaining the client’s connection state in Redis or DB.

Client Subscription by Broker

EMQ X Persistence supports subscription by broker. When a client goes online, the persistence module loads the subscriptions of the client from Redis or Databases.

List of Persistence Plugins

EMQ X allowes storing messages in Redis, MySQL, PostgreSQL, MongoDB, Cassandra, DynamoDB, InfluxDB, OpenTSDB and Timescale: