RocketMQ message queue cluster mainly includes four roles: NameServer, Broker (Master/Slave), Producer and Consumer. The basic communication process is as follows:
(1) After Broker start-up, it needs to complete one operation: register itself to NameServer, and then report Topic routing information to NameServer at regular intervals of 30 seconds.
(2) When message producer Producer sends a message as a client, it needs to obtain routing information from the local cache TopicPublishInfoTable according to the Topic of the message. If not, it will be retrieved from NameServer and update to local cache, at the same time, Producer will retrieve routing information from NameServer every 30 seconds by default.
(2) When message Producer sends a message as a client, it needs to obtain routing information from the local cache TopicPublishInfoTable according to the Topic of the message. If not, it will be retrieved from NameServer and update to local cache, at the same time, Producer will retrieve routing information from NameServer every 30 seconds by default.
(3) Message producer Producer chooses a queue to send the message according to the routing information obtained in 2); Broker receives the message and records it in disk as the receiver of the message.
(4) After message consumer Consumer get the routing information according to 2) and complete the load balancing of the client, then select one or several message queues to pull messages and consume them.
