Cluster

In EMQX, cluster is a group of EMQX nodes that work together to provide a highly scalable and fault-tolerant MQTT messaging system. Clustering allows you to distribute the load across multiple nodes and ensure that the system can continue to operate even if one or more nodes fail.

Node Names

Before starting the cluster creation step, let’s first get familiar with the concept of node names in EMQX. EMQX nodes are identified by their names. A node name consists of two parts, node name and host, separated with @, for example, emqx@s1.emqx.io. The host part must either be the IP address or a fully qualified domain name (FQDN), such as myhost.example.tld, for instance:

• For EMQX node deployed on server s1.emqx.io, the node name should be emqx@s1.emqx.io;
• If this server has a static IP (192.168.0.10), the node name should be emqx@192.168.0.10.

When configuring nodes with emqx.conf, you can work with the code below:

node {
  name = "emqx@s1.emqx.io"
  role = core
}

Where,

• name refers to the desired node name, for example, emqx@localhost.
• role refers to the function that EMQX node performs within an EMQX cluster. There are 2 types of roles: core nodes and replicant codes. For a detailed explanation of core nodes and replicant nodes, see EMQX Clustering - Core and Replicant Nodes.
  • default value: core
  • optional value: core or replicant

Configure Cluster

In EMQX, cluster is a group of EMQX nodes that work together to provide a highly scalable and fault-tolerant MQTT messaging system. Clustering allows you to distribute the load across multiple nodes and ensure that the system can continue to operate even if one or more nodes fail.

This section introduces how to configure an EMQX cluster. You can add the cluster configuration items either on a core or replicant node, if you are working on a replicant node, there are severl but some configuration items, for example, core_nodes, only take effect under certain preconditions:

• node.db_backend of the node is set to rlog, indicating the node uses rlog as the database backend.
• node.role is set to replicant, indicating this code functions as a replicant node.
• node.discovery_strategy is set to manual or static, there is no need to set this configuration item if automatic cluster discovery mechanism is used. For a detailed explanation of the node discovery strategy and the corresponding configuration items, see Create Cluster.

cluster {
  name = emqxcl
  discovery_strategy = manual
  core_nodes = []
  driver = tcp
  ssl_options {
    certfile = ""
    keyfile = ""
    cacertfile = ""
  }
}

Where,

TIP

EMQX has offered more configuration items to better serve customized needs, you can continue to read Configuration Manual.