The following terms are used throughout the discussions of and instructions for DMR.
- A DMR node is one of the following:
- a single software event broker
- a High Availability (HA) group of software event brokers
- a single appliance
- an HA (active / standby) pair of appliances
- an event broker service in PubSub+ Cloud
That is, a node can be composed of just one event broker, or several event brokers if redundancy is configured.
If replication is configured for a node, its replication mate is considered a separate node
(see Using Replication with DMR for more information).
- Gateway Node
- A node that has an external link to a node in another cluster.
- A customer application that connects to a node.
- A link is relationship between nodes. It is made up of the TCP connections that transmit topology information, subscriptions, and data.
- A channel is connection within a link. Each link has the following channels:
- a single control channel that carries topology and subscription-control messages
- one data channel per message VPN that carries client data messages
- Internal Link
- A link that spans from one node to another within the same cluster is called an internal link. Internal links connect nodes together so that messages published to one node can be received by a consumer connected to another node.
- External Link
- A link that spans from a node in one cluster to a node in another cluster is called an external link. External links join gateway nodes of different clusters together, which allows messages published in one cluster to be delivered to consumers in another cluster.
- A set of nodes connected by internal links. Messages published to any node in the cluster are delivered to clients attached to any other node in the cluster. Each cluster may be as simple as a single node, or contain as many as 15 nodes connected by internal links.
- Event Mesh
- A set of clusters connected by external links. Messages published to any cluster in the network are delivered to clients attached to any other directly connected cluster in the network. These clusters are usually geographically or logically dispersed. An event mesh is also referred to as a network.
- A topology is a specific arrangement of links between nodes in a network (or event mesh). An internal topology is defined by its internal links (within a cluster). An external topology is defined by its external links (between clusters).