Clustering is a mode of synchronous replication between two or more nodes to implement fault tolerance to your system.
Vocera Platform is focused on supplying a system for the delivery of contextual alerts and alarms without any downtime. The database (DB) and voice clustering features provide high availability to support your system in the event of a hardware or software failure.
In Vocera Platform a cluster maintains a virtual IP address (VIP) that acts like a cluster-manager. The VIP is always assigned to the active (master) node. All external traffic is targeted at the VIP and routed to the active node, automatically.
Before configuring a node for clustering, you must choose whether to create a new cluster or to join an existing cluster. If you are creating a new cluster, then that node becomes the master of that cluster. If you are joining a node to an existing cluster, then that node becomes a standby (slave) in that cluster.
The active node of a cluster sends out heartbeat/keepalive messages to announce its presence to the other nodes in the cluster. If a standby node fails to receive any heartbeat messages within a predefined time interval (default is 15 seconds), then it promotes itself to become the master of the cluster.
In the event of a failure, the system must be able to recover and continue to process information. Vocera Platform uses an active-passive high availability (HA) model to continue processing information. In an active-passive HA model, all data on the active node is replicated to all passive (Slave, or Standby/Backup) nodes. When failover occurs, the new active node takes over the Virtual IP (VIP) address assigned to the cluster, switches the database out of replication mode, and activates all adapters.