The Global Namespace feature enables Workflow Executions to progress through another Cluster in the event of a failover.
A Global Namespace may be replicated to any number of Clusters, but is active in only one Cluster at any given time.
For a failover to be successful, Worker Processes must be polling for Tasks for the Global Namespace on all Clusters.
A Global Namespace has a failover version. Because a failover can be triggered from any Cluster, the failover version prevents certain conflicts from occurring if a failover is mistakenly triggered simultaneously on two Clusters.
Only the active Cluster dispatches Tasks; however, certain conflicts are possible. Unlike regular Namespaces, which provide at-most-once semantics for an Activity Execution, Global Namespaces can support only at-least-once semantics (see Conflict resolution). Worker Processes on the standby Clusters are idle until a failover occurs and their Cluster becomes active.
Temporal Application API calls made to a non-active Cluster are rejected with a NamespaceNotActiveError which contains the name of the current active Cluster. It is the responsibility of the Temporal Application to call the Cluster that is currently active.