A description of the High Availability configuration for Managers within Sybase CEP Server clusters, as well as their general functionality.
A Sybase CEP Server cluster configured for Manager HA includes one active or primary Manager and one or more passive Managers. If the active Manager fails, one of the passive Managers becomes active. Managers within a Sybase CEP Server cluster communicate with one another by writing information to and reading information from a common directory, specified in the "StoragePath" preference. Two of the HA-specific files that reside in this directory are mgr_primary_node and mgr_heartbeat. The mgr_primary_node file indicates which Manager is currently functioning as the primary. The mgr_heartbeat file records the primary Manager's heartbeat (which you set with the "HeartbeatFrequencySeconds" preference in the c8-manager-cluster.xml file.)
Sybase CEP Server uses this heartbeat to determine whether or not the primary Manager is available and running properly. If the primary Manager fails, the other Managers in the Cluster detect that the Manager's heartbeat has stopped and initiate the selection of a new primary Manager.
Since the new primary Manager has a different IP address from the original Manager, the new primary Manager must "announce" itself to all the Containers in the Server Cluster, to make sure that communications intended for the Manager are routed to the right destination. To avoid the need to notify each individual Container, whenever a new Manager is activated, the Sybase system relies on a dynamic Domain Name Service (DNS) to route messages from the Containers to the current active Manager.
Containers send messages to a generic Manager hostname. The DNS server then translates the hostname to the IP address of the current active Manager. In the event of Manager failover, the new primary Manager notifies the DNS server that the generic host name should now point to the new Manager's IP address. In order for Manager HA features to work correctly, the DNS server must be running continuously and must be accessible to all Managers and Containers.
Note, however, that the DNS does not translate port numbers. Since Containers in a Sybase CEP Server cluster are configured for a specific Manager port, all Managers in the Cluster must use the same port.