Using the Event Monitoring Service (June 2007)

Understanding the Event Monitoring Service
EMS Framework Components
Chapter 1 25
The registrar does not need to keep any state information and does not
need to be highly available. It does not need to be running while a
resource is being monitored. The registrar is needed only to start the
monitors and to provide communication between clients and monitors.
One registrar process is started each time a client application calls
rm_client_connect(), so a registrar is always connected to one client.
Depending on the requests sent by the client, the registrar may be
connected to 0, 1, 2, or more resource monitors concurrently. The
information in the messages contain enough information to allow the
registrar to route the requests and replies correctly.
Figure 1-3 illustrates how connections are made between clients and
registrars.
Figure 1-3 Connections Among Clients and registrars
Each time the registrar starts, it reads the resource dictionary,
exchanges internal version information with the client application, and
prepares to receive client requests. When a request arrives, the registrar
analyzes it to determine if it is one that it can reply to, or whether it
needs to pass the request to a resource monitor.