Using the Event Monitoring Service (November 1999)

Chapter 1 25
Understanding the Event Monitoring Service
EMS Framework Components
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 contains enough information to allow the
registrar to route the requests and replies correctly.
Figure 1-3 gives an example of what kinds of connections are possible.
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.
When the registrar needs to pass the request to a resource monitor, it
needs to determine if the resource monitor is currently running. If the
appropriate resource monitor process is not found, the registrar starts
the process and waits until the resource monitor can communicate with
the registrar.