The Symphony service-oriented middleware components consist of the Session Director, session manager(s), service instance managers, and service instances.
The following diagram shows the components and interactions between them.
There is one Session Director in a Symphony cluster. It is started as an EGO system service.
There may be a single session manager, or multiple session managers in a Symphony cluster. The number of session managers depends on the number of running applications. A session manager is created upon the first user connection to an application for which no session manager exists, or it may be configured to prestart even if there is no workload.
Routes task input and output messages between the client application and compute hosts
Schedules sessions based on various scheduling policies (proportional, minimum service, and so on)
Provides fault-tolerant message handling as specified by the application profile
Manages the life cycle of service instance managers, and manages the interaction with the resource manager
There is one service instance manager for every instantiation of a service. A service instance manager is created and destroyed by the session manager.