The DDE consists of the 4 following components:
· Translation Servlet
The Translation Servlet is a Java servlet specifically used by DDE. It forwards the translation request from the client on to the QServer for processing. It then returns the successful translation results back to the client.
The QServer is a stand alone Java application that queues the requests sent from the Translation Servlet and sends them on to available FME Servers. If an FME Server is busy, the QServer queues the requests until the FME Server becomes available again. If multiple FME Servers are registered, the QServer is responsible for selective load distribution.
· FME Server
The FME Server performs the requested translations and informs the Translation Servlet that the compressed translation results are available for subsequent download by the user. It registers with the QServer, indicating that it is available to perform translations. The FME Server then establishes and maintains a network connection with the QServer and performs translations requests as they arise.
· Process Monitor
The Process Monitor is a stand alone Java application that starts the other DDE components and automatically restarts them if they terminate for any reason. This enables a degree of fault tolerance to be built into the system.