PrepServer Architecture

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This is an overview of the complete PrepServer system. The client communicates with the front-end (PrepServer Front-End), which is connected to the middle-tier (PrepServer Management Service). This Management Service distributes the client pre-processing requests among the available PrepServer IDL Pre-Processors (back-end).

The PrepServer is a Java server application that allows for remote pre-processing of solar data. It currently pre-processes the following instruments:

The PrepServer is a three tier server application:

Web Front-End

The Web Front-End is a Java web application running in a Tomcat. The service specification is available on Hesperia and Wilco in form of a WSDL file.

The Web Front-End has two main responsibilities:

Management Service

This schema shows the Management Service architecture and how pre-processing requests are handled by it (distribution among idle Pre-Processing Services).

The Management Service is the intermediary between the Web Front-End and the Pre-Processing Services and is a separate service independent of the other components. It's main responsibilities are:

Pre-processing Service

Pre-processing Servers are SSW IDL enabled services that perform the actual pre-processing in SSW IDL.

Pre-processing usually involves the following steps:

  1. Reading the pre-processing requests that are modeled in Java and converting them to an IDL readable set of parameters.
  2. Downloading the un-processed data using the Media Service.
  3. Sending the data file and all parameters to SSW IDL and invoking the appropriate pre-processing routines.
  4. After the successful completion, uploading the now pre-processed data to the Web Front-End (again by using the Media Service).
  5. Freeing the server and make it available to new requests.

Pre-processing Servers all maintain their own IDL session (idl_opserver) and are therefore independent from one another. This allows for multiple pre-processing servers on the same machine, each occupying another CPU. Should more processing power be needed, pre-processing servers can be started on distributed machines and configured to register with an already available centralized Management Service.

Pre-processing Servers register at startup with the Management Service and un-register upon receiving a termination signal. They do AFTER completing their current pre-processing requests.

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