alfresco-transform-core/docs/t-engines.md

T-Engines

The t-engines provide the basic transform operations. The Transform Service provides a common base for the communication with other components. It is this base that is described in this section. The base is a Spring Boot application to which transform specific code is added and then wrapped in a Docker image with any programs that the transforms need. The base does not need to be used as long as there appears to be a process responding endpoints and messages.

A t-engine groups together one of more Transformers. Each Transformer (provided by transform specific code) knows how to perform a set of transformations from one MIME Type to another with a common set of t-options.

0010 my-t-engine
  Transformer 1
    mimetype A -> mimetype B
    mimetype A -> mimetype C
    mimetype B -> mimetype C
    option1
    option2
  Transformer 2
    mimetype A -> mimetype B
    mimetype D -> mimetype C
    option2
    option3
0020 another-t-engine
  ...
0030 yet-another-t-engine
  ...

Endpoints

• POST /transform to perform a transform. There are two forms:
  • For asynchronous transforms: Perform a transform using a TransformRequest received from the t-router via a message queue. The TransformReply is sent back via the queue.
  • For synchronous transforms: Performs a transform on content uploaded as a Multipart File and provides the resulting content as a download. Transform options are extracted from the request properties. The following are not added as transform options, but are used to select the transformer: sourceMimetype & targetMimetype.
• GET /transform/config to obtain t-config about what the t-engine supports. It has a parameter configVersion to allow a caller and the t-engine to negotiate down to a common format. The value is an integer which indicate which elements may to be added to the config. These elements reflect functionality supported by the base (such as pre-signed URLs). The CoreVersionDecorator adds to the Config returned by the transform specific code.
• GET / provides an html test page to upload a source file, enter transform options and issue a synchronous transform request. Useful in testing.
• GET /log provides a page with basic log information. Useful in testing.
• GET /error provides an error page when testing.
• GET /version provides a String message to be included in client debug messages.
• GET /ready used by Kubernetes as a ready probe.
• GET /live used by Kubernetes as a ready probe.