Why does progressToken exist?

[LeeSaferite]

Pre-submission Checklist

• I have checked that this question would not be more appropriate as an issue in a specific repository
• I have searched existing discussions and documentation for answers

Question Category

• Protocol Specification
• SDK Usage
• Server Implementation
• General Implementation
• Documentation
• Other

Your Question

Working through the specification and the concept of a progressToken is confusing me. Mechanically I fully understand it and how to use it. My confusion relates to why it's even a distinct thing. It's only relevant when sending a Request, has to be unique across all Active Requests, and there's only one per Request. Why not simply use requestId and a flag in _meta indicating a desire to receive progress tracking? A requestId has stricter requirements and there's already precedent in the spec for using requestId in a notification with request cancellations. As it is, it's adding an extra level of tracking/routing where I have to match up the incoming notification to a request by that progressToken instead of simply by the requestId. It's extra complexity for no obvious reason.

Now that I have understood this, I'll simply be using requestId as a progressToken in my code. It'll make the Requestor code simpler as they don't need a more complicated lookup to route progress notifications. Obviously I can't do anything about the Processor code unless the spec gets updated in the future.