Pass response contexts from RPC middleware to HTTP middleware

[shunsukew]

I am developing a rate-limiting RPC middleware. Currently, jsonrpsee framework utilizes MethodResponse Extensions in the RPC layer and http::Response Extensions in the HTTP layer, with these extensions operating independently of each other.

I would like to propagate context information from the RPC layer to the HTTP layer to achieve functionality such as returning a status code other than 200 (429 in my case) or, at the very least, adding an HTTP header to indicate rate limiting based on data in contexts.

What would be the best approach to transfer context (Extensions) information from a jsonrpsee RPC middleware to a hyper HTTP middleware?

[niklasad1]

I think we could copy the extensions from the MethodResponse to the HTTP response to fix that and then you would need some HTTP middleware to check whether some error occurred and set desired HTTP status code on the response.

This shouldn't be that hard to fix

[shunsukew]

That would be really helpful. Thank you so much.
A single RPC call functions as expected, however, batch responses may require merging extension data. Addressing potential conflicts of the same Type data across calls within a batch is a subject for discussion.

[niklasad1]

Addressing potential conflicts of the same Type data across calls within a batch is a subject for discussion.

Yeah, that one is tricky because the Extensions works based on the rust type ids and it's not possible to merge two types in a clean way I think i.e, just overwrite them with the most recent one...

I had in mind that the user could inject a Vec or another collection that each call RPC call/request can push to it but we can't do that internally in jsonrpsee without some hacks like merging the rust collection types ourselves such as Vec<String>, Vec<usize> and so on...

For now, I don't have a good solution except make user responsible to "inject unique types" because it may be overwritten in a batch but annoying....

[shunsukew]

Thank you so much for updates.

I think overwriting is good practical options under the current situation.
One idea I have is jsonrpsee introduces new definition RpcExtensions and only insert this type to Http middleware extensions regardless whether it is single or batch, where RpcExtensions is a map of call id and AnyMap.

If users want to use AnyMap from jsonrpsee in hyper http layer, they can iterate over RpcExtensions.

[niklasad1]

One idea I have is jsonrpsee introduces new definition RpcExtensions and only insert this type to Http middleware extensions regardless whether it is single or batch, where RpcExtensions is a map of call id and AnyMap.

If users want to use AnyMap from jsonrpsee in hyper http layer, they can iterate over RpcExtensions.

Yes, that would work but I propose we go ahead with this simple approach first i.e, just overwrite but worth looking into replacing the http::Extensions for a nicer API for batches such for users to append to that collection instead of overwriting.

[shunsukew]

I agree. My implementation now depends on your PR branch and working good. Thank you so much