Comment by kentonv

Comment by kentonv 11 hours ago

The Cache API is a web-standard API. We chose to follow it in an attempt to follow standards. Unfortunately it turned out to be a poor fit. Among other things, as you note, the "cache key" is required to be HTTP-request-shaped, but must be a GET request, so to cache the result of a POST request you have to create a fake GET request that encodes the unique cache key in the URL. The keys should have just been strings computed by the app all along, but that's not what the standard says.

We'll likely replace it at some point with a non-standard API that works better. People will then accuse us of trying to create lock-in. ¯\_(ツ)_/¯

locknitpicker 9 hours ago

> The Cache API is a web-standard API. We chose to follow it in an attempt to follow standards.

That's perfectly fine, but it doesn't justify the lack of support for non-GET requests though. The Cache API represents the interface but you dictate what you choose how to implement it. In fact, Cloudflare's cache API docs feature some remarks on how Cloudflare chose to implement some details a certain way and chose to not implement at all some parts of Cache API.

https://developers.cloudflare.com/workers/runtime-apis/cache...

Also, the Cache API specification doesn't exclude support for non-GET requests.

https://w3c.github.io/ServiceWorker/#cache-put

If Cloudflare's Cache API implementation suddenly supported POST requests, the only observable behavior change would be that cache.put() would no longer throw an error for requests other than GET. This is hardly an unacceptable change.

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kentonv 8 hours ago

We can't implement automatic caching of POST requests because there is no standard for computing cache keys for POST requests; it's different for every application.
E.g. presumably the body of the request matters for cache matching, but the body can be any arbitrary format the application chooses. The platform has no idea how to normalize it to compute a consistent cache key -- except perhaps to match the whole body byte-for-byte, but for many apps that would not produce the desired behavior. For example, if you had a trace ID in your requests, now none of your requests would hit cache because each one has a unique trace ID, but of course a trace ID is not intended to be considered for caching.
The Cache API can only implement the semantics that the HTTP standard specifies for caching, and the HTTP standard does not specify any semantics for caching POST requests.
That said, what we really should have done was left it up to the application to compute cache keys however they want, and only implemented the lookup from string cache key -> Response object. That's not what the standard says, though.

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