Support Github actions cache API backend (feature request)

[itsbalamurali]

It would be great if the project can add support for the GitHub actions cache API backend, which would make it usable on Github actions without needing an external remote caching server.

Docs: https://github.com/tonistiigi/go-actions-cache/blob/master/api.md

[cerupcat]

Any movement on this or ideas on how we can help get this up and running?

[polac24]

I looked again on that idea and seems that it would be quite easy to implement it, even the exposed API is a bit weird.

My ideas is that you create a new implementation of the NetworkClient protocol: https://github.com/spotify/XCRemoteCache/blob/b439674378a29d4d2bafd0983f851e0f0f2c630a/Sources/XCRemoteCache/Network/NetworkClient.swift#L37-L43

As a starting point, CachedNetworkClient could be a good example to see how to implement the composite that uses a different underlying API. So you would need to create an adapter.

Here is a sketchy pseudo-code:

 class GitHubActionCacheNetworkClient { 
 init(urlTranslator: GitHubActionCacheURLTranslator, networkClient: NetworkClien){
///
}
     func fileExists(_ url: URL, completion: @escaping (Result<Bool, NetworkClientError>) -> Void)  {
   let translatedUrl = urlTranslator.translate(url: url)
   networkClient.fetch(translatedUrl) {
      // if .success -> call completion(true)
    }
    }
     func fetch(_ url: URL, completion: @escaping (Result<Data, NetworkClientError>) -> Void){
      let translatedUrl = urlTranslator.translate(url: url)
       networkClient.fetch(translatedUrl) { result
           // if success
           networkClient.fetch(result.archiveLocation, completion: completion)
       }
     }
     func download(_ url: URL, to location: URL, completion: @escaping (Result<Void, NetworkClientError>) -> Void) {
      let translatedUrl = urlTranslator.translate(url: url)
       networkClient.fetch(translatedUrl, completion: completion)
       networkClient.fetch(translatedUrl) { result
           // if success
           networkClient.download(result.archiveLocation, to: location, completion: completion)
       }
     }
     func upload(_ file: URL, as url: URL, completion: @escaping (Result<Data, NetworkClientError>) -> Void) {
           let translatedUrl = urlTranslator.translate(url: url)
           // Some kind of a hack - store the request body to a file
          file.write(JSONSerializer....)
           networkClient.upload(file, as:translatedUrl) { result in
              // if success
              // networkClient doesn't have PATCH, so that would need to be added 
              networkClient.patch(result.location) { result2 in
                /// if success
                networkClient.post(result.location, completion: completion)
              }
           }
     }
     /// Creates an empty file at the remote location 
     func create(_ url: URL, completion: @escaping (Result<Void, NetworkClientError>) -> Void)  {
         let translatedUrl = urlTranslator.translate(url: url)
          // Some kind of a hack - store the request body to a file
          file.write(JSONSerializer....)
         networkClient.upload(translatedUrl) { result in
              // if success
              // Warning: networkClient doesn't have PATCH, so that would need to be added 
              networkClient.upload(file) {
                // if success
                   networkClient.create(result.location, completion: completion)
               }
           }
    }

To implement the above, one new method and one modification to NetworkClient would be required:

• Change: func upload(_ file: URL, as url: URL, completion: @escaping (Result<Void, NetworkClientError>) -> Void) -> func upload(_ file: URL, as url: URL, completion: @escaping (Result<Data, NetworkClientError>) -> Void)
• New method (here would be the PATCH request used): func override(_ file: URL, as url: URL, completion: @escaping (Result<Data, NetworkClientError>) -> Void)

Notes:

• The authentication part doesn't need any changes: XCRemoteCache already has request_custom_headers config that could be used for that.
• Switching between standard (nginx-like API) and GitHubActions could be controlled by a new property in .rcinfo so that change can be definitely upstreamed to the main repo (now spotify/XCRemoteCache)
• Right now, I am not aware that anyone is working on that, contribution is welcome

[cerupcat]

Thanks @polac24, that's helpful. I'll look into it a bit.

[cerupcat]

I wasn't able to get anywhere with this. Anyone have bandwidth on getting this working if it's low lift?