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V2 Endpoint

With the V2 REST API we started using a design driven process.

The API is defined using OpenAPI v2 in algod.oas2.json.

Updating the V2 REST API

  1. Document your changes by editing algod.oas2.json
  2. Regenerate the endpoints by running make generate.
  3. Update the implementation in server/v2/handlers.go. It is sometimes useful to consult generated/routes.go to make sure the handler properly implements ServerInterface.

What codegen tool is used?

We found that oapi-codegen produced the cleanest code, and had an easy to work with codebase. There is an algorand fork of this project which contains a couple modifications that were needed to properly support our needs.

Specifically, uint64 types aren't strictly supported by OpenAPI. So we added a type-mapping feature to oapi-codegen.

Why do we have algod.oas2.json and algod.oas3.yml?

We chose to maintain V2 and V3 versions of the spec because OpenAPI v3 doesn't seem to be widely supported. Some tools worked better with V3 and others with V2, so having both available has been useful. To reduce developer burdon, the v2 specfile is automatically converted v3 using converter.swagger.io.

Comments below are for v1 endpoints and are deprecated

Components:

  • swagger.json defines the API schema. However, server code in api/v1/... currently serves as the ground truth, as the schema is generated from server code.
    • to generate swagger.json, run make build. You may need to have go-swagger installed. You can get it by running make deps.
  • api/client is a package for internal (or external) libraries to interact with the REST API. In particular, it should minimize dependencies.
    • we currently use a non-swagger generated client. Why? The swagger generated client pulls in too many dependencies (go-openapi, for instance) and unnecessary functionality. Testing the swagger spec must be done another way. It seems that unwrapped json raw types are sent on the wire (so not wrapped by responses), so we don't need to decode them into responses.
  • api/v1/... contains an implementation for the server. The swagger schema is auto-generated (cd api/; swagger generate spec -o ./swagger.json) from server implementation code. api/v1/handlers and api/v1/models should never be directly imported by external clients.
    • or, run go generate in the api folder.

Debugging/Engineering Notes:

  • go-swagger does not generate x-nullable properties on model fields. We want them so that we can generate models without pointers. (This is more compatible with the current model we use. We may want to use pointers instead, eventually)
    • make sure you populate the default property in order to generate a model without a pointer field
  • go-swagger does not support OpenAPI 3.0. It only supports OpenAPI 2.0. There does not seem to be another tool that allows us to generate a swagger spec from code. It may be worth writing our own, eventually.
  • go-swagger does not support embedded structs.
    • in fact, go-swagger is generally very strange. The source -> spec generation looks fairly immature. Here are some (undocumented) tips:
      • every swagger:response type must contain a single field (e.g. Body or Payload) that is the actual data type you want to return. So the response type is a wrapper, which makes sense, except the clients that go-swagger generate automatically unwrap the underlying value. So this is very weird, and undocumented.
      • swagger:route is a less powerful version of the swagger:operation annotation. However, swagger:operation is much more finicky and not mature. When defining the annotation, make sure it is precise yaml, and start the yaml section with ---. This means keeping track of tabs and whitespaces. This seems to be the easiest way to define parameters without having to make explicit structs (which we may want to do eventually anyways).
  • don't deal with go-swagger codegen docs. Refer directly to https://github.com/OAI/OpenAPI-Specification/blob/master/versions/2.0.md#pathItemObject/
  • go-swagger does not support regex in path parameter path templating.
  • complex parameter schemas are only supported in parameters in:body
  • responses are distinct from definition objects (e.g. the former has adescription field, and headers). We always want to return a response in an operation. Returning a model seems to work, but does not seem advised.
  • go-swagger assumes x-isnullable: true and generates pointer files. If we ever want to use a swagger generated client internally this may be a problem. Note that go-swagger doesn't support a corresponding x-isnullable annotation. We can get around that by using the default annotation and then find-and-replacing an x-isnullable into the actual spec:
//go:generate sed -i "" -e "s/object\",/object\", \"x-nullable\": false,/" ./swagger.json
  • go-swagger does not seem to support simple string responses. They always get wrapped. (oh well) e.g. [go-swagger/go-swagger#1635]
  • I've hardcoded a keylength into the spec for now, until I figure out how to tie that programatically back into the server code (perhaps with a find-and-replace).