rpc

Documentation

Overview

HTTP RPC server supporting calls via uri params, jsonrpc over HTTP, and jsonrpc over websockets

Client Requests

Suppose we want to expose the rpc function `HelloWorld(name string, num int)`.

GET (URI)

As a GET request, it would have URI encoded parameters, and look like:

curl 'http://localhost:8008/hello_world?name="my_world"&num=5'

Note the `'` around the url, which is just so bash doesn't ignore the quotes in `"my_world"`. This should also work:

curl http://localhost:8008/hello_world?name=\"my_world\"&num=5

A GET request to `/` returns a list of available endpoints. For those which take arguments, the arguments will be listed in order, with `_` where the actual value should be.

POST (JSONRPC)

As a POST request, we use JSONRPC. For instance, the same request would have this as the body:

{
  "jsonrpc": "2.0",
  "id": "anything",
  "method": "hello_world",
  "params": {
    "name": "my_world",
    "num": 5
  }
}

With the above saved in file `data.json`, we can make the request with

curl --data @data.json http://localhost:8008

WebSocket (JSONRPC)

All requests are exposed over websocket in the same form as the POST JSONRPC. Websocket connections are available at their own endpoint, typically `/websocket`, though this is configurable when starting the server.

Server Definition

Define some types and routes:

type ResultStatus struct {
	    Value string
}

Define some routes

  var Routes = map[string]*rpcserver.RPCFunc{
	    "status": rpcserver.NewRPCFunc(Status, "arg"),
  }

An rpc function:

  func Status(v string) (*ResultStatus, error) {
	    return &ResultStatus{v}, nil
  }

Now start the server:

mux := http.NewServeMux()
rpcserver.RegisterRPCFuncs(mux, Routes)
wm := rpcserver.NewWebsocketManager(Routes)
mux.HandleFunc("/websocket", wm.WebsocketHandler)
logger := log.NewTMLogger(log.NewSyncWriter(os.Stdout))
listener, err := rpc.Listen("0.0.0.0:8080", rpcserver.Config{})
if err != nil { panic(err) }
go rpcserver.StartHTTPServer(listener, mux, logger)

Note that unix sockets are supported as well (eg. `/path/to/socket` instead of `0.0.0.0:8008`) Now see all available endpoints by sending a GET request to `0.0.0.0:8008`. Each route is available as a GET request, as a JSONRPCv2 POST request, and via JSONRPCv2 over websockets.

Examples

- [Tendermint](https://github.com/tendermint/tendermint/blob/master/rpc/core/routes.go)