path: root/rpc/http.go

// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package rpc

import (
    "bytes"
    "encoding/json"
    "fmt"
    "io"
    "io/ioutil"
    "net/http"
    "net/url"
    "strings"

    "github.com/rs/cors"
)

const (
    maxHTTPRequestContentLength = 1024 * 128
)

// httpClient connects to a geth RPC server over HTTP.
type httpClient struct {
    endpoint   *url.URL    // HTTP-RPC server endpoint
    httpClient http.Client // reuse connection
    lastRes    []byte      // HTTP requests are synchronous, store last response
}

// NewHTTPClient create a new RPC clients that connection to a geth RPC server
// over HTTP.
func NewHTTPClient(endpoint string) (Client, error) {
    url, err := url.Parse(endpoint)
    if err != nil {
        return nil, err
    }
    return &httpClient{endpoint: url}, nil
}

// Send will serialize the given msg to JSON and sends it to the RPC server.
// Since HTTP is synchronous the response is stored until Recv is called.
func (client *httpClient) Send(msg interface{}) error {
    var body []byte
    var err error

    client.lastRes = nil
    if body, err = json.Marshal(msg); err != nil {
        return err
    }

    resp, err := client.httpClient.Post(client.endpoint.String(), "application/json", bytes.NewReader(body))
    if err != nil {
        return err
    }

    defer resp.Body.Close()
    if resp.StatusCode == http.StatusOK {
        client.lastRes, err = ioutil.ReadAll(resp.Body)
        return err
    }

    return fmt.Errorf("request failed: %s", resp.Status)
}

// Recv will try to deserialize the last received response into the given msg.
func (client *httpClient) Recv(msg interface{}) error {
    return json.Unmarshal(client.lastRes, &msg)
}

// Close is not necessary for httpClient
func (client *httpClient) Close() {
}

// SupportedModules will return the collection of offered RPC modules.
func (client *httpClient) SupportedModules() (map[string]string, error) {
    return SupportedModules(client)
}

// httpReadWriteNopCloser wraps a io.Reader and io.Writer with a NOP Close method.
type httpReadWriteNopCloser struct {
    io.Reader
    io.Writer
}

// Close does nothing and returns always nil
func (t *httpReadWriteNopCloser) Close() error {
    return nil
}

// newJSONHTTPHandler creates a HTTP handler that will parse incoming JSON requests,
// send the request to the given API provider and sends the response back to the caller.
func newJSONHTTPHandler(srv *Server) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        if r.ContentLength > maxHTTPRequestContentLength {
            http.Error(w,
                fmt.Sprintf("content length too large (%d>%d)", r.ContentLength, maxHTTPRequestContentLength),
                http.StatusRequestEntityTooLarge)
            return
        }

        w.Header().Set("content-type", "application/json")

        // create a codec that reads direct from the request body until
        // EOF and writes the response to w and order the server to process
        // a single request.
        codec := NewJSONCodec(&httpReadWriteNopCloser{r.Body, w})
        defer codec.Close()
        srv.ServeSingleRequest(codec, OptionMethodInvocation)
    }
}

// NewHTTPServer creates a new HTTP RPC server around an API provider.
func NewHTTPServer(corsString string, srv *Server) *http.Server {
    var allowedOrigins []string
    for _, domain := range strings.Split(corsString, ",") {
        allowedOrigins = append(allowedOrigins, strings.TrimSpace(domain))
    }

    c := cors.New(cors.Options{
        AllowedOrigins: allowedOrigins,
        AllowedMethods: []string{"POST", "GET"},
    })

    handler := c.Handler(newJSONHTTPHandler(srv))

    return &http.Server{
        Handler: handler,
    }
}