etcd-io__etcd/client/http.go

/*
   Copyright 2014 CoreOS, Inc.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

package client

import (
	"io/ioutil"
	"net/http"
	"net/url"
	"time"

	"github.com/coreos/etcd/Godeps/_workspace/src/code.google.com/p/go.net/context"
)

var (
	ErrTimeout            = context.DeadlineExceeded
	DefaultRequestTimeout = 5 * time.Second
)

// transport mimics http.Transport to provide an interface which can be
// substituted for testing (since the RoundTripper interface alone does not
// require the CancelRequest method)
type transport interface {
	http.RoundTripper
	CancelRequest(req *http.Request)
}

type httpAction interface {
	httpRequest(url.URL) *http.Request
}

type roundTripResponse struct {
	resp *http.Response
	err  error
}

type httpClient struct {
	transport transport
	endpoint  url.URL
	timeout   time.Duration
}

func newHTTPClient(tr *http.Transport, ep string, to time.Duration) (*httpClient, error) {
	u, err := url.Parse(ep)
	if err != nil {
		return nil, err
	}

	c := &httpClient{
		transport: tr,
		endpoint:  *u,
		timeout:   to,
	}

	return c, nil
}

func (c *httpClient) doWithTimeout(act httpAction) (*http.Response, []byte, error) {
	ctx, cancel := context.WithTimeout(context.Background(), c.timeout)
	defer cancel()
	return c.do(ctx, act)
}

func (c *httpClient) do(ctx context.Context, act httpAction) (*http.Response, []byte, error) {
	req := act.httpRequest(c.endpoint)

	rtchan := make(chan roundTripResponse, 1)
	go func() {
		resp, err := c.transport.RoundTrip(req)
		rtchan <- roundTripResponse{resp: resp, err: err}
		close(rtchan)
	}()

	var resp *http.Response
	var err error

	select {
	case rtresp := <-rtchan:
		resp, err = rtresp.resp, rtresp.err
	case <-ctx.Done():
		c.transport.CancelRequest(req)
		// wait for request to actually exit before continuing
		<-rtchan
		err = ctx.Err()
	}

	// always check for resp nil-ness to deal with possible
	// race conditions between channels above
	defer func() {
		if resp != nil {
			resp.Body.Close()
		}
	}()

	if err != nil {
		return nil, nil, err
	}

	body, err := ioutil.ReadAll(resp.Body)
	return resp, body, err
}