// send sends a request, kills it after passed timeout and writes the result to passed channel
func send(httpClient *http.Client, tr *http.Transport, req request, timeout time.Duration, resp chan request) {
if *debug {
fmt.Println("Sending a request to", req.httpReq.URL)
}
// Send the HTTP request in it's own goroutine using a HTTP client to be able to abort the request if reached timeout
go func() {
start := time.Now()
resp, err := httpClient.Do(req.httpReq)
if err != nil {
req.err = err
} else {
req.StatusCode = resp.StatusCode
req.Duration = time.Since(start)
resp.Body.Close()
}
// Indicate the request is finished
close(req.done)
}()
// Either the request finished, or the timeout triggers
select {
case <-req.done:
// Request is done, please continue
case <-time.After(timeout):
req.Duration = timeout
// Manually cancel the request in flight
tr.CancelRequest(req.httpReq)
req.err = errTimeout
}
// Send back on the response channel
resp <- req
}
func Fanout(transport *http.Transport, request *http.Request, endpoints []*Endpoint) (*http.Response, error) {
body, err := ioutil.ReadAll(request.Body)
if err != nil {
return nil, err
}
responses := make(chan *http.Response, len(endpoints))
errs := make(chan error, len(endpoints))
for _, e := range endpoints {
url := *request.URL
url.Scheme = "http"
url.Host = e.Addr
req := *request
req.Body = ioutil.NopCloser(bytes.NewBuffer(body))
req.URL = &url
req.Close = true
request := &req
go func() {
response, err := transport.RoundTrip(request)
if err != nil {
errs <- err
} else {
responses <- response
}
}()
defer transport.CancelRequest(request)
}
var fanoutErr error
var response *http.Response
for i := 0; i < len(endpoints); i++ {
select {
case fanoutErr = <-errs:
case response = <-responses:
if response.StatusCode < 400 {
return response, nil
}
}
}
if response != nil {
return response, nil
}
return nil, fanoutErr
}
// HTTPDo runs the HTTP request in a goroutine and passes the response to f in
// that same goroutine. After the goroutine finishes, returns the result of f.
// If ctx.Done() receives before f returns, calls transport.CancelRequest(req) before
// before returning. Even though HTTPDo executes f in another goroutine, you
// can treat it as a synchronous call to f. Also, since HTTPDo uses client to run
// requests and transport to cancel them, client.Transport should be transport
// in most cases.
//
// Example Usage:
// type Resp struct { Num int `json:"num"` }
// var resp *Resp
// err := HttpDo(ctx, client, transport, req, func(resp *http.Response, err error) error {
// if err != nil { return err }
// defer resp.Body.Close()
//
// if err := json.NewDecoder(resp.Body).Decode(resp); err != nil {
// return err
// }
// return nil
// })
// if err != nil { return err }
// // do something with resp...
//
// This func was stolen/adapted from https://blog.golang.org/context
func HTTPDo(ctx context.Context, client *http.Client, transport *http.Transport, req *http.Request, f func(*http.Response, error) error) error {
// Run the HTTP request in a goroutine and pass the response to f.
c := make(chan error, 1)
// see if the ctx was already cancelled/timed out
select {
case <-ctx.Done():
return ErrCancelled
default:
}
go func() {
c <- f(client.Do(req))
}()
select {
case <-ctx.Done():
transport.CancelRequest(req)
<-c // Wait for f to return.
return ctx.Err()
case err := <-c:
return err
}
}