Reusing http connections in Golang

Question

I\'m currently struggling to find a way to reuse connections when making HTTP posts in Golang.

I\'ve created a transport and client like so:

// Crea         


        

Answer 1

Edit: This is more of a note for people that construct a Transport and Client for every request.

Edit2: Changed link to godoc.

Transport is the struct that holds connections for re-use; see https://godoc.org/net/http#Transport ("By default, Transport caches connections for future re-use.")

So if you create a new Transport for each request, it will create new connections each time. In this case the solution is to share the one Transport instance between clients.

Answer 2

Another approach to init() is to use a singleton method to get the http client. By using sync.Once you can be sure that only one instance will be used on all your requests.

var (
    once              sync.Once
    netClient         *http.Client
)

func newNetClient() *http.Client {
    once.Do(func() {
        var netTransport = &http.Transport{
            Dial: (&net.Dialer{
                Timeout: 2 * time.Second,
            }).Dial,
            TLSHandshakeTimeout: 2 * time.Second,
        }
        netClient = &http.Client{
            Timeout:   time.Second * 2,
            Transport: netTransport,
        }
    })

    return netClient
}

func yourFunc(){
    URL := "local.dev"
    req, err := http.NewRequest("POST", URL, nil)
    response, err := newNetClient().Do(req)
    // ...
}

Answer 3

Ensure that you read until the response is complete AND call Close().

e.g.

res, _ := client.Do(req)
io.Copy(ioutil.Discard, res.Body)
res.Body.Close()

Again... To ensure http.Client connection reuse be sure to:

• Read until Response is complete (i.e. ioutil.ReadAll(resp.Body))
• Call Body.Close()