Golang HTTP POST成功，但未调用docker操作

Question

Problem: Although I can easily issue GET and POST commands from curl on my local docker socket, when I try to do the POST equivalent in Golang for a docker pull action, using net.Dial, I see no action taken on Docker's behalf.

Note that, meanwhile, the GET action works just fine using docker sockets via the golang client.

For example, when running the code at the bottom of this post, I see:

2018/01/05 14:16:33 Pulling http://localhost/v1.24/images/create?fromImage=fedora&tag=latest ......
2018/01/05 14:16:34 Succeeded pull for http://localhost/v1.24/images/create?fromImage=fedora&tag=latest &{200 OK 200 HTTP/1.1 1 1 map[Docker-Experimental:[true] Ostype:[linux] Server:[Docker/17.09.0-ce (linux)] Api-Version:[1.32] Content-Type:[application/json] Date:[Fri, 05 Jan 2018 19:16:34 GMT]] 0xc42010a100 -1 [chunked] false false map[] 0xc420102000 <nil>}

The code for attempting to do a pull via a POST action:

// pullImage is the equivalent of curl --unix-socket /var/run/docker.sock -X POST http://localhost/images/create?fromImage=alpine
func pullImage(img string, tag string) (err error) {
        fd := func (proto, addr string) (conn net.Conn, err error) {
                return net.Dial("unix", "/var/run/docker.sock")
        }
        tr := &http.Transport{
                Dial: fd,
        }
        client := &http.Client{Transport: tr}
        imageUrl := fmt.Sprintf("http://localhost/v1.24/images/create?fromImage=%s&tag=%s", img, tag)
        log.Printf("Pulling %s ......  ", imageUrl)
        resp, err := client.Post(imageUrl, "application/json", nil)
        if resp.StatusCode == 200 && err == nil {
                log.Printf("Succeeded pull for %s %v",imageUrl, resp)
        } else {
                log.Printf("FAILED pull for %s , ERROR = ((  %s  )) ",imageUrl , err)
        }
        return err

Question:

What does curl --unix-socket /var/run/docker.sock -X POST http://localhost/v1.24/images/create?fromImage=fedora do differently then the Golang code in the above snippet?

Answer 1

I figured this out. Actually, my prolem was that I wasn't completing the response body.

Adding

defer resp.Body.Close()

after the rest, err := client... clause was enough to finish triggering an entire pull. Not quite sure why closing the response body effects the ability of docker to start pulling the images down, but in any case, that was the case.