common/download: resume test

common/download.go

@@ -99,8 +99,6 @@ func (d *DownloadClient) Cancel() {
 }
 
 func (d *DownloadClient) Get() (string, error) {
-	var f *os.File
-
 	// If we already have the file and it matches, then just return the target path.
 	if verify, _ := d.VerifyChecksum(d.config.TargetPath); verify {
 		log.Println("Initial checksum matched, no download needed.")
@@ -115,6 +113,7 @@ func (d *DownloadClient) Get() (string, error) {
 	log.Printf("Parsed URL: %#v", url)
 
 	// Files when we don't copy the file are special cased.
+	var f *os.File
 	var finalPath string
 	if url.Scheme == "file" && !d.config.CopyFile {
 		finalPath = url.Path
@@ -199,6 +198,15 @@ func (*HTTPDownloader) Cancel() {
 
 func (d *HTTPDownloader) Download(dst *os.File, src *url.URL) error {
 	log.Printf("Starting download: %s", src.String())
+
+	// Seek to the beginning by default
+	if _, err := dst.Seek(0, 0); err != nil {
+		return err
+	}
+
+	// Make the request. We first make a HEAD request so we can check
+	// if the server supports range queries. If the server/URL doesn't
+	// support HEAD requests, we just fall back to GET.
 	req, err := http.NewRequest("HEAD", src.String(), nil)
 	if err != nil {
 		return err
@@ -215,41 +223,21 @@ func (d *HTTPDownloader) Download(dst *os.File, src *url.URL) error {
 	}
 
 	resp, err := httpClient.Do(req)
-	if err != nil || resp.StatusCode != 200 {
-		req.Method = "GET"
-		resp, err = httpClient.Do(req)
-		if err != nil {
-			return err
-		}
-	}
-
-	if resp.StatusCode != 200 {
-		log.Printf(
-			"Non-200 status code: %d. Getting error body.", resp.StatusCode)
-		if req.Method != "GET" {
-			req.Method = "GET"
-			resp, err = httpClient.Do(req)
-			if err != nil {
-				return err
+	if err == nil && (resp.StatusCode >= 200 && resp.StatusCode < 300) {
+		// If the HEAD request succeeded, then attempt to set the range
+		// query if we can.
+		if resp.Header.Get("Accept-Ranges") == "bytes" {
+			if fi, err := dst.Stat(); err == nil {
+				if _, err = dst.Seek(0, os.SEEK_END); err == nil {
+					req.Header.Set("Range", fmt.Sprintf("bytes=%d-", fi.Size()))
+					d.progress = uint(fi.Size())
+				}
 			}
 		}
-		errorBody := new(bytes.Buffer)
-		io.Copy(errorBody, resp.Body)
-		return fmt.Errorf("HTTP error '%d'! Remote side responded:\n%s",
-			resp.StatusCode, errorBody.String())
 	}
 
+	// Set the request to GET now, and redo the query to download
 	req.Method = "GET"
-	d.progress = 0
-
-	if resp.Header.Get("Accept-Ranges") == "bytes" {
-		if fi, err := dst.Stat(); err == nil {
-			if _, err = dst.Seek(0, os.SEEK_END); err == nil {
-				req.Header.Set("Range", fmt.Sprintf("bytes=%d-", fi.Size()))
-				d.progress = uint(fi.Size())
-			}
-		}
-	}
 
 	resp, err = httpClient.Do(req)
 	if err != nil {
@@ -257,7 +245,6 @@ func (d *HTTPDownloader) Download(dst *os.File, src *url.URL) error {
 	}
 
 	d.total = uint(resp.ContentLength)
-
 	var buffer [4096]byte
 	for {
 		n, err := resp.Body.Read(buffer[:])

common/download_test.go

@@ -161,6 +161,41 @@ func TestDownloadClient_checksumNoDownload(t *testing.T) {
 	}
 }
 
+func TestDownloadClient_resume(t *testing.T) {
+	tf, _ := ioutil.TempFile("", "packer")
+	tf.Write([]byte("w"))
+	tf.Close()
+
+	ts := httptest.NewServer(http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
+		if r.Method == "HEAD" {
+			rw.Header().Set("Accept-Ranges", "bytes")
+			rw.WriteHeader(204)
+			return
+		}
+
+		http.ServeFile(rw, r, "./test-fixtures/root/basic.txt")
+	}))
+	defer ts.Close()
+
+	client := NewDownloadClient(&DownloadConfig{
+		Url:        ts.URL,
+		TargetPath: tf.Name(),
+	})
+	path, err := client.Get()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	raw, err := ioutil.ReadFile(path)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if string(raw) != "wello\n" {
+		t.Fatalf("bad: %s", string(raw))
+	}
+}
+
 func TestDownloadClient_usesDefaultUserAgent(t *testing.T) {
 	tf, err := ioutil.TempFile("", "packer")
 	if err != nil {