improve remote image rendering (#13102)

* improve remote image rendering

- determine "domain" during Init() so we are not re-parsing settings
  on every request
- if using http-mode via a rednererUrl, then use the AppUrl for the
  page that the renderer loads.  When in http-mode the renderer is likely
  running on another server so trying to use the localhost or even the
  specific IP:PORT grafana is listening on wont work.
- apply the request timeout via a context rather then directly on the http client.
- use a global http client so we can take advantage of connection re-use
- log and handle errors better.

* ensure imagesDir exists

* allow users to define callback_url for remote rendering

- allow users to define the url that a remote rendering service
  should use for connecting back to the grafana instance.
  By default the "root_url" is used.

* improve remote image rendering

- determine "domain" during Init() so we are not re-parsing settings
  on every request
- if using http-mode via a rednererUrl, then use the AppUrl for the
  page that the renderer loads.  When in http-mode the renderer is likely
  running on another server so trying to use the localhost or even the
  specific IP:PORT grafana is listening on wont work.
- apply the request timeout via a context rather then directly on the http client.
- use a global http client so we can take advantage of connection re-use
- log and handle errors better.

* ensure imagesDir exists

* allow users to define callback_url for remote rendering

- allow users to define the url that a remote rendering service
  should use for connecting back to the grafana instance.
  By default the "root_url" is used.

* rendering: fixed issue with renderKey where userId and orgId was in mixed up, added test for RenderCallbackUrl reading logic

pkg/services/rendering/http_mode.go

@@ -2,6 +2,7 @@ package rendering
 
 import (
 	"context"
+	"fmt"
 	"io"
 	"net"
 	"net/http"
@@ -20,14 +21,13 @@ var netTransport = &http.Transport{
 	TLSHandshakeTimeout: 5 * time.Second,
 }
 
+var netClient = &http.Client{
+	Transport: netTransport,
+}
+
 func (rs *RenderingService) renderViaHttp(ctx context.Context, opts Opts) (*RenderResult, error) {
 	filePath := rs.getFilePathForNewImage()
 
-	var netClient = &http.Client{
-		Timeout:   opts.Timeout,
-		Transport: netTransport,
-	}
-
 	rendererUrl, err := url.Parse(rs.Cfg.RendererUrl)
 	if err != nil {
 		return nil, err
@@ -35,10 +35,10 @@ func (rs *RenderingService) renderViaHttp(ctx context.Context, opts Opts) (*Rend
 
 	queryParams := rendererUrl.Query()
 	queryParams.Add("url", rs.getURL(opts.Path))
-	queryParams.Add("renderKey", rs.getRenderKey(opts.UserId, opts.OrgId, opts.OrgRole))
+	queryParams.Add("renderKey", rs.getRenderKey(opts.OrgId, opts.UserId, opts.OrgRole))
 	queryParams.Add("width", strconv.Itoa(opts.Width))
 	queryParams.Add("height", strconv.Itoa(opts.Height))
-	queryParams.Add("domain", rs.getLocalDomain())
+	queryParams.Add("domain", rs.domain)
 	queryParams.Add("timezone", isoTimeOffsetToPosixTz(opts.Timezone))
 	queryParams.Add("encoding", opts.Encoding)
 	queryParams.Add("timeout", strconv.Itoa(int(opts.Timeout.Seconds())))
@@ -49,20 +49,48 @@ func (rs *RenderingService) renderViaHttp(ctx context.Context, opts Opts) (*Rend
 		return nil, err
 	}
 
+	reqContext, cancel := context.WithTimeout(ctx, opts.Timeout+time.Second*2)
+	defer cancel()
+
+	req = req.WithContext(reqContext)
+
 	// make request to renderer server
 	resp, err := netClient.Do(req)
 	if err != nil {
-		return nil, err
+		rs.log.Error("Failed to send request to remote rendering service.", "error", err)
+		return nil, fmt.Errorf("Failed to send request to remote rendering service. %s", err)
 	}
 
 	// save response to file
 	defer resp.Body.Close()
+
+	// check for timeout first
+	if reqContext.Err() == context.DeadlineExceeded {
+		rs.log.Info("Rendering timed out")
+		return nil, ErrTimeout
+	}
+
+	// if we didnt get a 200 response, something went wrong.
+	if resp.StatusCode != http.StatusOK {
+		rs.log.Error("Remote rendering request failed", "error", resp.Status)
+		return nil, fmt.Errorf("Remote rendering request failed. %d: %s", resp.StatusCode, resp.Status)
+	}
+
 	out, err := os.Create(filePath)
 	if err != nil {
 		return nil, err
 	}
 	defer out.Close()
-	io.Copy(out, resp.Body)
+	_, err = io.Copy(out, resp.Body)
+	if err != nil {
+		// check that we didnt timeout while receiving the response.
+		if reqContext.Err() == context.DeadlineExceeded {
+			rs.log.Info("Rendering timed out")
+			return nil, ErrTimeout
+		}
+		rs.log.Error("Remote rendering request failed", "error", err)
+		return nil, fmt.Errorf("Remote rendering request failed.  %s", err)
+	}
 
 	return &RenderResult{FilePath: filePath}, err
 }