Add injector to resize images on the fly

via graphicsmagick

.gitlab-ci.yml

@@ -32,7 +32,7 @@ verify:
     GITALY_ADDRESS: "tcp://gitaly:8075"
   script:
   - go version
-  - apt-get update && apt-get -y install libimage-exiftool-perl
+  - apt-get update && apt-get -y install libimage-exiftool-perl graphicsmagick
   - make test
 
 test using go 1.13:

README.md

@@ -212,6 +212,28 @@ images. If you installed GitLab:
     sudo yum install perl-Image-ExifTool
     ```
 
+### GraphicsMagick (**experimental**)
+
+Workhorse has an experimental feature that allows us to rescale images on-the-fly.
+If you do not run Workhorse in a container where the `gm` tool is already installed,
+you will have to install it on your host machine instead:
+
+#### macOS
+
+```sh
+brew install graphicsmagick
+```
+
+#### Debian/Ubuntu
+
+```sh
+sudo apt-get install graphicsmagick
+```
+
+For installation on other platforms, please consult http://www.graphicsmagick.org/README.html.
+
+Note that Omnibus containers already come with `gm` installed.
+
 ## Error tracking
 
 GitLab-Workhorse supports remote error tracking with

internal/imageresizer/image_resizer.go

+package imageresizer
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"os"
+	"os/exec"
+	"strings"
+	"sync/atomic"
+	"syscall"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+
+	"gitlab.com/gitlab-org/labkit/correlation"
+	"gitlab.com/gitlab-org/labkit/log"
+
+	"gitlab.com/gitlab-org/labkit/tracing"
+
+	"github.com/sirupsen/logrus"
+
+	"gitlab.com/gitlab-org/gitlab-workhorse/internal/helper"
+	"gitlab.com/gitlab-org/gitlab-workhorse/internal/senddata"
+)
+
+type resizer struct{ senddata.Prefix }
+
+var SendScaledImage = &resizer{"send-scaled-img:"}
+
+type resizeParams struct {
+	Location string
+	Width    uint
+}
+
+const maxImageScalerProcs = 100
+
+var numScalerProcs int32 = 0
+
+// Images might be located remotely in object storage, in which case we need to stream
+// it via http(s)
+var httpTransport = tracing.NewRoundTripper(correlation.NewInstrumentedRoundTripper(&http.Transport{
+	Proxy: http.ProxyFromEnvironment,
+	DialContext: (&net.Dialer{
+		Timeout:   30 * time.Second,
+		KeepAlive: 10 * time.Second,
+	}).DialContext,
+	MaxIdleConns:          2,
+	IdleConnTimeout:       30 * time.Second,
+	TLSHandshakeTimeout:   10 * time.Second,
+	ExpectContinueTimeout: 10 * time.Second,
+	ResponseHeaderTimeout: 30 * time.Second,
+}))
+
+var httpClient = &http.Client{
+	Transport: httpTransport,
+}
+
+var imageResizeConcurrencyMax = prometheus.NewCounter(
+	prometheus.CounterOpts{
+		Name: "gitlab_workhorse_max_image_resize_requests_exceeded_total",
+		Help: "Amount of image resizing requests that exceed the maximum allowed scaler processes",
+	},
+)
+
+func init() {
+	prometheus.MustRegister(imageResizeConcurrencyMax)
+}
+
+// This Injecter forks into graphicsmagick to resize an image identified by path or URL
+// and streams the resized image back to the client
+func (r *resizer) Inject(w http.ResponseWriter, req *http.Request, paramsData string) {
+	logger := log.ContextLogger(req.Context())
+	params, err := r.unpackParameters(paramsData)
+	if err != nil {
+		// This means the response header coming from Rails was malformed; there is no way
+		// to sensibly recover from this other than failing fast
+		helper.Fail500(w, req, fmt.Errorf("ImageResizer: Failed reading image resize params: %v", err))
+		return
+	}
+
+	sourceImageReader, err := openSourceImage(params.Location)
+	if err != nil {
+		// This means we cannot even read the input image; fail fast.
+		helper.Fail500(w, req, fmt.Errorf("ImageResizer: Failed opening image data stream: %v", err))
+		return
+	}
+	defer sourceImageReader.Close()
+
+	// Past this point we attempt to rescale the image; if this should fail for any reason, we
+	// simply fail over to rendering out the original image unchanged.
+	imageReader, resizeCmd := tryResizeImage(req.Context(), sourceImageReader, params.Width, logger)
+	defer helper.CleanUpProcessGroup(resizeCmd)
+
+	w.Header().Del("Content-Length")
+	bytesWritten, err := io.Copy(w, imageReader)
+	if err != nil {
+		helper.Fail500(w, req, err)
+		return
+	}
+
+	logger.WithField("bytes_written", bytesWritten).Print("ImageResizer: success")
+}
+
+func (r *resizer) unpackParameters(paramsData string) (*resizeParams, error) {
+	var params resizeParams
+	if err := r.Unpack(&params, paramsData); err != nil {
+		return nil, err
+	}
+
+	if params.Location == "" {
+		return nil, fmt.Errorf("ImageResizer: Location is empty")
+	}
+
+	return &params, nil
+}
+
+// Attempts to rescale the given image data, or in case of errors, falls back to the original image.
+func tryResizeImage(ctx context.Context, r io.Reader, width uint, logger *logrus.Entry) (io.Reader, *exec.Cmd) {
+	// Only allow more scaling requests if we haven't yet reached the maximum allows number
+	// of concurrent graphicsmagick processes
+	if n := atomic.AddInt32(&numScalerProcs, 1); n > maxImageScalerProcs {
+		atomic.AddInt32(&numScalerProcs, -1)
+		imageResizeConcurrencyMax.Inc()
+		return r, nil
+	}
+
+	go func() {
+		<-ctx.Done()
+		atomic.AddInt32(&numScalerProcs, -1)
+	}()
+
+	resizeCmd, resizedImageReader, err := startResizeImageCommand(ctx, r, logger.Writer(), width)
+	if err != nil {
+		logger.WithError(err).Error("ImageResizer: failed forking into graphicsmagick")
+		return r, nil
+	}
+	return resizedImageReader, resizeCmd
+}
+
+func startResizeImageCommand(ctx context.Context, imageReader io.Reader, errorWriter io.Writer, width uint) (*exec.Cmd, io.ReadCloser, error) {
+	cmd := exec.CommandContext(ctx, "gm", "convert", "-resize", fmt.Sprintf("%dx", width), "-", "-")
+	cmd.Stdin = imageReader
+	cmd.Stderr = errorWriter
+	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
+
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		return nil, nil, err
+	}
+
+	if err := cmd.Start(); err != nil {
+		return nil, nil, err
+	}
+
+	return cmd, stdout, nil
+}
+
+func isURL(location string) bool {
+	return strings.HasPrefix(location, "http://") || strings.HasPrefix(location, "https://")
+}
+
+func openSourceImage(location string) (io.ReadCloser, error) {
+	if !isURL(location) {
+		return os.Open(location)
+	}
+
+	res, err := httpClient.Get(location)
+	if err != nil {
+		return nil, err
+	}
+
+	if res.StatusCode != http.StatusOK {
+		res.Body.Close()
+
+		return nil, fmt.Errorf("ImageResizer: cannot read data from %q: %d %s",
+			location, res.StatusCode, res.Status)
+	}
+
+	return res.Body, nil
+}

internal/upstream/routes.go

@@ -17,6 +17,7 @@ import (
 	"gitlab.com/gitlab-org/gitlab-workhorse/internal/config"
 	"gitlab.com/gitlab-org/gitlab-workhorse/internal/git"
 	"gitlab.com/gitlab-org/gitlab-workhorse/internal/helper"
+	"gitlab.com/gitlab-org/gitlab-workhorse/internal/imageresizer"
 	"gitlab.com/gitlab-org/gitlab-workhorse/internal/lfs"
 	proxypkg "gitlab.com/gitlab-org/gitlab-workhorse/internal/proxy"
 	"gitlab.com/gitlab-org/gitlab-workhorse/internal/queueing"
@@ -153,6 +154,7 @@ func buildProxy(backend *url.URL, version string, rt http.RoundTripper) http.Han
 		git.SendSnapshot,
 		artifacts.SendEntry,
 		sendurl.SendURL,
+		imageresizer.SendScaledImage,
 	)
 }
 

main_test.go

@@ -6,6 +6,7 @@ import (
 	"encoding/base64"
 	"encoding/json"
 	"fmt"
+	"image/png"
 	"io"
 	"io/ioutil"
 	"net/http"
@@ -368,6 +369,23 @@ func TestArtifactsGetSingleFile(t *testing.T) {
 	assertNginxResponseBuffering(t, "no", resp, "GET %q: nginx response buffering", resourcePath)
 }
 
+func TestImageResizing(t *testing.T) {
+	imageLocation := `testdata/image.png`
+	requestedWidth := 40
+	jsonParams := fmt.Sprintf(`{"Location":"%s","Width":%d}`, imageLocation, requestedWidth)
+	resourcePath := "/uploads/-/system/user/avatar/123/avatar.png?width=40"
+
+	resp, body, err := doSendDataRequest(resourcePath, "send-scaled-img", jsonParams)
+	require.NoError(t, err, "send resize request")
+	assert.Equal(t, 200, resp.StatusCode, "GET %q: status code", resourcePath)
+
+	img, err := png.Decode(bytes.NewReader(body))
+	require.NoError(t, err, "decode resized image")
+
+	bounds := img.Bounds()
+	require.Equal(t, requestedWidth, bounds.Max.X-bounds.Min.X, "width after resizing")
+}
+
 func TestSendURLForArtifacts(t *testing.T) {
 	expectedBody := strings.Repeat("CONTENT!", 1024)