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resource: Fix multi-threaded image processing issue

When doing something like this with the same image from a partial used in, say, both the home page and the single page:

```bash
{{ with $img }}
{{ $big := .Fill "1024x512 top" }}
{{ $small := $big.Resize "512x" }}
{{ end }}
```

There would be timing issues making Hugo in some cases try to process the same image with the same instructions in parallel.

You would experience errors of type:

```bash
png: invalid format: not enough pixel data
```

This commit works around that by adding a mutex per image. This should also improve the performance, sligthly, as it avoids duplicate work.

The current workaround before this fix is to always operate on the original:

```bash
{{ with $img }}
{{ $big := .Fill "1024x512 top" }}
{{ $small := .Fill "512x256 top" }}
{{ end }}
```

Fixes #4404
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bep committed Feb 13, 2018
1 parent 2851af0 commit d8fdffb55268464d54558d6f9cd3874b612dc7c7
Showing with 120 additions and 5 deletions.
  1. +3 −0 resource/image.go
  2. +7 −1 resource/image_cache.go
  3. +68 −0 resource/image_test.go
  4. +42 −4 resource/testhelpers_test.go
@@ -112,6 +112,9 @@ type Image struct {
copyToDestinationInit sync.Once
// Lock used when creating alternate versions of this image.
createMu sync.Mutex
imaging *Imaging
hash string
@@ -28,7 +28,8 @@ type imageCache struct {
absCacheDir string
pathSpec *helpers.PathSpec
mu sync.RWMutex
store map[string]*Image
store map[string]*Image
}
func (c *imageCache) isInCache(key string) bool {
@@ -69,6 +70,11 @@ func (c *imageCache) getOrCreate(
}
// Now look in the file cache.
// Multiple Go routines can invoke same operation on the same image, so
// we need to make sure this is serialized per source image.
parent.createMu.Lock()
defer parent.createMu.Unlock()
cacheFilename := filepath.Join(c.absCacheDir, key)
// The definition of this counter is not that we have processed that amount
@@ -15,8 +15,12 @@ package resource
import (
"fmt"
"math/rand"
"strconv"
"testing"
"sync"
"github.com/stretchr/testify/require"
)
@@ -141,6 +145,51 @@ func TestImageTransformLongFilename(t *testing.T) {
assert.Equal("/a/_hu59e56ffff1bc1d8d122b1403d34e039f_90587_c876768085288f41211f768147ba2647.jpg", resized.RelPermalink())
}
func TestImageTransformConcurrent(t *testing.T) {
var wg sync.WaitGroup
assert := require.New(t)
spec := newTestResourceOsFs(assert)
image := fetchImageForSpec(spec, assert, "sunset.jpg")
for i := 0; i < 4; i++ {
wg.Add(1)
go func(id int) {
defer wg.Done()
for j := 0; j < 5; j++ {
img := image
for k := 0; k < 2; k++ {
r1, err := img.Resize(fmt.Sprintf("%dx", id-k))
if err != nil {
t.Fatal(err)
}
if r1.Width() != id-k {
t.Fatalf("Width: %d:%d", r1.Width(), j)
}
r2, err := r1.Resize(fmt.Sprintf("%dx", id-k-1))
if err != nil {
t.Fatal(err)
}
_, err = r2.decodeSource()
if err != nil {
t.Fatal("Err decode:", err)
}
img = r1
}
}
}(i + 20)
}
wg.Wait()
}
func TestDecodeImaging(t *testing.T) {
assert := require.New(t)
m := map[string]interface{}{
@@ -208,3 +257,22 @@ func TestImageWithMetadata(t *testing.T) {
assert.Equal("Sunset #1", resized.Name())
}
func BenchmarkResizeParallel(b *testing.B) {
assert := require.New(b)
img := fetchSunset(assert)
b.RunParallel(func(pb *testing.PB) {
for pb.Next() {
w := rand.Intn(10) + 10
resized, err := img.Resize(strconv.Itoa(w) + "x")
if err != nil {
b.Fatal(err)
}
_, err = resized.Resize(strconv.Itoa(w-1) + "x")
if err != nil {
b.Fatal(err)
}
}
})
}
@@ -6,8 +6,11 @@ import (
"image"
"io"
"io/ioutil"
"os"
"path"
"runtime"
"strings"
"github.com/gohugoio/hugo/helpers"
"github.com/gohugoio/hugo/hugofs"
@@ -45,17 +48,53 @@ func newTestResourceSpecForBaseURL(assert *require.Assertions, baseURL string) *
return spec
}
func newTestResourceOsFs(assert *require.Assertions) *Spec {
cfg := viper.New()
cfg.Set("baseURL", "https://example.com")
workDir, err := ioutil.TempDir("", "hugores")
if runtime.GOOS == "darwin" && !strings.HasPrefix(workDir, "/private") {
// To get the entry folder in line with the rest. This its a little bit
// mysterious, but so be it.
workDir = "/private" + workDir
}
contentDir := "base"
cfg.Set("workingDir", workDir)
cfg.Set("contentDir", contentDir)
cfg.Set("resourceDir", filepath.Join(workDir, "res"))
fs := hugofs.NewFrom(hugofs.Os, cfg)
fs.Destination = &afero.MemMapFs{}
s, err := helpers.NewPathSpec(fs, cfg)
assert.NoError(err)
spec, err := NewSpec(s, media.DefaultTypes)
assert.NoError(err)
return spec
}
func fetchSunset(assert *require.Assertions) *Image {
return fetchImage(assert, "sunset.jpg")
}
func fetchImage(assert *require.Assertions, name string) *Image {
spec := newTestResourceSpec(assert)
return fetchImageForSpec(spec, assert, name)
}
func fetchImageForSpec(spec *Spec, assert *require.Assertions, name string) *Image {
src, err := os.Open("testdata/" + name)
assert.NoError(err)
spec := newTestResourceSpec(assert)
workingDir := spec.Cfg.GetString("workingDir")
f := filepath.Join(workingDir, name)
out, err := spec.Fs.Source.Create("/b/" + name)
out, err := spec.Fs.Source.Create(f)
assert.NoError(err)
_, err = io.Copy(out, src)
out.Close()
@@ -66,11 +105,10 @@ func fetchImage(assert *require.Assertions, name string) *Image {
return path.Join("/a", s)
}
r, err := spec.NewResourceFromFilename(factory, "/public", "/b/"+name, name)
r, err := spec.NewResourceFromFilename(factory, "/public", f, name)
assert.NoError(err)
assert.IsType(&Image{}, r)
return r.(*Image)
}
func assertFileCache(assert *require.Assertions, fs *hugofs.Fs, filename string, width, height int) {

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