Adds etags for web static cached results (#136)

* adding tests

* updates

* removing superfluous error checking

* refactor

* tweaks

* double clutch

COVERAGE

@@ -1 +1 @@
-67.84
+67.90

web/cached_static_file.go

@@ -4,18 +4,24 @@ import (
 	"bytes"
 	"net/http"
 	"time"
+
+	"github.com/blend/go-sdk/webutil"
 )
 
 // CachedStaticFile is a memory mapped static file.
 type CachedStaticFile struct {
 	Path     string
 	Size     int
+	ETag     string
 	ModTime  time.Time
 	Contents *bytes.Reader
 }
 
 // Render implements Result.
 func (csf CachedStaticFile) Render(ctx *Ctx) error {
+	if csf.ETag != "" {
+		ctx.Response.Header().Set(webutil.HeaderETag, csf.ETag)
+	}
 	http.ServeContent(ctx.Response, ctx.Request, csf.Path, csf.ModTime, csf.Contents)
 	return nil
 }

web/static_file_server.go

@@ -7,6 +7,8 @@ import (
 	"os"
 	"regexp"
 	"sync"
+
+	"github.com/blend/go-sdk/webutil"
 )
 
 // NewStaticFileServer returns a new static file cache.
@@ -43,8 +45,9 @@ func OptStaticFileServerCacheDisabled(cacheDisabled bool) StaticFileserverOption
 }
 
 // StaticFileServer is a cache of static files.
-// It can operate in cached mode, or with `CacheDisabled` it will read from
-// disk for each request.
+// It can operate in cached mode, or with `CacheDisabled` set to `true`
+// it will read from disk for each request.
+// In cached mode, it automatically adds etags for files it caches.
 type StaticFileServer struct {
 	sync.RWMutex
 
@@ -110,28 +113,13 @@ func (sc *StaticFileServer) Action(r *Ctx) Result {
 func (sc *StaticFileServer) ServeFile(r *Ctx, filePath string) Result {
 	f, err := sc.ResolveFile(filePath)
 	if err != nil {
-		if os.IsNotExist(err) {
-			if r.DefaultProvider != nil {
-				return r.DefaultProvider.NotFound()
-			}
-			http.NotFound(r.Response, r.Request)
-			return nil
-		}
-		if r.DefaultProvider != nil {
-			return r.DefaultProvider.InternalError(err)
-		}
-		http.Error(r.Response, err.Error(), http.StatusInternalServerError)
-		return nil
+		return sc.fileError(r, err)
 	}
 	defer f.Close()
 
 	finfo, err := f.Stat()
 	if err != nil {
-		if r.DefaultProvider != nil {
-			return r.DefaultProvider.InternalError(err)
-		}
-		http.Error(r.Response, err.Error(), http.StatusInternalServerError)
-		return nil
+		return sc.fileError(r, err)
 	}
 	http.ServeContent(r.Response, r.Request, filePath, finfo.ModTime(), f)
 	return nil
@@ -142,18 +130,10 @@ func (sc *StaticFileServer) ServeFile(r *Ctx, filePath string) Result {
 func (sc *StaticFileServer) ServeCachedFile(r *Ctx, filepath string) Result {
 	file, err := sc.ResolveCachedFile(filepath)
 	if err != nil {
-		if os.IsNotExist(err) {
-			if r.DefaultProvider != nil {
-				return r.DefaultProvider.NotFound()
-			}
-			http.NotFound(r.Response, r.Request)
-			return nil
-		}
-		if r.DefaultProvider != nil {
-			return r.DefaultProvider.InternalError(err)
-		}
-		http.Error(r.Response, err.Error(), http.StatusInternalServerError)
-		return nil
+		return sc.fileError(r, err)
+	}
+	if file.ETag != "" {
+		r.Response.Header().Set(webutil.HeaderETag, file.ETag)
 	}
 	http.ServeContent(r.Response, r.Request, filepath, file.ModTime, file.Contents)
 	return nil
@@ -232,9 +212,25 @@ func (sc *StaticFileServer) ResolveCachedFile(filepath string) (*CachedStaticFil
 		Path:     filepath,
 		Contents: bytes.NewReader(contents),
 		ModTime:  finfo.ModTime(),
+		ETag:     webutil.ETag(contents),
 		Size:     len(contents),
 	}
 
 	sc.Cache[filepath] = file
 	return file, nil
 }
+
+func (sc *StaticFileServer) fileError(r *Ctx, err error) Result {
+	if os.IsNotExist(err) {
+		if r.DefaultProvider != nil {
+			return r.DefaultProvider.NotFound()
+		}
+		http.NotFound(r.Response, r.Request)
+		return nil
+	}
+	if r.DefaultProvider != nil {
+		return r.DefaultProvider.InternalError(err)
+	}
+	http.Error(r.Response, err.Error(), http.StatusInternalServerError)
+	return nil
+}

web/static_file_server_test.go

@@ -136,8 +136,8 @@ func TestStaticFileserverLiveNotFound(t *testing.T) {
 
 	cfs := NewStaticFileServer(
 		OptStaticFileServerSearchPaths(http.Dir("testdata")),
+		OptStaticFileServerCacheDisabled(true),
 	)
-	cfs.CacheDisabled = true
 	buffer := new(bytes.Buffer)
 	res := webutil.NewMockResponse(buffer)
 	req := webutil.NewMockRequest("GET", "/"+uuid.V4().String())
@@ -149,3 +149,23 @@ func TestStaticFileserverLiveNotFound(t *testing.T) {
 	assert.Equal(http.StatusNotFound, res.StatusCode())
 	assert.NotEmpty(buffer.Bytes())
 }
+
+func TestStaticFileserverAddsETag(t *testing.T) {
+	assert := assert.New(t)
+
+	cfs := NewStaticFileServer(
+		OptStaticFileServerSearchPaths(http.Dir("testdata")),
+		OptStaticFileServerCacheDisabled(false),
+	)
+	buffer := new(bytes.Buffer)
+	res := webutil.NewMockResponse(buffer)
+	req := webutil.NewMockRequest("GET", "/test_file.html")
+	result := cfs.Action(NewCtx(res, req, OptCtxRouteParams(RouteParameters{
+		RouteTokenFilepath: req.URL.Path,
+	})))
+
+	assert.Nil(result)
+	assert.Equal(http.StatusOK, res.StatusCode())
+	assert.NotEmpty(buffer.Bytes())
+	assert.NotEmpty(res.Header().Get(webutil.HeaderETag))
+}

webutil/constants.go

@@ -27,6 +27,7 @@ var (
 	HeaderSetCookie               = http.CanonicalHeaderKey("Set-Cookie")
 	HeaderCookie                  = http.CanonicalHeaderKey("Cookie")
 	HeaderDate                    = http.CanonicalHeaderKey("Date")
+	HeaderETag                    = http.CanonicalHeaderKey("etag")
 	HeaderCacheControl            = http.CanonicalHeaderKey("Cache-Control")
 	HeaderConnection              = http.CanonicalHeaderKey("Connection")
 	HeaderContentEncoding         = http.CanonicalHeaderKey("Content-Encoding")

webutil/etag.go

@@ -0,0 +1,13 @@
+package webutil
+
+import (
+	"crypto/md5"
+	"encoding/hex"
+)
+
+// ETag creates an etag for a given blob.
+func ETag(contents []byte) string {
+	hash := md5.New()
+	_, _ = hash.Write(contents)
+	return hex.EncodeToString(hash.Sum(nil))
+}

webutil/etag_test.go

@@ -0,0 +1,18 @@
+package webutil
+
+import (
+	"testing"
+
+	"github.com/blend/go-sdk/assert"
+)
+
+func TestETag(t *testing.T) {
+	assert := assert.New(t)
+
+	etag := ETag([]byte("a quick brown fox jumps over the something cool"))
+	assert.Equal("4743a94a6030d34968f838c94cf4a6fd", etag)
+
+	etag = ETag([]byte("something else that is really cool"))
+	assert.Equal("a8c90c3202be46c1d766b2c63d38332b", etag)
+
+}