feat: add etag for raw api (#2018)

app/api/controller/repo/raw.go

@@ -22,6 +22,7 @@ import (
 	"github.com/harness/gitness/app/api/usererror"
 	"github.com/harness/gitness/app/auth"
 	"github.com/harness/gitness/git"
+	"github.com/harness/gitness/git/sha"
 	"github.com/harness/gitness/types/enum"
 )
 
@@ -32,10 +33,10 @@ func (c *Controller) Raw(ctx context.Context,
 	repoRef string,
 	gitRef string,
 	path string,
-) (io.ReadCloser, int64, error) {
+) (io.ReadCloser, int64, sha.SHA, error) {
 	repo, err := c.getRepoCheckAccess(ctx, session, repoRef, enum.PermissionRepoView, true)
 	if err != nil {
-		return nil, 0, err
+		return nil, 0, sha.Nil, err
 	}
 
 	// set gitRef to default branch in case an empty reference was provided
@@ -52,12 +53,12 @@ func (c *Controller) Raw(ctx context.Context,
 		IncludeLatestCommit: false,
 	})
 	if err != nil {
-		return nil, 0, fmt.Errorf("failed to read tree node: %w", err)
+		return nil, 0, sha.Nil, fmt.Errorf("failed to read tree node: %w", err)
 	}
 
 	// viewing Raw content is only supported for blob content
 	if treeNodeOutput.Node.Type != git.TreeNodeTypeBlob {
-		return nil, 0, usererror.BadRequestf(
+		return nil, 0, sha.Nil, usererror.BadRequestf(
 			"Object in '%s' at '/%s' is of type '%s'. Only objects of type %s support raw viewing.",
 			gitRef, path, treeNodeOutput.Node.Type, git.TreeNodeTypeBlob)
 	}
@@ -68,8 +69,8 @@ func (c *Controller) Raw(ctx context.Context,
 		SizeLimit:  0, // no size limit, we stream whatever data there is
 	})
 	if err != nil {
-		return nil, 0, fmt.Errorf("failed to read blob: %w", err)
+		return nil, 0, sha.Nil, fmt.Errorf("failed to read blob: %w", err)
 	}
 
-	return blobReader.Content, blobReader.ContentSize, nil
+	return blobReader.Content, blobReader.ContentSize, blobReader.SHA, nil
 }

app/api/handler/repo/raw.go

@@ -41,7 +41,7 @@ func HandleRaw(repoCtrl *repo.Controller) http.HandlerFunc {
 		gitRef := request.GetGitRefFromQueryOrDefault(r, "")
 		path := request.GetOptionalRemainderFromPath(r)
 
-		dataReader, dataLength, err := repoCtrl.Raw(ctx, session, repoRef, gitRef, path)
+		dataReader, dataLength, sha, err := repoCtrl.Raw(ctx, session, repoRef, gitRef, path)
 		if err != nil {
 			render.TranslatedUserError(ctx, w, err)
 			return
@@ -53,8 +53,14 @@ func HandleRaw(repoCtrl *repo.Controller) http.HandlerFunc {
 			}
 		}()
 
-		w.Header().Add("Content-Length", fmt.Sprint(dataLength))
+		ifNoneMatch, ok := request.GetIfNoneMatchFromHeader(r)
+		if ok && ifNoneMatch == sha.String() {
+			w.WriteHeader(http.StatusNotModified)
+			return
+		}
 
+		w.Header().Add("Content-Length", fmt.Sprint(dataLength))
+		w.Header().Add(request.HeaderETag, sha.String())
 		render.Reader(ctx, w, http.StatusOK, dataReader)
 	}
 }

app/api/middleware/nocache/nocache.go

@@ -0,0 +1,48 @@
+// Copyright 2023 Harness, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package nocache
+
+import (
+	"net/http"
+	"time"
+)
+
+// Ported from Chi's middleware, source:
+// https://github.com/go-chi/chi/blob/v5.0.12/middleware/nocache.go
+
+// Modified the middleware to retain ETags.
+
+var epoch = time.Unix(0, 0).Format(time.RFC1123)
+
+var noCacheHeaders = map[string]string{
+	"Expires":         epoch,
+	"Cache-Control":   "no-cache, no-store, no-transform, must-revalidate, private, max-age=0",
+	"Pragma":          "no-cache",
+	"X-Accel-Expires": "0",
+}
+
+// NoCache is same as chi's default NoCache middleware except it doesn't remove etag headers.
+func NoCache(h http.Handler) http.Handler {
+	fn := func(w http.ResponseWriter, r *http.Request) {
+		// Set our NoCache headers
+		for k, v := range noCacheHeaders {
+			w.Header().Set(k, v)
+		}
+
+		h.ServeHTTP(w, r)
+	}
+
+	return http.HandlerFunc(fn)
+}

app/api/request/common.go

@@ -55,6 +55,9 @@ const (
 	HeaderUserAgent       = "User-Agent"
 	HeaderAuthorization   = "Authorization"
 	HeaderContentEncoding = "Content-Encoding"
+
+	HeaderIfNoneMatch = "If-None-Match"
+	HeaderETag        = "ETag"
 )
 
 // GetOptionalRemainderFromPath returns the remainder ("*") from the path or an empty string if it doesn't exist.
@@ -166,3 +169,7 @@ func GetDeletedBeforeOrAtFromQuery(r *http.Request) (int64, bool, error) {
 func GetDeletedAtFromQuery(r *http.Request) (int64, bool, error) {
 	return QueryParamAsPositiveInt64(r, QueryParamDeletedAt)
 }
+
+func GetIfNoneMatchFromHeader(r *http.Request) (string, bool) {
+	return GetHeader(r, HeaderIfNoneMatch)
+}

app/router/api.go

@@ -68,6 +68,7 @@ import (
 	middlewareauthn "github.com/harness/gitness/app/api/middleware/authn"
 	"github.com/harness/gitness/app/api/middleware/encode"
 	"github.com/harness/gitness/app/api/middleware/logging"
+	"github.com/harness/gitness/app/api/middleware/nocache"
 	middlewareprincipal "github.com/harness/gitness/app/api/middleware/principal"
 	"github.com/harness/gitness/app/api/request"
 	"github.com/harness/gitness/app/auth/authn"
@@ -126,7 +127,7 @@ func NewAPIHandler(
 	r := chi.NewRouter()
 
 	// Apply common api middleware.
-	r.Use(middleware.NoCache)
+	r.Use(nocache.NoCache)
 	r.Use(middleware.Recoverer)
 
 	// configure logging middleware.