Fixes open-policy-agent#5310

docs/content/rest-api.md

@@ -732,6 +732,10 @@ The path separator is used to access values inside object and array documents. I
 - **instrument** - Instrument query evaluation and return a superset of performance metrics in addition to result. See [Performance Metrics](#performance-metrics) for more detail.
 - **strict-builtin-errors** - Treat built-in function call errors as fatal and return an error immediately.
 
+#### Request Headers
+
+- **Accept-Encoding: gzip**: Indicates the server should respond with a gzip encoded body
+
 #### Status Codes
 
 - **200** - no error

server/handlers/compress.go

@@ -34,9 +34,9 @@ func (w *compressResponseWriter) Write(b []byte) (int, error) {
 
 func CompressHandler(handler http.Handler) http.Handler {
 	return http.HandlerFunc(func(responseWriter http.ResponseWriter, request *http.Request) {
-		// this handler applies only for data and compile endpoints
-		shouldApplyCompression := isDataEndpoint(request) || isCompileEndpoint(request)
-		if !shouldApplyCompression {
+		// this handler applies only for data and compile endpoints for selected HTTP methods
+		enabledForEndpoint := isDataEndpoint(request) || isCompileEndpoint(request)
+		if !enabledForEndpoint {
 			handler.ServeHTTP(responseWriter, request)
 			return
 		}
@@ -54,10 +54,10 @@ func CompressHandler(handler http.Handler) http.Handler {
 		gzipWriter.Reset(&b)
 		defer func() {
 			gzipWriter.Close()
-			responseWriter.Header().Set("Content-Length", fmt.Sprint(len(b.Bytes())))
+			responseWriter.Header().Set(contentLengthHeader, fmt.Sprint(len(b.Bytes())))
 			_, err := responseWriter.Write(b.Bytes())
 			if err != nil {
-				log.Fatalf("Error writing the compressed response: %v", err)
+				log.Fatalf("Error writing the compressed response: %s\n", err)
 			}
 		}()
 
@@ -67,11 +67,21 @@ func CompressHandler(handler http.Handler) http.Handler {
 }
 
 func isDataEndpoint(req *http.Request) bool {
-	return strings.HasPrefix(req.URL.Path, "/v1/data") || strings.HasPrefix(req.URL.Path, "/v0/data")
+	isPostOrGetMethod := isPostMethod(req) || isGetMethod(req)
+	isV1rV0 := strings.HasPrefix(req.URL.Path, "/v1/data") || strings.HasPrefix(req.URL.Path, "/v0/data")
+	return isPostOrGetMethod && isV1rV0
 }
 
 func isCompileEndpoint(req *http.Request) bool {
-	return strings.HasPrefix(req.URL.Path, "/v1/compile")
+	return isPostMethod(req) && strings.HasPrefix(req.URL.Path, "/v1/compile")
+}
+
+func isPostMethod(req *http.Request) bool {
+	return req.Method == "POST"
+}
+
+func isGetMethod(req *http.Request) bool {
+	return req.Method == "GET"
 }
 
 var gzipPool = sync.Pool{

server/handlers/compress_test.go

@@ -16,7 +16,7 @@ const (
 	requestBody  = "Hello World!\n"
 )
 
-func executeRequest(w *httptest.ResponseRecorder, path string, acceptEncoding string) {
+func executeRequest(w *httptest.ResponseRecorder, path string, method string, acceptEncoding string) {
 	CompressHandler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "application/json")
 		_, err := io.WriteString(w, requestBody)
@@ -25,7 +25,7 @@ func executeRequest(w *httptest.ResponseRecorder, path string, acceptEncoding st
 		}
 	})).ServeHTTP(w, &http.Request{
 		URL:    &url.URL{Path: path},
-		Method: "GET",
+		Method: method,
 		Header: http.Header{
 			"Accept-Encoding": []string{acceptEncoding},
 		},
@@ -36,7 +36,7 @@ func TestCompressHandlerWithGzipOnInScopeEndpoints(t *testing.T) {
 	endpoints := []string{"/v0/data", "/v1/data", "/v1/compile"}
 	for _, endpoint := range endpoints {
 		w := httptest.NewRecorder()
-		executeRequest(w, endpoint, gzipEncoding)
+		executeRequest(w, endpoint, "POST", gzipEncoding)
 		contentEncodingValue := w.Result().Header.Get("Content-Encoding")
 		if contentEncodingValue != gzipEncoding {
 			t.Errorf("wrong content encoding, got %q want %q", contentEncodingValue, gzipEncoding)
@@ -55,7 +55,7 @@ func TestCompressHandlerWithGzipOnInScopeEndpoints(t *testing.T) {
 
 func TestHandlerOnEndpointsWithoutCompression(t *testing.T) {
 	w := httptest.NewRecorder()
-	executeRequest(w, "/metrics", gzipEncoding)
+	executeRequest(w, "/metrics", "GET", gzipEncoding)
 	contentEncodingValue := w.Result().Header.Get("Content-Encoding")
 	if contentEncodingValue != "" {
 		t.Errorf("wrong content encoding, got %q want %q", contentEncodingValue, gzipEncoding)