feat(opentelemetry-web): capture decodedBodySize / http.response_content_length_uncompressed (#2343)

Co-authored-by: Valentin Marchaud <contact@vmarchaud.fr>

Author: t2t2

packages/opentelemetry-web/src/enums/PerformanceTimingNames.ts

@@ -17,6 +17,7 @@
 export enum PerformanceTimingNames {
   CONNECT_END = 'connectEnd',
   CONNECT_START = 'connectStart',
+  DECODED_BODY_SIZE = 'decodedBodySize',
   DOM_COMPLETE = 'domComplete',
   DOM_CONTENT_LOADED_EVENT_END = 'domContentLoadedEventEnd',
   DOM_CONTENT_LOADED_EVENT_START = 'domContentLoadedEventStart',

packages/opentelemetry-web/src/types.ts

@@ -18,6 +18,7 @@ import { PerformanceTimingNames } from './enums/PerformanceTimingNames';
 export type PerformanceEntries = {
   [PerformanceTimingNames.CONNECT_END]?: number;
   [PerformanceTimingNames.CONNECT_START]?: number;
+  [PerformanceTimingNames.DECODED_BODY_SIZE]?: number;
   [PerformanceTimingNames.DOM_COMPLETE]?: number;
   [PerformanceTimingNames.DOM_CONTENT_LOADED_EVENT_END]?: number;
   [PerformanceTimingNames.DOM_CONTENT_LOADED_EVENT_START]?: number;

packages/opentelemetry-web/src/utils.ts

@@ -87,11 +87,19 @@ export function addSpanNetworkEvents(
   addSpanNetworkEvent(span, PTN.REQUEST_START, resource);
   addSpanNetworkEvent(span, PTN.RESPONSE_START, resource);
   addSpanNetworkEvent(span, PTN.RESPONSE_END, resource);
-  const contentLength = resource[PTN.ENCODED_BODY_SIZE];
-  if (contentLength !== undefined) {
+  const encodedLength = resource[PTN.ENCODED_BODY_SIZE];
+  if (encodedLength !== undefined) {
     span.setAttribute(
       SemanticAttributes.HTTP_RESPONSE_CONTENT_LENGTH,
-      contentLength
+      encodedLength
+    );
+  }
+  const decodedLength = resource[PTN.DECODED_BODY_SIZE];
+  // Spec: Not set if transport encoding not used (in which case encoded and decoded sizes match)
+  if (decodedLength !== undefined && encodedLength !== decodedLength) {
+    span.setAttribute(
+      SemanticAttributes.HTTP_RESPONSE_CONTENT_LENGTH_UNCOMPRESSED,
+      decodedLength
     );
   }
 }

packages/opentelemetry-web/test/utils.test.ts

@@ -146,14 +146,34 @@ describe('utils', () => {
         [PTN.REQUEST_START]: 123,
         [PTN.RESPONSE_START]: 123,
         [PTN.RESPONSE_END]: 123,
-        [PTN.ENCODED_BODY_SIZE]: 123,
+        [PTN.DECODED_BODY_SIZE]: 123,
+        [PTN.ENCODED_BODY_SIZE]: 61,
       } as PerformanceEntries;
 
       assert.strictEqual(addEventSpy.callCount, 0);
 
       addSpanNetworkEvents(span, entries);
 
       assert.strictEqual(addEventSpy.callCount, 9);
+      assert.strictEqual(setAttributeSpy.callCount, 2);
+    });
+    it('should only include encoded size when content encoding is being used', () => {
+      const addEventSpy = sinon.spy();
+      const setAttributeSpy = sinon.spy();
+      const span = ({
+        addEvent: addEventSpy,
+        setAttribute: setAttributeSpy,
+      } as unknown) as tracing.Span;
+      const entries = {
+        [PTN.DECODED_BODY_SIZE]: 123,
+        [PTN.ENCODED_BODY_SIZE]: 123,
+      } as PerformanceEntries;
+
+      assert.strictEqual(setAttributeSpy.callCount, 0);
+
+      addSpanNetworkEvents(span, entries);
+
+      assert.strictEqual(addEventSpy.callCount, 0);
       assert.strictEqual(setAttributeSpy.callCount, 1);
     });
   });