Remove documentStart

GoogleChrome · Nov 18, 2024 · 7e85484 · 7e85484
1 parent a9e2d23
commit 7e85484
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Showing 6 changed files with 14 additions and 33 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -5,7 +5,7 @@
 - **[BREAKING]** Remove the deprecated `onFID()` function ([#519](https://github.com/GoogleChrome/web-vitals/pull/519))
 - **[BREAKING]** Change browser support policy to Baseline Widely Available ([#525](https://github.com/GoogleChrome/web-vitals/pull/525))
 - **[BREAKING]** Sort the classes that appear in attribution selectors to reduce cardinality ([#518](https://github.com/GoogleChrome/web-vitals/pull/518))
-- **[BREAKING]** Add interoperable TTFB and `documentDuration` to measure Early Hints better ([#566](https://github.com/GoogleChrome/web-vitals/pull/566))
+- **[BREAKING]** Add interoperable TTFB to measure Early Hints consistently ([#566](https://github.com/GoogleChrome/web-vitals/pull/566))
 - Cap INP breakdowns to INP duration ([#528](https://github.com/GoogleChrome/web-vitals/pull/528))
 - Cap LCP load duration to LCP time ([#527](https://github.com/GoogleChrome/web-vitals/pull/527))
 

diff --git a/README.md b/README.md
@@ -1009,16 +1009,6 @@ export interface TTFBAttribution {
    * processing time.
    */
   requestDuration: number;
-  /**
-   * The total time, after TTFB, after which the document started to be
-   * received (i.e. when the document HTTP headers start to artive).
-   * This will only be non-zero for servers using Early Hints and where
-   * browsers support sending this additional timing. It is the time between
-   * the Early Hints first response (TTFB) and when the actual document
-   * response started and is useful to understand how much later the document
-   * TTFB is from the actual TTFB.
-   */
-  documentDuration: number;
   /**
    * The `navigation` entry of the current page, which is useful for diagnosing
    * general page load issues. This can be used to access `serverTiming` for

diff --git a/src/attribution/onLCP.ts b/src/attribution/onLCP.ts
@@ -45,7 +45,15 @@ const attributeLCP = (metric: LCPMetric): LCPMetricWithAttribution => {
           .getEntriesByType('resource')
           .filter((e) => e.name === lcpEntry.url)[0];
 
-      const ttfb = Math.max(0, navigationEntry.responseStart - activationStart);
+      const ttfb = Math.max(
+        0,
+        // From Chrome 115 until, Chrome reported responseStart as the document
+        // bytes, rather than Early Hint bytes. Prefer the Early Hint bytes
+        // (firstInterimResponseStart) for consistency with other browers, if
+        // non-zero
+        navigationEntry.firstInterimResponseStart ??
+          navigationEntry.responseStart - activationStart,
+      );
 
       const lcpRequestStart = Math.max(
         ttfb,

diff --git a/src/attribution/onTTFB.ts b/src/attribution/onTTFB.ts
@@ -30,7 +30,6 @@ const attributeTTFB = (metric: TTFBMetric): TTFBMetricWithAttribution => {
     dnsDuration: 0,
     connectionDuration: 0,
     requestDuration: 0,
-    documentDuration: 0,
   };
 
   if (metric.entries.length) {
@@ -58,11 +57,6 @@ const attributeTTFB = (metric: TTFBMetric): TTFBMetricWithAttribution => {
       0,
     );
 
-    // Fallback to responseStart for finalResponseHeadersStart
-    const finalResponseHeadersStart =
-      (navigationEntry.finalResponseHeadersStart ??
-        navigationEntry.responseStart) - activationStart;
-
     attribution = {
       waitingDuration: waitEnd,
       cacheDuration: dnsStart - waitEnd,
@@ -75,7 +69,6 @@ const attributeTTFB = (metric: TTFBMetric): TTFBMetricWithAttribution => {
       // service worker controlled requests were connectStart and connectEnd
       // are the same.
       requestDuration: metric.value - connectEnd,
-      documentDuration: finalResponseHeadersStart - metric.value,
       navigationEntry: navigationEntry,
     };
   }

diff --git a/src/onTTFB.ts b/src/onTTFB.ts
@@ -71,10 +71,10 @@ export const onTTFB = (
     const navigationEntry = getNavigationEntry();
 
     if (navigationEntry) {
-      // Form Chrome 115 until Chrome 132 (with flags), Chrome reported
-      // responseStart as the document bytes, rather than Early Hint bytes.
-      // Prefer the Early Hint bytes (firstInterimResponseStart) for
-      // consistency with other browers, if non-zero
+      // From Chrome 115 until, Chrome reported responseStart as the document
+      // bytes, rather than Early Hint bytes. Prefer the Early Hint bytes
+      // (firstInterimResponseStart) for consistency with other browers, if
+      // non-zero
       const responseStart =
         navigationEntry.firstInterimResponseStart ||
         navigationEntry.responseStart;

diff --git a/src/types/ttfb.ts b/src/types/ttfb.ts
@@ -62,16 +62,6 @@ export interface TTFBAttribution {
    * processing time.
    */
   requestDuration: number;
-  /**
-   * The total time, after TTFB, after which the document started to be
-   * received (i.e. when the document HTTP headers start to artive).
-   * This will only be non-zero for servers using Early Hints and where
-   * browsers support sending this additional timing. It is the time between
-   * the Early Hints first response (TTFB) and when the actual document
-   * response started and is useful to understand how much later the document
-   * TTFB is from the actual TTFB.
-   */
-  documentDuration: number;
   /**
    * The `navigation` entry of the current page, which is useful for diagnosing
    * general page load issues. This can be used to access `serverTiming` for