Bug 1883391 - add telemetry to collect delta between OnDataFinished and OnStopRequest in CSSLoader. r=necko-reviewers,valentin

Differential Revision: https://phabricator.services.mozilla.com/D203945

layout/style/StreamLoader.cpp

@@ -7,6 +7,7 @@
 #include "mozilla/css/StreamLoader.h"
 #include "mozilla/StaticPrefs_network.h"
 #include "mozilla/Encoding.h"
+#include "mozilla/glean/GleanMetrics.h"
 #include "mozilla/TaskQueue.h"
 #include "nsContentUtils.h"
 #include "nsIChannel.h"
@@ -116,6 +117,13 @@ StreamLoader::OnStopRequest(nsIRequest* aRequest, nsresult aStatus) {
   // Resolution of parse promise fires onLoadEvent and this should not happen
   // before main thread OnStopRequest is dispatched.
   if (NS_IsMainThread()) {
+    if (mOnDataFinishedTime) {
+      // collect telemetry for the delta between OnDataFinished and
+      // OnStopRequest
+      TimeDuration delta = (TimeStamp::Now() - mOnDataFinishedTime);
+      glean::networking::http_content_cssloader_ondatafinished_to_onstop_delay
+          .AccumulateRawDuration(delta);
+    }
     mSheetLoadData->mSheet->BlockOrUnblockParsePromise(false);
   }
 
@@ -230,6 +238,9 @@ void StreamLoader::HandleBOM() {
 NS_IMETHODIMP
 StreamLoader::OnDataFinished(nsresult aResult) {
   if (StaticPrefs::network_send_OnDataFinished_cssLoader()) {
+    MOZ_ASSERT(mOnDataFinishedTime.IsNull(),
+               "OnDataFinished should only be called once");
+    mOnDataFinishedTime = TimeStamp::Now();
     return OnStopRequest(mRequest, aResult);
   }
 

layout/style/StreamLoader.h

@@ -60,6 +60,8 @@ class StreamLoader : public nsIThreadRetargetableStreamListener {
   bool mOnStopProcessingDone{false};
   RefPtr<SheetLoadDataHolder> mMainThreadSheetLoadData;
 
+  mozilla::TimeStamp mOnDataFinishedTime;
+
 #ifdef NIGHTLY_BUILD
   bool mChannelOpenFailed = false;
 #endif

netwerk/metrics.yaml

@@ -500,6 +500,21 @@ networking:
       - rjesup@mozilla.com
     expires: 130
 
+  http_content_cssloader_ondatafinished_to_onstop_delay:
+    type: timing_distribution
+    time_unit: millisecond
+    description: >
+      The time between processing OnDataFinished and processing OnStopRequest for CSSLoader in the content process
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1883391
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1883391
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - necko@mozilla.com
+    expires: 130
+
   http_1_download_throughput:
     type: custom_distribution
     unit: mbps