Bug 1328398 - Add telemetry to measure service worker launch time. r=bkelly,francois datareview=francois

This patch is mainly to add a probe to measure sw launch time. To do this, this
patch records the sw launch time when the sw is just spwaned and it's ready to
handle the incoming fetch event.

MozReview-Commit-ID: 3w5MNyhQNnd

--HG--
extra : rebase_source : 3228213d0ea6be1d23b9c49382f1f8d3c2f358f1

dom/workers/ServiceWorkerPrivate.cpp

@@ -1510,6 +1510,15 @@ public:
 
     if (mMarkLaunchServiceWorkerEnd) {
       mInterceptedChannel->SetLaunchServiceWorkerEnd(TimeStamp::Now());
+
+      // A probe to measure sw launch time for telemetry.
+      TimeStamp launchStartTime = TimeStamp();
+      mInterceptedChannel->GetLaunchServiceWorkerStart(&launchStartTime);
+
+      TimeStamp launchEndTime = TimeStamp();
+      mInterceptedChannel->GetLaunchServiceWorkerEnd(&launchEndTime);
+      Telemetry::AccumulateTimeDelta(Telemetry::SERVICE_WORKER_LAUNCH_TIME,
+                                     launchStartTime, launchEndTime);
     }
 
     mInterceptedChannel->SetDispatchFetchEventEnd(TimeStamp::Now());

netwerk/base/nsINetworkInterceptController.idl

@@ -107,9 +107,17 @@ interface nsIInterceptedChannel : nsISupports
     [noscript]
     void SetLaunchServiceWorkerStart(in TimeStamp aTimeStamp);
 
+    // A hack to get sw launch start time for telemetry.
+    [noscript]
+    void GetLaunchServiceWorkerStart(out TimeStamp aTimeStamp);
+
     [noscript]
     void SetLaunchServiceWorkerEnd(in TimeStamp aTimeStamp);
 
+    // A hack to get sw launch end time for telemetry.
+    [noscript]
+    void GetLaunchServiceWorkerEnd(out TimeStamp aTimeStamp);
+
     [noscript]
     void SetDispatchFetchEventStart(in TimeStamp aTimeStamp);
 

netwerk/protocol/http/InterceptedChannel.h

@@ -84,6 +84,14 @@ public:
     return NS_OK;
   }
 
+  NS_IMETHODIMP
+  GetLaunchServiceWorkerStart(TimeStamp* aTimeStamp) override
+  {
+    MOZ_DIAGNOSTIC_ASSERT(aTimeStamp);
+    *aTimeStamp = mLaunchServiceWorkerStart;
+    return NS_OK;
+  }
+
   NS_IMETHODIMP
   SetLaunchServiceWorkerEnd(TimeStamp aTimeStamp) override
   {
@@ -91,6 +99,14 @@ public:
     return NS_OK;
   }
 
+  NS_IMETHODIMP
+  GetLaunchServiceWorkerEnd(TimeStamp* aTimeStamp) override
+  {
+    MOZ_DIAGNOSTIC_ASSERT(aTimeStamp);
+    *aTimeStamp = mLaunchServiceWorkerEnd;
+    return NS_OK;
+  }
+
   NS_IMETHODIMP
   SetDispatchFetchEventStart(TimeStamp aTimeStamp) override
   {

toolkit/components/telemetry/Histograms.json

@@ -11048,6 +11048,17 @@
     "alert_emails": ["safebrowsing-telemetry@mozilla.org"],
     "bug_numbers": [1058133]
   },
+  "SERVICE_WORKER_LAUNCH_TIME": {
+    "record_in_processes": ["main", "content"],
+    "expires_in_version": "never",
+    "bug_numbers": [1328398],
+    "kind": "exponential",
+    "high": 5000,
+    "n_buckets": 25,
+    "releaseChannelCollection": "opt-out",
+    "alert_emails": ["sw-telemetry@mozilla.com", "ttung@mozilla.com"],
+    "description": "Time (ms) for a service worker to start up."
+  },
   "SERVICE_WORKER_REGISTRATION_LOADING": {
     "record_in_processes": ["main", "content"],
     "expires_in_version": "never",