Bug 1724686 - Add exposure ping to Nimbus platform API r=emilio,chutten

Differential Revision: https://phabricator.services.mozilla.com/D122235

toolkit/components/nimbus/lib/NimbusFeatures.cpp

@@ -5,9 +5,16 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "mozilla/browser/NimbusFeatures.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/dom/ScriptSettings.h"
+#include "jsapi.h"
+#include "js/JSON.h"
+#include "nsJSUtils.h"
 
 namespace mozilla {
 
+static nsTHashSet<nsCString> sExposureFeatureSet;
+
 void NimbusFeatures::GetPrefName(const nsACString& aFeatureId,
                                  const nsACString& aVariable,
                                  nsACString& aPref) {
@@ -16,8 +23,10 @@ void NimbusFeatures::GetPrefName(const nsACString& aFeatureId,
   aPref.Truncate();
   aPref.Append(kSyncDataPrefBranch);
   aPref.Append(aFeatureId);
-  aPref.Append(".");
-  aPref.Append(aVariable);
+  if (!aVariable.IsEmpty()) {
+    aPref.Append(".");
+    aPref.Append(aVariable);
+  }
 }
 
 bool NimbusFeatures::GetBool(const nsACString& aFeatureId,
@@ -52,4 +61,93 @@ nsresult NimbusFeatures::OffUpdate(const nsACString& aFeatureId,
   return Preferences::UnregisterCallback(aUserCallback, pref, aUserData);
 }
 
+/**
+ * Attempt to read Nimbus preference to determine experiment and branch slug.
+ * Nimbus will store a pref with experiment metadata in the following format:
+ * {
+ *   slug: "experiment slug",
+ *   branch: { slug: "branch slug" },
+ *   ...
+ * }
+ * The naming convention for preference names is:
+ * `nimbus.syncdatastore.<feature_id>`
+ * These values are used to send `exposure` telemetry pings.
+ */
+nsresult NimbusFeatures::GetExperimentSlug(const nsACString& aFeatureId,
+                                           nsACString& aExperimentSlug,
+                                           nsACString& aBranchSlug) {
+  nsAutoCString prefName;
+  nsAutoString prefValue;
+
+  aExperimentSlug.Truncate();
+  aBranchSlug.Truncate();
+
+  GetPrefName(aFeatureId, ""_ns, prefName);
+  MOZ_TRY(Preferences::GetString(prefName.get(), prefValue));
+  if (prefValue.IsEmpty()) {
+    return NS_ERROR_UNEXPECTED;
+  }
+  dom::AutoJSAPI jsapi;
+  if (!jsapi.Init(xpc::PrivilegedJunkScope())) {
+    return NS_ERROR_UNEXPECTED;
+  }
+  JSContext* cx = jsapi.cx();
+  JS::Rooted<JS::Value> json(cx, JS::NullValue());
+  if (JS_ParseJSON(cx, prefValue.BeginReading(), prefValue.Length(), &json) &&
+      json.isObject()) {
+    JS::Rooted<JSObject*> experimentJSON(cx, json.toObjectOrNull());
+    JS::RootedValue expSlugValue(cx);
+    if (!JS_GetProperty(cx, experimentJSON, "slug", &expSlugValue)) {
+      return NS_ERROR_UNEXPECTED;
+    }
+    AssignJSString(cx, aExperimentSlug, expSlugValue.toString());
+
+    JS::RootedValue branchJSON(cx);
+    if (!JS_GetProperty(cx, experimentJSON, "branch", &branchJSON) &&
+        !branchJSON.isObject()) {
+      return NS_ERROR_UNEXPECTED;
+    }
+    JS::Rooted<JSObject*> branchObj(cx, branchJSON.toObjectOrNull());
+    JS::RootedValue branchSlugValue(cx);
+    if (!JS_GetProperty(cx, branchObj, "slug", &branchSlugValue)) {
+      return NS_ERROR_UNEXPECTED;
+    }
+    AssignJSString(cx, aBranchSlug, branchSlugValue.toString());
+  }
+
+  return NS_OK;
+}
+
+/**
+ * Sends an exposure event for aFeatureId when enrolled in an experiment.
+ * By default we only attempt to send once. For some usecases it might be useful
+ * to send multiple times or retry to send (when for example we are enrolled
+ * after the first call to this function) in which case set the optional
+ * aForce to `true`.
+ */
+nsresult NimbusFeatures::RecordExposureEvent(const nsACString& aFeatureId,
+                                             const bool aForce) {
+  nsAutoCString featureName(aFeatureId);
+  if (!sExposureFeatureSet.EnsureInserted(featureName) && !aForce) {
+    // We already sent (or tried to send) an exposure ping for this featureId
+    return NS_ERROR_ABORT;
+  }
+  nsAutoCString slugName;
+  nsAutoCString branchName;
+  MOZ_TRY(GetExperimentSlug(aFeatureId, slugName, branchName));
+  if (slugName.IsEmpty() || branchName.IsEmpty()) {
+    // Failed getting experiment metadata or not enrolled in an experiment for
+    // this featureId
+    return NS_ERROR_UNEXPECTED;
+  }
+  Telemetry::SetEventRecordingEnabled("normandy"_ns, true);
+  nsTArray<Telemetry::EventExtraEntry> extra(2);
+  extra.AppendElement(Telemetry::EventExtraEntry{"branchSlug"_ns, branchName});
+  extra.AppendElement(Telemetry::EventExtraEntry{"featureId"_ns, featureName});
+  Telemetry::RecordEvent(Telemetry::EventID::Normandy_Expose_NimbusExperiment,
+                         Some(slugName), Some(std::move(extra)));
+
+  return NS_OK;
+}
+
 }  // namespace mozilla

toolkit/components/nimbus/lib/NimbusFeatures.h

@@ -8,6 +8,7 @@
 #define mozilla_NimbusFeatures_h
 
 #include "mozilla/Preferences.h"
+#include "nsTHashSet.h"
 
 namespace mozilla {
 
@@ -16,6 +17,10 @@ class NimbusFeatures {
   static void GetPrefName(const nsACString& aFeatureId,
                           const nsACString& aVariable, nsACString& aPref);
 
+  static nsresult GetExperimentSlug(const nsACString& aFeatureId,
+                                    nsACString& aExperimentSlug,
+                                    nsACString& aBranchSlug);
+
  public:
   static bool GetBool(const nsACString& aFeatureId, const nsACString& aVariable,
                       bool aDefault);
@@ -30,6 +35,9 @@ class NimbusFeatures {
   static nsresult OffUpdate(const nsACString& aFeatureId,
                             const nsACString& aVariable,
                             PrefChangedFunc aUserCallback, void* aUserData);
+
+  static nsresult RecordExposureEvent(const nsACString& aFeatureId,
+                                      const bool aForce = false);
 };
 
 }  // namespace mozilla

toolkit/components/nimbus/test/gtest/NimbusFeatures_RecordExposure.cpp

@@ -0,0 +1,44 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "gtest/gtest.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/browser/NimbusFeatures.h"
+#include "js/Array.h"
+#include "js/PropertyAndElement.h"
+#include "js/TypeDecls.h"
+#include "TelemetryFixture.h"
+#include "TelemetryTestHelpers.h"
+
+using namespace mozilla;
+using namespace TelemetryTestHelpers;
+
+class NimbusTelemetryFixture : public TelemetryTestFixture {};
+
+TEST_F(NimbusTelemetryFixture, NimbusFeaturesTelemetry) {
+  constexpr auto prefName = "nimbus.syncdatastore.foo"_ns;
+  constexpr auto prefValue =
+      R"({"slug":"experiment-slug","branch":{"slug":"branch-slug"}})";
+  AutoJSContextWithGlobal cx(mCleanGlobal);
+  Unused << mTelemetry->ClearEvents();
+
+  ASSERT_EQ(NimbusFeatures::RecordExposureEvent("foo"_ns), NS_ERROR_UNEXPECTED)
+      << "Should fail because not enrolled in experiment";
+  // Set the experiment info for `foo`
+  Preferences::SetCString(prefName.get(), prefValue);
+  ASSERT_EQ(NimbusFeatures::RecordExposureEvent("foo"_ns), NS_ERROR_ABORT)
+      << "Should fail even though enrolled because this is the 2nd call";
+  ASSERT_EQ(NimbusFeatures::RecordExposureEvent("foo"_ns, true), NS_OK)
+      << "Should work because we set aForce=true";
+  ASSERT_EQ(NimbusFeatures::RecordExposureEvent("bar"_ns), NS_ERROR_UNEXPECTED)
+      << "Should fail because we don't have an experiment for bar";
+  ASSERT_EQ(NimbusFeatures::RecordExposureEvent("foo"_ns), NS_ERROR_ABORT)
+      << "Should abort because we've already send exposure for this featureId";
+  JS::RootedValue eventsSnapshot(cx.GetJSContext());
+  GetEventSnapshot(cx.GetJSContext(), &eventsSnapshot);
+  ASSERT_TRUE(EventPresent(cx.GetJSContext(), eventsSnapshot, "normandy"_ns,
+                           "expose"_ns, "nimbus_experiment"_ns));
+}

toolkit/components/nimbus/test/gtest/moz.build

@@ -6,6 +6,11 @@
 
 UNIFIED_SOURCES += [
     "NimbusFeatures_GetTest.cpp",
+    "NimbusFeatures_RecordExposure.cpp",
+]
+
+LOCAL_INCLUDES += [
+    "/toolkit/components/telemetry/tests/gtest",
 ]
 
 FINAL_LIBRARY = "xul-gtest"