Add no-op experiment to test service-experiments integration (#4551)

* Add no-op experiment to test service-experiments integration

* Shorten metric name to meet schema

* Add active_experiment metric to docs

* Add approved data review

app/metrics.yaml

@@ -907,6 +907,7 @@ history:
     notification_emails:
       - fenix-core@mozilla.com
     expires: "2020-03-01"
+
 reader_mode:
   available:
     type: event
@@ -1112,4 +1113,21 @@ collections:
       - https://github.com/mozilla-mobile/fenix/pull/4539
     notification_emails:
       - fenix-core@mozilla.com
-    expires: "2020-03-01"
+    expires: "2020-03-01"
+
+experiments.metrics:
+  active_experiment:
+    type: string
+    description: >
+      Records the branch name of the active experiment, if the client is enrolled in the
+      `fenix-test-2019-08-05` experiment. This is intended to validate that the service-experiments
+      library properly matches clients to experiments and can take action based on a multi-branched
+      experiment. This is done by recording the experiment branch name in this string metric which
+      allows the experiment to be transparent and unobtrusive to the user.
+    bugs:
+      - 1543986
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1543986#c4
+    notification_emails:
+      - mcooper@mozilla.com
+    expires: 2019-11-01

app/src/main/java/org/mozilla/fenix/FenixApplication.kt

@@ -31,6 +31,7 @@ import mozilla.components.support.rusthttp.RustHttpConfig
 import mozilla.components.support.rustlog.RustLog
 import org.mozilla.fenix.components.Components
 import org.mozilla.fenix.utils.Settings
+import org.mozilla.fenix.GleanMetrics.ExperimentsMetrics
 import java.io.File
 
 @SuppressLint("Registered")
@@ -80,6 +81,16 @@ open class FenixApplication : Application() {
             )
         )
 
+        // When the `fenix-test-2019-08-05` experiment is active, record its branch in Glean
+        // telemetry. This will be used to validate that the experiment system correctly enrolls
+        // clients and segments them into branches. Note that this will not take effect the first
+        // time the application has launched, since there won't be enough time for the experiments
+        // library to get a list of experiments. It will take effect the second time the
+        // application is launched.
+        Experiments.withExperiment("fenix-test-2019-08-05") { branchName ->
+            ExperimentsMetrics.activeExperiment.set(branchName)
+        }
+
         setupLeakCanary()
         if (Settings.getInstance(this).isTelemetryEnabled) {
             components.analytics.metrics.start()

docs/metrics.md

@@ -8,7 +8,7 @@
         <th>key</th>
         <th>type</th>
         <th>description</th>
-        <th>data deview</th>
+        <th>data review</th>
         <th>extras</th>
         <th>expires</th>
     </tr>
@@ -1057,5 +1057,13 @@ Data that is sent in the activation ping
         <td></td>
         <td>2019-10-01</td>
     </tr>
+    <tr>
+        <td>active_experiment</td>
+        <td>string</td>
+        <td>The branch name of the active experiment, if the client is enrolled in the `fenix-test-2019-08-05` experiment.</td>
+        <td><a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1543986#c4">link</a></td>
+        <td></td>
+        <td>2019-11-01</td>
+    </tr>
 </table>
 </pre>