Issue #12731: Collect telemetry about the content process of tabs getting killed.

app/metrics.yaml

@@ -4402,3 +4402,55 @@ contextual_menu:
     notification_emails:
       - fenix-core@mozilla.com
     expires: "2021-06-01"
+
+engine:
+  tab_kills:
+    type: labeled_counter
+    labels:
+      - foreground
+      - background
+    description: |
+      How often was the content process of a foreground (selected) or
+      background tab killed.
+    bugs:
+      - https://github.com/mozilla-mobile/android-components/issues/9366
+    data_reviews:
+      - https://github.com/mozilla-mobile/fenix/pull/17864
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - fenix-core@mozilla.com
+      - skaspari@mozilla.com
+    expires: "2021-12-31"
+  kill_foreground_age:
+    type: timespan
+    time_unit: millisecond
+    description: |
+      Measures the age of the engine session of a foreground (selected) tab
+      at the time its content process got killed.
+    bugs:
+      - https://github.com/mozilla-mobile/android-components/issues/9366
+    data_reviews:
+      - TBD
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - fenix-core@mozilla.com
+      - skaspari@mozilla.com
+    expires: "2021-12-31"
+  kill_background_age:
+    type: timespan
+    time_unit: millisecond
+    description: |
+      Measures the age of the engine session of a background tab at the
+      time its content process got killed.
+    bugs:
+      - https://github.com/mozilla-mobile/android-components/issues/9366
+    data_reviews:
+      - https://github.com/mozilla-mobile/fenix/pull/17864
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - fenix-core@mozilla.com
+      - skaspari@mozilla.com
+    expires: "2021-12-31"

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

@@ -8,17 +8,23 @@ import androidx.annotation.VisibleForTesting
 import mozilla.components.browser.state.action.BrowserAction
 import mozilla.components.browser.state.action.ContentAction
 import mozilla.components.browser.state.action.DownloadAction
+import mozilla.components.browser.state.action.EngineAction
 import mozilla.components.browser.state.action.TabListAction
 import mozilla.components.browser.state.selector.findTab
+import mozilla.components.browser.state.selector.findTabOrCustomTab
 import mozilla.components.browser.state.selector.normalTabs
 import mozilla.components.browser.state.state.BrowserState
+import mozilla.components.browser.state.state.EngineState
+import mozilla.components.browser.state.state.SessionState
 import mozilla.components.lib.state.Middleware
 import mozilla.components.lib.state.MiddlewareContext
+import mozilla.components.support.base.android.Clock
 import mozilla.components.support.base.log.logger.Logger
 import org.mozilla.fenix.components.metrics.Event
 import org.mozilla.fenix.components.metrics.MetricController
 import org.mozilla.fenix.search.telemetry.ads.AdsTelemetry
 import org.mozilla.fenix.utils.Settings
+import org.mozilla.fenix.GleanMetrics.Engine as EngineMetrics
 
 /**
  * [Middleware] to record telemetry in response to [BrowserAction]s.
@@ -90,6 +96,10 @@ class TelemetryMiddleware(
             is DownloadAction.AddDownloadAction -> {
                 metrics.track(Event.DownloadAdded)
             }
+            is EngineAction.KillEngineSessionAction -> {
+                val tab = context.state.findTabOrCustomTab(action.sessionId)
+                onEngineSessionKilled(context.state, tab)
+            }
         }
 
         next(action)
@@ -112,4 +122,36 @@ class TelemetryMiddleware(
             }
         }
     }
+
+    /**
+     * Collecting some engine-specific (GeckoView) telemetry.
+     * https://github.com/mozilla-mobile/android-components/issues/9366
+     */
+    private fun onEngineSessionKilled(state: BrowserState, tab: SessionState?) {
+        if (tab == null) {
+            logger.debug("Could not find tab for killed engine session")
+            return
+        }
+
+        val isSelected = tab.id == state.selectedTabId
+        val ageNanos = tab.engineState.ageNanos()
+
+        // Increment the counter of killed foreground/background tabs
+        val tabKillLabel = if (isSelected) { "foreground" } else { "background" }
+        EngineMetrics.tabKills[tabKillLabel].add()
+
+        // Record the age of the engine session of the killed foreground/background tab.
+        if (isSelected && ageNanos != null) {
+            EngineMetrics.killForegroundAge.setRawNanos(ageNanos)
+        } else if (ageNanos != null) {
+            EngineMetrics.killBackgroundAge.setRawNanos(ageNanos)
+        }
+    }
+}
+
+@Suppress("MagicNumber")
+private fun EngineState.ageNanos(): Long? {
+    val timestamp = (timestamp ?: return null)
+    val now = Clock.elapsedRealtime()
+    return (now - timestamp) * 1_000_000
 }

app/src/test/java/org/mozilla/fenix/TelemetryMiddlewareTest.kt

@@ -4,20 +4,28 @@
 
 package org.mozilla.fenix
 
+import androidx.test.core.app.ApplicationProvider
 import io.mockk.mockk
 import io.mockk.verify
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.test.TestCoroutineDispatcher
+import mozilla.components.browser.session.engine.EngineMiddleware
 import mozilla.components.browser.state.action.ContentAction
 import mozilla.components.browser.state.action.DownloadAction
+import mozilla.components.browser.state.action.EngineAction
 import mozilla.components.browser.state.action.TabListAction
+import mozilla.components.browser.state.state.BrowserState
 import mozilla.components.browser.state.state.LoadRequestState
 import mozilla.components.browser.state.state.createTab
 import mozilla.components.browser.state.store.BrowserStore
+import mozilla.components.service.glean.testing.GleanTestRule
+import mozilla.components.support.base.android.Clock
 import mozilla.components.support.test.ext.joinBlocking
 import mozilla.components.support.test.mock
 import mozilla.components.support.test.robolectric.testContext
 import mozilla.components.support.test.rule.MainCoroutineRule
+import org.junit.After
+import org.junit.Assert
 import org.junit.Assert.assertEquals
 import org.junit.Assert.assertNotNull
 import org.junit.Assert.assertNull
@@ -30,6 +38,7 @@ import org.mozilla.fenix.components.metrics.MetricController
 import org.mozilla.fenix.helpers.FenixRobolectricTestRunner
 import org.mozilla.fenix.search.telemetry.ads.AdsTelemetry
 import org.mozilla.fenix.utils.Settings
+import org.mozilla.fenix.GleanMetrics.Engine as EngineMetrics
 
 @RunWith(FenixRobolectricTestRunner::class)
 @ExperimentalCoroutinesApi
@@ -45,8 +54,15 @@ class TelemetryMiddlewareTest {
     @get:Rule
     val coroutinesTestRule = MainCoroutineRule(testDispatcher)
 
+    @get:Rule
+    val gleanRule = GleanTestRule(ApplicationProvider.getApplicationContext())
+
+    private val clock = FakeClock()
+
     @Before
     fun setUp() {
+        Clock.delegate = clock
+
         settings = Settings(testContext)
         metrics = mockk(relaxed = true)
         adsTelemetry = mockk()
@@ -55,7 +71,15 @@ class TelemetryMiddlewareTest {
             adsTelemetry,
             metrics
         )
-        store = BrowserStore(middleware = listOf(telemetryMiddleware))
+        store = BrowserStore(
+            middleware = listOf(telemetryMiddleware) + EngineMiddleware.create(engine = mockk(), sessionLookup = { null }),
+            initialState = BrowserState()
+        )
+    }
+
+    @After
+    fun tearDown() {
+        Clock.reset()
     }
 
     @Test
@@ -244,4 +268,125 @@ class TelemetryMiddlewareTest {
 
         verify { metrics.track(Event.DownloadAdded) }
     }
+
+    @Test
+    fun `WHEN foreground tab getting killed THEN middleware counts it`() {
+        store.dispatch(TabListAction.RestoreAction(
+            listOf(
+                createTab("https://www.mozilla.org", id = "foreground"),
+                createTab("https://getpocket.com", id = "background_pocket"),
+                createTab("https://theverge.com", id = "background_verge")
+            ),
+            selectedTabId = "foreground"
+        )).joinBlocking()
+
+        Assert.assertFalse(EngineMetrics.tabKills["foreground"].testHasValue())
+        Assert.assertFalse(EngineMetrics.tabKills["background"].testHasValue())
+
+        store.dispatch(
+            EngineAction.KillEngineSessionAction("foreground")
+        ).joinBlocking()
+
+        Assert.assertTrue(EngineMetrics.tabKills["foreground"].testHasValue())
+    }
+
+    @Test
+    fun `WHEN background tabs getting killed THEN middleware counts it`() {
+        store.dispatch(TabListAction.RestoreAction(
+            listOf(
+                createTab("https://www.mozilla.org", id = "foreground"),
+                createTab("https://getpocket.com", id = "background_pocket"),
+                createTab("https://theverge.com", id = "background_verge")
+            ),
+            selectedTabId = "foreground"
+        )).joinBlocking()
+
+        Assert.assertFalse(EngineMetrics.tabKills["foreground"].testHasValue())
+        Assert.assertFalse(EngineMetrics.tabKills["background"].testHasValue())
+
+        store.dispatch(
+            EngineAction.KillEngineSessionAction("background_pocket")
+        ).joinBlocking()
+
+        Assert.assertFalse(EngineMetrics.tabKills["foreground"].testHasValue())
+        Assert.assertTrue(EngineMetrics.tabKills["background"].testHasValue())
+        assertEquals(1, EngineMetrics.tabKills["background"].testGetValue())
+
+        store.dispatch(
+            EngineAction.KillEngineSessionAction("background_verge")
+        ).joinBlocking()
+
+        Assert.assertFalse(EngineMetrics.tabKills["foreground"].testHasValue())
+        Assert.assertTrue(EngineMetrics.tabKills["background"].testHasValue())
+        assertEquals(2, EngineMetrics.tabKills["background"].testGetValue())
+    }
+
+    @Test
+    fun `WHEN foreground tab gets killed THEN middleware records foreground age`() {
+        store.dispatch(TabListAction.RestoreAction(
+            listOf(
+                createTab("https://www.mozilla.org", id = "foreground"),
+                createTab("https://getpocket.com", id = "background_pocket"),
+                createTab("https://theverge.com", id = "background_verge")
+            ),
+            selectedTabId = "foreground"
+        )).joinBlocking()
+
+        clock.elapsedTime = 100
+
+        store.dispatch(EngineAction.LinkEngineSessionAction(
+            sessionId = "foreground",
+            engineSession = mock()
+        )).joinBlocking()
+
+        Assert.assertFalse(EngineMetrics.killForegroundAge.testHasValue())
+        Assert.assertFalse(EngineMetrics.killBackgroundAge.testHasValue())
+
+        clock.elapsedTime = 500
+
+        store.dispatch(
+            EngineAction.KillEngineSessionAction("foreground")
+        ).joinBlocking()
+
+        Assert.assertTrue(EngineMetrics.killForegroundAge.testHasValue())
+        Assert.assertFalse(EngineMetrics.killBackgroundAge.testHasValue())
+        assertEquals(400, EngineMetrics.killForegroundAge.testGetValue())
+    }
+
+    @Test
+    fun `WHEN background tab gets killed THEN middleware records background age`() {
+        store.dispatch(TabListAction.RestoreAction(
+            listOf(
+                createTab("https://www.mozilla.org", id = "foreground"),
+                createTab("https://getpocket.com", id = "background_pocket"),
+                createTab("https://theverge.com", id = "background_verge")
+            ),
+            selectedTabId = "foreground"
+        )).joinBlocking()
+
+        clock.elapsedTime = 100
+
+        store.dispatch(EngineAction.LinkEngineSessionAction(
+            sessionId = "background_pocket",
+            engineSession = mock()
+        )).joinBlocking()
+
+        clock.elapsedTime = 700
+
+        Assert.assertFalse(EngineMetrics.killForegroundAge.testHasValue())
+        Assert.assertFalse(EngineMetrics.killBackgroundAge.testHasValue())
+
+        store.dispatch(
+            EngineAction.KillEngineSessionAction("background_pocket")
+        ).joinBlocking()
+
+        Assert.assertTrue(EngineMetrics.killBackgroundAge.testHasValue())
+        Assert.assertFalse(EngineMetrics.killForegroundAge.testHasValue())
+        assertEquals(600, EngineMetrics.killBackgroundAge.testGetValue())
+    }
+}
+
+private class FakeClock : Clock.Delegate {
+    var elapsedTime: Long = 0
+    override fun elapsedRealtime(): Long = elapsedTime
 }

docs/metrics.md

@@ -280,6 +280,9 @@ The following metrics are added to the ping:
 | browser.search.ad_clicks |[labeled_counter](https://mozilla.github.io/glean/book/user/metrics/labeled_counters.html) |Records clicks of adverts on SERP pages. The key format is ‘<provider-name>’.  |[1](https://github.com/mozilla-mobile/fenix/pull/10112), [2](https://github.com/mozilla-mobile/fenix/pull/15713#issuecomment-703972068)||2021-08-01 |2 |
 | browser.search.in_content |[labeled_counter](https://mozilla.github.io/glean/book/user/metrics/labeled_counters.html) |Records the type of interaction a user has on SERP pages.  |[1](https://github.com/mozilla-mobile/fenix/pull/10167), [2](https://github.com/mozilla-mobile/fenix/pull/15713#issuecomment-703972068)||2021-08-01 |2 |
 | browser.search.with_ads |[labeled_counter](https://mozilla.github.io/glean/book/user/metrics/labeled_counters.html) |Records counts of SERP pages with adverts displayed. The key format is ‘<provider-name>’.  |[1](https://github.com/mozilla-mobile/fenix/pull/10112), [2](https://github.com/mozilla-mobile/fenix/pull/15713#issuecomment-703972068)||2021-08-01 |2 |
+| engine.kill_background_age |[timespan](https://mozilla.github.io/glean/book/user/metrics/timespan.html) |Measures the age of the engine session of a background tab at the time its content process got killed.  |[1](https://github.com/mozilla-mobile/fenix/pull/17864)||2021-12-31 |1 |
+| engine.kill_foreground_age |[timespan](https://mozilla.github.io/glean/book/user/metrics/timespan.html) |Measures the age of the engine session of a foreground (selected) tab at the time its content process got killed.  |[1](TBD)||2021-12-31 |1 |
+| engine.tab_kills |[labeled_counter](https://mozilla.github.io/glean/book/user/metrics/labeled_counters.html) |How often was the content process of a foreground (selected) or background tab killed.  |[1](https://github.com/mozilla-mobile/fenix/pull/17864)|<ul><li>foreground</li><li>background</li></ul>|2021-12-31 |1 |
 | events.total_uri_count |[counter](https://mozilla.github.io/glean/book/user/metrics/counter.html) |A counter of URIs visited by the user in the current session, including page reloads. This does not include background page requests and URIs from embedded pages or private browsing but may be incremented without user interaction by website scripts that programmatically redirect to a new location.  |[1](https://github.com/mozilla-mobile/fenix/pull/1785), [2](https://github.com/mozilla-mobile/fenix/pull/8314), [3](https://github.com/mozilla-mobile/fenix/pull/15713#issuecomment-703972068)||2021-08-01 |2 |
 | metrics.adjust_ad_group |[string](https://mozilla.github.io/glean/book/user/metrics/string.html) |A string containing the Adjust ad group ID from which the user installed Fenix. This will not send on the first session the user runs. If the install is organic, this will be empty.  |[1](https://github.com/mozilla-mobile/fenix/pull/9253), [2](https://github.com/mozilla-mobile/fenix/pull/15713#issuecomment-703972068)||2021-08-01 |2 |
 | metrics.adjust_campaign |[string](https://mozilla.github.io/glean/book/user/metrics/string.html) |A string containing the Adjust campaign ID from which the user installed Fenix. This will not send on the first session the user runs. If the install is organic, this will be empty.  |[1](https://github.com/mozilla-mobile/fenix/pull/5579), [2](https://github.com/mozilla-mobile/fenix/pull/15713#issuecomment-703972068)||2021-08-01 |1 |