For #10434: Handle cases when proc/$pid/stat is not accessible.

app/metrics.yaml

@@ -2253,6 +2253,22 @@ startup.timeline:
       - perf-android-fe@mozilla.com
       - mcomella@mozilla.com
     expires: "2020-07-15"
+  framework_start_read_error:
+    send_in_pings:
+      - startup-timeline
+    type: boolean
+    description: |
+      An error when attempting to read stats from /proc pseudo-filesystem -
+      privacy managers can block access to reading these files -
+      the application will catch a file reading exception.
+    bugs:
+      - https://github.com/mozilla-mobile/fenix/issues/10434
+    data_reviews:
+      - https://github.com/mozilla-mobile/fenix/pull/10481
+    notification_emails:
+      - perf-android-fe@mozilla.com
+      - mcomella@mozilla.com
+    expires: "2020-07-15"
   clock_ticks_per_second:
     send_in_pings:
       - startup-timeline

app/src/main/java/org/mozilla/fenix/perf/StartupFrameworkStartMeasurement.kt

@@ -6,6 +6,7 @@ package org.mozilla.fenix.perf
 
 import android.os.Process
 import android.os.SystemClock
+import java.io.FileNotFoundException
 import kotlin.math.roundToLong
 import org.mozilla.fenix.GleanMetrics.StartupTimeline as Telemetry
 
@@ -53,14 +54,23 @@ internal class StartupFrameworkStartMeasurement(
         if (applicationInitNanos < 0) {
             telemetry.frameworkStartError.set(true)
         } else {
-            telemetry.frameworkStart.setRawNanos(getFrameworkStartNanos())
+            try {
+                telemetry.frameworkStart.setRawNanos(getFrameworkStartNanos())
+            } catch (e: FileNotFoundException) {
+                // Privacy managers can add hooks that block access to reading system /proc files.
+                // We want to catch these exception and report an error on accessing the file
+                // rather than an implementation error.
+                telemetry.frameworkStartReadError.set(true)
+            }
 
             // frameworkStart is derived from the number of clock ticks per second. To ensure this
             // value does not throw off our result, we capture it too.
             telemetry.clockTicksPerSecond.add(stat.clockTicksPerSecond.toInt())
         }
     }
-
+    /**
+     * @throws [java.io.FileNotFoundException]
+     */
     private fun getFrameworkStartNanos(): Long {
         // Get our timestamps in ticks: we expect ticks to be less granular than nanoseconds so,
         // to ensure our measurement uses the correct number of significant figures, we convert

app/src/main/java/org/mozilla/fenix/perf/Stat.kt

@@ -24,6 +24,9 @@ private const val FIELD_POS_STARTTIME = 21 // starttime naming matches field in
  */
 open class Stat {
 
+    /**
+     * @throws [java.io.FileNotFoundException]
+     */
     @VisibleForTesting(otherwise = PRIVATE)
     open fun getStatText(pid: Int): String = File("/proc/$pid/stat").readText()
 

docs/metrics.md

@@ -275,6 +275,7 @@ The following metrics are added to the ping:
 | startup.timeline.clock_ticks_per_second |[counter](https://mozilla.github.io/glean/book/user/metrics/counter.html) |The number of clock tick time units that occur in one second on this particular device. This value is expected to be used in conjunction with the `framework_start` metric.  |[1](https://github.com/mozilla-mobile/fenix/pull/9788#pullrequestreview-394228626)||2020-07-15 |
 | startup.timeline.framework_start |[timespan](https://mozilla.github.io/glean/book/user/metrics/timespan.html) |The duration the Android framework takes to start before letting us run code in `*Application.init`. This is calculated from `appInitTimestamp - processStartTimestamp`. `processStartTimestamp` is derived from the clock tick time unit, which is expected to be less granular than nanoseconds. Therefore, we convert and round our timestamps to clock ticks before computing the difference and convert back to nanoseconds to report.  For debugging purposes, `clock_ticks_per_second`, which may vary between devices, is also reported as a metric  |[1](https://github.com/mozilla-mobile/fenix/pull/9788#pullrequestreview-394228626)||2020-07-15 |
 | startup.timeline.framework_start_error |[boolean](https://mozilla.github.io/glean/book/user/metrics/boolean.html) |An error when attempting to record `framework_start` - the application init timestamp returned a negative value - which is likely indicative of a bug in the implementation.  |[1](https://github.com/mozilla-mobile/fenix/pull/9788#pullrequestreview-394228626)||2020-07-15 |
+| startup.timeline.framework_start_read_error |[boolean](https://mozilla.github.io/glean/book/user/metrics/boolean.html) |An error when attempting to read stats from /proc pseudo-filesystem - privacy managers can block access to reading these files - the application will catch a file reading exception.  |[1](https://github.com/mozilla-mobile/fenix/pull/10481)||2020-07-15 |
 
 
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