Implement an atomic counter to log gauges

Author: tejasd

firebase-perf/src/main/java/com/google/firebase/perf/session/gauges/CpuGaugeCollector.java

@@ -76,7 +76,7 @@ public class CpuGaugeCollector {
   private final String procFileName;
   private final long clockTicksPerSecond;
 
-  @Nullable private ScheduledFuture cpuMetricCollectorJob = null;
+  @Nullable private ScheduledFuture<?> cpuMetricCollectorJob = null;
   private long cpuMetricCollectionRateMs = UNSET_CPU_METRIC_COLLECTION_RATE;
 
   // TODO(b/258263016): Migrate to go/firebase-android-executors
@@ -166,6 +166,7 @@ private synchronized void scheduleCpuMetricCollectionWithRate(
                 CpuMetricReading currCpuReading = syncCollectCpuMetric(referenceTime);
                 if (currCpuReading != null) {
                   cpuMetricReadings.add(currCpuReading);
+                  GaugeCounter.Companion.getInstance().incrementCounter();
                 }
               },
               /* initialDelay */ 0,

firebase-perf/src/main/java/com/google/firebase/perf/session/gauges/GaugeCounter.kt

@@ -0,0 +1,26 @@
+package com.google.firebase.perf.session.gauges
+
+import java.util.concurrent.atomic.AtomicInteger
+
+
+class GaugeCounter private constructor() {
+    private val counter = AtomicInteger(0)
+    private val gaugeManager: GaugeManager = GaugeManager.getInstance()
+
+    fun incrementCounter() {
+        val metricsCount = counter.incrementAndGet()
+
+        if (metricsCount >= MAX_METRIC_COUNT && gaugeManager.logGaugeMetrics()) {
+            counter.set(0)
+        }
+    }
+
+    fun resetCounter() {
+        counter.set(0)
+    }
+
+    companion object {
+        val instance: GaugeCounter by lazy(LazyThreadSafetyMode.SYNCHRONIZED) { GaugeCounter() }
+        const val MAX_METRIC_COUNT = 25
+    }
+}

firebase-perf/src/main/java/com/google/firebase/perf/session/gauges/GaugeManager.java

@@ -59,7 +59,6 @@ public class GaugeManager extends AppStateUpdateHandler {
   private final TransportManager transportManager;
 
   @Nullable private GaugeMetadataManager gaugeMetadataManager;
-  @Nullable private ScheduledFuture<?> gaugeManagerDataCollectionJob = null;
   @Nullable private PerfSession session = null;
   private ApplicationProcessState applicationProcessState =
       ApplicationProcessState.APPLICATION_PROCESS_STATE_UNKNOWN;
@@ -183,30 +182,36 @@ public void stopCollectingGauges() {
       return;
     }
 
-    // This is needed, otherwise the Runnable might use a stale value.
-    final String sessionIdForScheduledTask = session.sessionId();
-    final ApplicationProcessState applicationProcessStateForScheduledTask = applicationProcessState;
-
     cpuGaugeCollector.get().stopCollecting();
     memoryGaugeCollector.get().stopCollecting();
 
-    if (gaugeManagerDataCollectionJob != null) {
-      gaugeManagerDataCollectionJob.cancel(false);
+    logGaugeMetrics();
+    GaugeCounter.Companion.getInstance().resetCounter();
+    this.session = null;
+  }
+
+  protected boolean logGaugeMetrics() {
+    if (session == null) {
+      logger.warn("Attempted to log Gauge Metrics when session was null.");
+      return false;
     }
 
-    // Flush any data that was collected for this session one last time.
+    logExistingGaugeMetrics(session.sessionId(), applicationProcessState);
+    return true;
+  }
+
+  private void logExistingGaugeMetrics(String sessionId, ApplicationProcessState applicationProcessState) {
+    // Flush any data that was collected and attach it to the given session and app state.
     @SuppressWarnings("FutureReturnValueIgnored")
     ScheduledFuture<?> unusedFuture =
-        gaugeManagerExecutor
-            .get()
-            .schedule(
-                () -> {
-                  syncFlush(sessionIdForScheduledTask, applicationProcessStateForScheduledTask);
-                },
-                TIME_TO_WAIT_BEFORE_FLUSHING_GAUGES_QUEUE_MS,
-                TimeUnit.MILLISECONDS);
-
-    this.session = null;
+            gaugeManagerExecutor
+                    .get()
+                    .schedule(
+                            () -> {
+                              syncFlush(sessionId, applicationProcessState);
+                            },
+                            TIME_TO_WAIT_BEFORE_FLUSHING_GAUGES_QUEUE_MS,
+                            TimeUnit.MILLISECONDS);
   }
 
   /**

firebase-perf/src/main/java/com/google/firebase/perf/session/gauges/MemoryGaugeCollector.java

@@ -129,6 +129,7 @@ private synchronized void scheduleMemoryMetricCollectionWithRate(
                 AndroidMemoryReading memoryReading = syncCollectMemoryMetric(referenceTime);
                 if (memoryReading != null) {
                   memoryMetricReadings.add(memoryReading);
+                  GaugeCounter.Companion.getInstance().incrementCounter();
                 }
               },
               /* initialDelay */ 0,