Add more legacy session verification, move up gauge collection, and update comments.

firebase-perf/src/main/java/com/google/firebase/perf/logging/FirebaseSessionsEnforcementCheck.kt

@@ -18,17 +18,28 @@ package com.google.firebase.perf.logging
 
 import com.google.firebase.perf.session.PerfSession
 import com.google.firebase.perf.session.isLegacy
+import com.google.firebase.perf.v1.PerfSession as ProtoPerfSession
 
 class FirebaseSessionsEnforcementCheck {
   companion object {
     /** When enabled, failed preconditions will cause assertion errors for debugging. */
     @JvmStatic var enforcement: Boolean = false
     private var logger: AndroidLogger = AndroidLogger.getInstance()
 
+    @JvmStatic
+    fun checkSession(sessions: List<ProtoPerfSession>, failureMessage: String) {
+      sessions.forEach { checkSession(it.sessionId, failureMessage) }
+    }
+
     @JvmStatic
     fun checkSession(session: PerfSession, failureMessage: String) {
-      if (session.isLegacy()) {
-        logger.debug("legacy session ${session.sessionId()}: $failureMessage")
+      checkSession(session.sessionId(), failureMessage)
+    }
+
+    @JvmStatic
+    fun checkSession(sessionId: String, failureMessage: String) {
+      if (sessionId.isLegacy()) {
+        logger.debug("legacy session ${sessionId}: $failureMessage")
         assert(!enforcement) { failureMessage }
       }
     }

firebase-perf/src/main/java/com/google/firebase/perf/session/SessionManager.java

@@ -52,7 +52,8 @@ public final PerfSession perfSession() {
   }
 
   private SessionManager() {
-    // session should quickly updated by session subscriber.
+    // Creates a legacy session by default. This is a safety net to allow initializing
+    // SessionManager - but the current implementation replaces it immediately.
     this(GaugeManager.getInstance(), PerfSession.createWithId(null));
     FirebaseSessionsEnforcementCheck.checkSession(perfSession, "SessionManager()");
   }
@@ -101,7 +102,11 @@ public void updatePerfSession(PerfSession perfSession) {
 
     this.perfSession = perfSession;
 
-    // TODO(b/394127311): Update/verify behavior for Firebase Sessions.
+    // Start or stop the gauge data collection ASAP.
+    startOrStopCollectingGauges();
+
+    // Log gauge metadata.
+    logGaugeMetadataIfCollectionEnabled();
 
     synchronized (clients) {
       for (Iterator<WeakReference<SessionAwareObject>> i = clients.iterator(); i.hasNext(); ) {
@@ -115,12 +120,6 @@ public void updatePerfSession(PerfSession perfSession) {
         }
       }
     }
-
-    // Log gauge metadata.
-    logGaugeMetadataIfCollectionEnabled();
-
-    // Start of stop the gauge data collection.
-    startOrStopCollectingGauges();
   }
 
   /**
@@ -129,6 +128,7 @@ public void updatePerfSession(PerfSession perfSession) {
    * PerfSession} was already initialized a moment ago by getInstance(). Unlike updatePerfSession,
    * this does not reset the perfSession.
    */
+  @Deprecated // TODO(b/394127311): Delete this. AQS early initialization updates the session ASAP.
   public void initializeGaugeCollection() {
     startOrStopCollectingGauges();
   }

firebase-perf/src/main/java/com/google/firebase/perf/transport/TransportManager.java

@@ -39,6 +39,7 @@
 import com.google.firebase.perf.config.ConfigResolver;
 import com.google.firebase.perf.logging.AndroidLogger;
 import com.google.firebase.perf.logging.ConsoleUrlGenerator;
+import com.google.firebase.perf.logging.FirebaseSessionsEnforcementCheck;
 import com.google.firebase.perf.metrics.validator.PerfMetricValidator;
 import com.google.firebase.perf.session.SessionManager;
 import com.google.firebase.perf.util.Constants;
@@ -299,6 +300,8 @@ public void log(final TraceMetric traceMetric) {
    * {@link #isAllowedToDispatch(PerfMetric)}).
    */
   public void log(final TraceMetric traceMetric, final ApplicationProcessState appState) {
+    FirebaseSessionsEnforcementCheck.checkSession(
+        traceMetric.getPerfSessionsList(), "log TraceMetric");
     executorService.execute(
         () -> syncLog(PerfMetric.newBuilder().setTraceMetric(traceMetric), appState));
   }
@@ -327,6 +330,8 @@ public void log(final NetworkRequestMetric networkRequestMetric) {
    */
   public void log(
       final NetworkRequestMetric networkRequestMetric, final ApplicationProcessState appState) {
+    FirebaseSessionsEnforcementCheck.checkSession(
+        networkRequestMetric.getPerfSessionsList(), "log NetworkRequestMetric");
     executorService.execute(
         () ->
             syncLog(
@@ -356,6 +361,7 @@ public void log(final GaugeMetric gaugeMetric) {
    * {@link #isAllowedToDispatch(PerfMetric)}).
    */
   public void log(final GaugeMetric gaugeMetric, final ApplicationProcessState appState) {
+    FirebaseSessionsEnforcementCheck.checkSession(gaugeMetric.getSessionId(), "log GaugeMetric");
     executorService.execute(
         () -> syncLog(PerfMetric.newBuilder().setGaugeMetric(gaugeMetric), appState));
   }