Change WithinAppServiceConnection's ScheduledThreadPoolExecutor's con… (#6414)

…figuration to avoid polling.

* Changed WithinAppServiceConnection's ScheduledThreadPoolExecutor's
configuration to allow the thread to stop polling after the timeout task
has been canceled.

Author: gsakakihara

firebase-messaging/CHANGELOG.md

@@ -2,6 +2,9 @@
 * [deprecated] Deprecated additional FCM upstream messaging methods. See the
   [FAQ](https://firebase.google.com/support/faq#fcm-23-deprecation) for more
   details.
+* [changed] Changed WithinAppServiceConnection's ScheduledThreadPoolExecutor's
+  configuration to allow the thread to stop polling after the timeout task has
+  been canceled.
 
 
 # 24.0.3

firebase-messaging/src/main/java/com/google/firebase/messaging/WithinAppServiceConnection.java

@@ -14,6 +14,7 @@
 package com.google.firebase.messaging;
 
 import static com.google.firebase.messaging.FirebaseMessaging.TAG;
+import static java.util.concurrent.TimeUnit.SECONDS;
 
 import android.annotation.SuppressLint;
 import android.content.ComponentName;
@@ -26,7 +27,6 @@
 import androidx.annotation.Nullable;
 import androidx.annotation.VisibleForTesting;
 import com.google.android.gms.common.stats.ConnectionTracker;
-import com.google.android.gms.common.util.concurrent.NamedThreadFactory;
 import com.google.android.gms.tasks.Task;
 import com.google.android.gms.tasks.TaskCompletionSource;
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
@@ -35,7 +35,6 @@
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.ScheduledThreadPoolExecutor;
-import java.util.concurrent.TimeUnit;
 
 /**
  * Helper object to abstract the ServiceConnection lifecycle for binding to services within the same
@@ -65,7 +64,7 @@ void arrangeTimeout(ScheduledExecutorService executor) {
                 finish();
               },
               EnhancedIntentService.MESSAGE_TIMEOUT_S,
-              TimeUnit.SECONDS);
+              SECONDS);
 
       getTask()
           .addOnCompleteListener(
@@ -100,18 +99,20 @@ void finish() {
   @GuardedBy("this")
   private boolean connectionInProgress = false;
 
-  // TODO(b/258424124): Migrate to go/firebase-android-executors
-  @SuppressLint("ThreadPoolCreation")
   WithinAppServiceConnection(Context context, String action) {
     // Class instances are owned by a static variable in FirebaseInstanceIdReceiver
     // and GcmReceiver so that they survive getting gc'd and reinstantiated, so use a
     // scheduled thread pool executor with core size of 0 so that the no threads will be
     // kept idle.
-    this(
-        context,
-        action,
-        new ScheduledThreadPoolExecutor(
-            0, new NamedThreadFactory("Firebase-FirebaseInstanceIdServiceConnection")));
+    this(context, action, createScheduledThreadPoolExecutor());
+  }
+
+  @SuppressLint("ThreadPoolCreation")
+  private static ScheduledThreadPoolExecutor createScheduledThreadPoolExecutor() {
+    ScheduledThreadPoolExecutor threadPoolExecutor = new ScheduledThreadPoolExecutor(1);
+    threadPoolExecutor.setKeepAliveTime(EnhancedIntentService.MESSAGE_TIMEOUT_S * 2, SECONDS);
+    threadPoolExecutor.allowCoreThreadTimeOut(true);
+    return threadPoolExecutor;
   }
 
   @VisibleForTesting