Improve Real-time response Handling for Remote Config

firebase-config/CHANGELOG.md

@@ -1,5 +1,8 @@
 # Unreleased
-
+* [changed] This update introduces improvements to how the SDK handles real-time requests when a 
+  Firebase project has exceeded its available quota for real-time services. Released in anticipation
+  of future quota enforcement, this change is designed to fetch the latest template even when the 
+  quota is exhausted.
 
 # 22.1.2
 * [fixed] Fixed `NetworkOnMainThreadException` on Android versions below 8 by disconnecting 

firebase-config/src/main/java/com/google/firebase/remoteconfig/internal/ConfigAutoFetch.java

@@ -19,6 +19,8 @@
 import android.util.Log;
 import androidx.annotation.GuardedBy;
 import androidx.annotation.VisibleForTesting;
+import com.google.android.gms.common.util.Clock;
+import com.google.android.gms.common.util.DefaultClock;
 import com.google.android.gms.tasks.Task;
 import com.google.android.gms.tasks.Tasks;
 import com.google.firebase.remoteconfig.ConfigUpdate;
@@ -31,6 +33,7 @@
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.net.HttpURLConnection;
+import java.util.Date;
 import java.util.Random;
 import java.util.Set;
 import java.util.concurrent.ScheduledExecutorService;
@@ -43,6 +46,7 @@ public class ConfigAutoFetch {
   private static final int MAXIMUM_FETCH_ATTEMPTS = 3;
   private static final String TEMPLATE_VERSION_KEY = "latestTemplateVersionNumber";
   private static final String REALTIME_DISABLED_KEY = "featureDisabled";
+  private static final String REALTIME_RETRY_INTERVAL = "retryIntervalSeconds";
 
   @GuardedBy("this")
   private final Set<ConfigUpdateListener> eventListeners;
@@ -54,6 +58,8 @@ public class ConfigAutoFetch {
   private final ConfigUpdateListener retryCallback;
   private final ScheduledExecutorService scheduledExecutorService;
   private final Random random;
+  private final Clock clock;
+  private final ConfigSharedPrefsClient sharedPrefsClient;
   private boolean isInBackground;
 
   public ConfigAutoFetch(
@@ -62,7 +68,8 @@ public ConfigAutoFetch(
       ConfigCacheClient activatedCache,
       Set<ConfigUpdateListener> eventListeners,
       ConfigUpdateListener retryCallback,
-      ScheduledExecutorService scheduledExecutorService) {
+      ScheduledExecutorService scheduledExecutorService,
+      ConfigSharedPrefsClient sharedPrefsClient) {
     this.httpURLConnection = httpURLConnection;
     this.configFetchHandler = configFetchHandler;
     this.activatedCache = activatedCache;
@@ -71,6 +78,18 @@ public ConfigAutoFetch(
     this.scheduledExecutorService = scheduledExecutorService;
     this.random = new Random();
     this.isInBackground = false;
+    this.sharedPrefsClient = sharedPrefsClient;
+    clock = DefaultClock.getInstance();
+  }
+
+  // Increase the backoff duration with a new end time based on Retry Interval
+  private synchronized void updateBackoffMetadataWithRetryInterval(int realtimeRetryInterval) {
+    Date currentTime = new Date(clock.currentTimeMillis());
+    long backoffDurationInMillis = realtimeRetryInterval * 1000L;
+    Date backoffEndTime = new Date(currentTime.getTime() + backoffDurationInMillis);
+
+    // Persist the new values to disk-backed metadata.
+    sharedPrefsClient.setRealtimeBackoffEndTime(backoffEndTime);
   }
 
   private synchronized void propagateErrors(FirebaseRemoteConfigException exception) {
@@ -190,6 +209,15 @@ private void handleNotifications(InputStream inputStream) throws IOException {
               autoFetch(MAXIMUM_FETCH_ATTEMPTS, targetTemplateVersion);
             }
           }
+
+          // This field in the response indicates that the realtime request should retry after the
+          // specified interval to establish a long-lived connection. This interval extends the
+          // backoff duration without affecting the number of retries, so it will not enter an
+          // exponential backoff state.
+          if (jsonObject.has(REALTIME_RETRY_INTERVAL)) {
+            int realtimeRetryInterval = jsonObject.getInt(REALTIME_RETRY_INTERVAL);
+            updateBackoffMetadataWithRetryInterval(realtimeRetryInterval);
+          }
         } catch (JSONException ex) {
           // Message was mangled up and so it was unable to be parsed. User is notified of this
           // because it there could be a new configuration that needs to be fetched.

firebase-config/src/main/java/com/google/firebase/remoteconfig/internal/ConfigRealtimeHttpClient.java

@@ -469,7 +469,8 @@ public void onError(@NonNull FirebaseRemoteConfigException error) {
         activatedCache,
         listeners,
         retryCallback,
-        scheduledExecutorService);
+        scheduledExecutorService,
+        sharedPrefsClient);
   }
 
   // HTTP status code that the Realtime client should retry on.

firebase-config/src/main/java/com/google/firebase/remoteconfig/internal/ConfigSharedPrefsClient.java

@@ -394,6 +394,16 @@ void setRealtimeBackoffMetadata(int numFailedStreams, Date backoffEndTime) {
     }
   }
 
+  @VisibleForTesting
+  public void setRealtimeBackoffEndTime(Date backoffEndTime) {
+    synchronized (realtimeBackoffMetadataLock) {
+      frcSharedPrefs
+          .edit()
+          .putLong(REALTIME_BACKOFF_END_TIME_IN_MILLIS_KEY, backoffEndTime.getTime())
+          .apply();
+    }
+  }
+
   void resetRealtimeBackoff() {
     setRealtimeBackoffMetadata(NO_FAILED_REALTIME_STREAMS, NO_BACKOFF_TIME);
   }

firebase-config/src/test/java/com/google/firebase/remoteconfig/FirebaseRemoteConfigTest.java

@@ -351,7 +351,8 @@ public void onError(@NonNull FirebaseRemoteConfigException error) {
             mockActivatedCache,
             listeners,
             mockRetryListener,
-            scheduledExecutorService);
+            scheduledExecutorService,
+            sharedPrefsClient);
     configAutoFetch.setIsInBackground(false);
     realtimeSharedPrefsClient =
         new ConfigSharedPrefsClient(
@@ -1551,6 +1552,24 @@ public void realtimeStreamListen_andUnableToParseMessage() throws Exception {
     verify(mockInvalidMessageEventListener).onError(any(FirebaseRemoteConfigClientException.class));
   }
 
+  @Test
+  public void realtime_updatesBackoffMetadataWithProvidedRetryInterval() throws Exception {
+    ConfigRealtimeHttpClient configRealtimeHttpClientSpy = spy(configRealtimeHttpClient);
+    when(mockHttpURLConnection.getResponseCode()).thenReturn(200);
+    int expectedRetryInterval = 240;
+    when(mockHttpURLConnection.getInputStream())
+        .thenReturn(
+            new ByteArrayInputStream(
+                String.format(
+                        "{ \"latestTemplateVersionNumber\": 1, \"retryIntervalSeconds\": %d }",
+                        expectedRetryInterval)
+                    .getBytes(StandardCharsets.UTF_8)));
+    when(mockFetchHandler.getTemplateVersionNumber()).thenReturn(1L);
+    configAutoFetch.listenForNotifications();
+
+    verify(sharedPrefsClient, times(1)).setRealtimeBackoffEndTime(any());
+  }
+
   @Test
   public void realtime_stream_listen_get_inputstream_fail() throws Exception {
     InputStream inputStream = mock(InputStream.class);