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 +58,7 @@ public class ConfigAutoFetch {
   private final ConfigUpdateListener retryCallback;
   private final ScheduledExecutorService scheduledExecutorService;
   private final Random random;
+  private final Clock clock;
   private boolean isInBackground;
 
   public ConfigAutoFetch(
@@ -71,6 +76,18 @@ public ConfigAutoFetch(
     this.scheduledExecutorService = scheduledExecutorService;
     this.random = new Random();
     this.isInBackground = false;
+    clock = DefaultClock.getInstance();
+  }
+
+  // Increase the backoff duration with a new end time based on Retry Interval
+  private synchronized void updateBackoffMetadataWithRetryInterval(
+      int realtimeRetryInterval, ConfigSharedPrefsClient sharedPrefsClient) {
+    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) {
@@ -106,7 +123,7 @@ private String parseAndValidateConfigUpdateMessage(String message) {
 
   // Check connection and establish InputStream
   @VisibleForTesting
-  public void listenForNotifications() {
+  public void listenForNotifications(ConfigSharedPrefsClient sharedPrefsClient) {
     if (httpURLConnection == null) {
       return;
     }
@@ -116,7 +133,7 @@ public void listenForNotifications() {
     InputStream inputStream = null;
     try {
       inputStream = httpURLConnection.getInputStream();
-      handleNotifications(inputStream);
+      handleNotifications(inputStream, sharedPrefsClient);
     } catch (IOException ex) {
       // If the real-time connection is at an unexpected lifecycle state when the app is
       // backgrounded, it's expected closing the httpURLConnection will throw an exception.
@@ -138,7 +155,8 @@ public void listenForNotifications() {
   }
 
   // Auto-fetch new config and execute callbacks on each new message
-  private void handleNotifications(InputStream inputStream) throws IOException {
+  private void handleNotifications(
+      InputStream inputStream, ConfigSharedPrefsClient sharedPrefsClient) throws IOException {
     BufferedReader reader = new BufferedReader((new InputStreamReader(inputStream, "utf-8")));
     String partialConfigUpdateMessage;
     String currentConfigUpdateMessage = "";
@@ -190,6 +208,11 @@ private void handleNotifications(InputStream inputStream) throws IOException {
               autoFetch(MAXIMUM_FETCH_ATTEMPTS, targetTemplateVersion);
             }
           }
+
+          if (jsonObject.has(REALTIME_RETRY_INTERVAL)) {
+            int realtimeRetryInterval = jsonObject.getInt(REALTIME_RETRY_INTERVAL);
+            updateBackoffMetadataWithRetryInterval(realtimeRetryInterval, sharedPrefsClient);
+          }
         } 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

@@ -554,7 +554,7 @@ public void beginRealtimeHttpStream() {
 
                   // Start listening for realtime notifications.
                   configAutoFetch = startAutoFetch(httpURLConnection);
-                  configAutoFetch.listenForNotifications();
+                  configAutoFetch.listenForNotifications(sharedPrefsClient);
                 }
               } catch (IOException e) {
                 if (isInBackground) {

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

@@ -1286,7 +1286,7 @@ public void realtime_stream_listen_and_end_connection() throws Exception {
     when(mockFetchHandler.fetchNowWithTypeAndAttemptNumber(
             ConfigFetchHandler.FetchType.REALTIME, 1))
         .thenReturn(Tasks.forResult(realtimeFetchedContainerResponse));
-    configAutoFetch.listenForNotifications();
+    configAutoFetch.listenForNotifications(sharedPrefsClient);
 
     verify(inputStreamSpy, times(2)).close();
   }
@@ -1299,7 +1299,7 @@ public void realtime_fetchesWithoutChangedParams_doesNotCallOnUpdate() throws Ex
                 "{ \"latestTemplateVersionNumber\": 1 }".getBytes(StandardCharsets.UTF_8)));
     when(mockFetchHandler.getTemplateVersionNumber()).thenReturn(1L);
     when(mockFetchHandler.fetch(0)).thenReturn(Tasks.forResult(firstFetchedContainerResponse));
-    configAutoFetch.listenForNotifications();
+    configAutoFetch.listenForNotifications(sharedPrefsClient);
 
     verifyNoInteractions(mockOnUpdateListener);
   }
@@ -1339,7 +1339,7 @@ public void realtime_okStatusCode_startAutofetchAndRetries() throws Exception {
     configRealtimeHttpClientSpy.beginRealtimeHttpStream();
     flushScheduledTasks();
 
-    verify(mockConfigAutoFetch).listenForNotifications();
+    verify(mockConfigAutoFetch).listenForNotifications(any());
     verify(configRealtimeHttpClientSpy).retryHttpConnectionWhenBackoffEnds();
   }
 
@@ -1490,7 +1490,7 @@ public void realtime_stream_listen_and_failsafe_enabled() throws Exception {
             new ByteArrayInputStream(
                 "{ \"featureDisabled\": true }".getBytes(StandardCharsets.UTF_8)));
     when(mockFetchHandler.getTemplateVersionNumber()).thenReturn(1L);
-    configAutoFetch.listenForNotifications();
+    configAutoFetch.listenForNotifications(sharedPrefsClient);
 
     verify(mockRetryListener).onError(any(FirebaseRemoteConfigServerException.class));
     verify(mockFetchHandler, never()).fetch(0);
@@ -1508,7 +1508,7 @@ public void realtime_stream_listen_and_failsafe_disabled() throws Exception {
     when(mockFetchHandler.fetchNowWithTypeAndAttemptNumber(
             ConfigFetchHandler.FetchType.REALTIME, 1))
         .thenReturn(Tasks.forResult(realtimeFetchedContainerResponse));
-    configAutoFetch.listenForNotifications();
+    configAutoFetch.listenForNotifications(sharedPrefsClient);
 
     verify(mockUnavailableEventListener, never())
         .onError(any(FirebaseRemoteConfigServerException.class));
@@ -1546,11 +1546,29 @@ public void realtimeStreamListen_andUnableToParseMessage() throws Exception {
     when(mockFetchHandler.fetchNowWithTypeAndAttemptNumber(
             ConfigFetchHandler.FetchType.REALTIME, 1))
         .thenReturn(Tasks.forResult(realtimeFetchedContainerResponse));
-    configAutoFetch.listenForNotifications();
+    configAutoFetch.listenForNotifications(sharedPrefsClient);
 
     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(sharedPrefsClient);
+
+    verify(sharedPrefsClient, times(1)).setRealtimeBackoffEndTime(any());
+  }
+
   @Test
   public void realtime_stream_listen_get_inputstream_fail() throws Exception {
     InputStream inputStream = mock(InputStream.class);
@@ -1561,7 +1579,7 @@ public void realtime_stream_listen_get_inputstream_fail() throws Exception {
     when(mockFetchHandler.fetchNowWithTypeAndAttemptNumber(
             ConfigFetchHandler.FetchType.REALTIME, 1))
         .thenReturn(Tasks.forResult(realtimeFetchedContainerResponse));
-    configAutoFetch.listenForNotifications();
+    configAutoFetch.listenForNotifications(sharedPrefsClient);
 
     verify(inputStream).close();
   }
@@ -1571,7 +1589,7 @@ public void realtime_stream_listen_get_inputstream_exception_handling() throws E
     InputStream inputStream = mock(InputStream.class);
     when(mockHttpURLConnection.getResponseCode()).thenReturn(200);
     when(mockHttpURLConnection.getInputStream()).thenThrow(IOException.class);
-    configAutoFetch.listenForNotifications();
+    configAutoFetch.listenForNotifications(sharedPrefsClient);
 
     verify(mockHttpURLConnection, times(1)).getInputStream();
     verify(inputStream, never()).close();