xds: implement ignore_resource_deletion server feature

xds/src/main/java/io/grpc/xds/Bootstrapper.java

@@ -62,10 +62,21 @@ abstract static class ServerInfo {
 
     abstract boolean useProtocolV3();
 
+    abstract boolean ignoreResourceDeletion();
+
     @VisibleForTesting
     static ServerInfo create(
         String target, ChannelCredentials channelCredentials, boolean useProtocolV3) {
-      return new AutoValue_Bootstrapper_ServerInfo(target, channelCredentials, useProtocolV3);
+      return new AutoValue_Bootstrapper_ServerInfo(target, channelCredentials, useProtocolV3,
+          false);
+    }
+
+    @VisibleForTesting
+    static ServerInfo create(
+        String target, ChannelCredentials channelCredentials, boolean useProtocolV3,
+        boolean ignoreResourceDeletion) {
+      return new AutoValue_Bootstrapper_ServerInfo(target, channelCredentials, useProtocolV3,
+          ignoreResourceDeletion);
     }
   }
 

xds/src/main/java/io/grpc/xds/BootstrapperImpl.java

@@ -54,15 +54,22 @@ class BootstrapperImpl extends Bootstrapper {
   private static final String BOOTSTRAP_CONFIG_SYS_PROPERTY = "io.grpc.xds.bootstrapConfig";
   @VisibleForTesting
   static String bootstrapConfigFromSysProp = System.getProperty(BOOTSTRAP_CONFIG_SYS_PROPERTY);
-  private static final String XDS_V3_SERVER_FEATURE = "xds_v3";
+
+  // Feature-gating environment variables.
+  static boolean enableFederation =
+      !Strings.isNullOrEmpty(System.getenv("GRPC_EXPERIMENTAL_XDS_FEDERATION"))
+          && Boolean.parseBoolean(System.getenv("GRPC_EXPERIMENTAL_XDS_FEDERATION"));
+
+  // Client features.
   @VisibleForTesting
   static final String CLIENT_FEATURE_DISABLE_OVERPROVISIONING =
       "envoy.lb.does_not_support_overprovisioning";
   @VisibleForTesting
   static final String CLIENT_FEATURE_RESOURCE_IN_SOTW = "xds.config.resource-in-sotw";
-  static boolean enableFederation =
-      !Strings.isNullOrEmpty(System.getenv("GRPC_EXPERIMENTAL_XDS_FEDERATION"))
-          && Boolean.parseBoolean(System.getenv("GRPC_EXPERIMENTAL_XDS_FEDERATION"));
+
+  // Server features.
+  private static final String SERVER_FEATURE_XDS_V3 = "xds_v3";
+  private static final String SERVER_FEATURE_IGNORE_RESOURCE_DELETION = "ignore_resource_deletion";
 
   private final XdsLogger logger;
   private FileReader reader = LocalFileReader.INSTANCE;
@@ -275,12 +282,15 @@ private static List<ServerInfo> parseServerInfos(List<?> rawServerConfigs, XdsLo
       }
 
       boolean useProtocolV3 = false;
+      boolean ignoreResourceDeletion = false;
       List<String> serverFeatures = JsonUtil.getListOfStrings(serverConfig, "server_features");
       if (serverFeatures != null) {
         logger.log(XdsLogLevel.INFO, "Server features: {0}", serverFeatures);
-        useProtocolV3 = serverFeatures.contains(XDS_V3_SERVER_FEATURE);
+        useProtocolV3 = serverFeatures.contains(SERVER_FEATURE_XDS_V3);
+        ignoreResourceDeletion = serverFeatures.contains(SERVER_FEATURE_IGNORE_RESOURCE_DELETION);
       }
-      servers.add(ServerInfo.create(serverUri, channelCredentials, useProtocolV3));
+      servers.add(
+          ServerInfo.create(serverUri, channelCredentials, useProtocolV3, ignoreResourceDeletion));
     }
     return servers.build();
   }

xds/src/main/java/io/grpc/xds/ClientXdsClient.java

@@ -2156,8 +2156,7 @@ public void run() {
         ResourceSubscriber subscriber = ldsResourceSubscribers.get(resourceName);
         subscriber.removeWatcher(watcher);
         if (!subscriber.isWatched()) {
-          subscriber.stopTimer();
-          logger.log(XdsLogLevel.INFO, "Unsubscribe LDS resource {0}", resourceName);
+          subscriber.cancelResourceWatch();
           ldsResourceSubscribers.remove(resourceName);
           if (subscriber.xdsChannel != null) {
             subscriber.xdsChannel.adjustResourceSubscription(ResourceType.LDS);
@@ -2194,8 +2193,7 @@ public void run() {
         ResourceSubscriber subscriber = rdsResourceSubscribers.get(resourceName);
         subscriber.removeWatcher(watcher);
         if (!subscriber.isWatched()) {
-          subscriber.stopTimer();
-          logger.log(XdsLogLevel.INFO, "Unsubscribe RDS resource {0}", resourceName);
+          subscriber.cancelResourceWatch();
           rdsResourceSubscribers.remove(resourceName);
           if (subscriber.xdsChannel != null) {
             subscriber.xdsChannel.adjustResourceSubscription(ResourceType.RDS);
@@ -2232,8 +2230,7 @@ public void run() {
         ResourceSubscriber subscriber = cdsResourceSubscribers.get(resourceName);
         subscriber.removeWatcher(watcher);
         if (!subscriber.isWatched()) {
-          subscriber.stopTimer();
-          logger.log(XdsLogLevel.INFO, "Unsubscribe CDS resource {0}", resourceName);
+          subscriber.cancelResourceWatch();
           cdsResourceSubscribers.remove(resourceName);
           if (subscriber.xdsChannel != null) {
             subscriber.xdsChannel.adjustResourceSubscription(ResourceType.CDS);
@@ -2270,8 +2267,7 @@ public void run() {
         ResourceSubscriber subscriber = edsResourceSubscribers.get(resourceName);
         subscriber.removeWatcher(watcher);
         if (!subscriber.isWatched()) {
-          subscriber.stopTimer();
-          logger.log(XdsLogLevel.INFO, "Unsubscribe EDS resource {0}", resourceName);
+          subscriber.cancelResourceWatch();
           edsResourceSubscribers.remove(resourceName);
           if (subscriber.xdsChannel != null) {
             subscriber.xdsChannel.adjustResourceSubscription(ResourceType.EDS);
@@ -2320,7 +2316,7 @@ public void run() {
   Bootstrapper.BootstrapInfo getBootstrapInfo() {
     return bootstrapInfo;
   }
-  
+
   @Override
   public String toString() {
     return logId.toString();
@@ -2370,29 +2366,18 @@ private void handleResourceUpdate(
       } else if (type == ResourceType.LDS || type == ResourceType.CDS) {
         if (subscriber.data != null && invalidResources.contains(resourceName)) {
           // Update is rejected but keep using the cached data.
-          if (type == ResourceType.LDS) {
-            LdsUpdate ldsUpdate = (LdsUpdate) subscriber.data;
-            io.grpc.xds.HttpConnectionManager hcm = ldsUpdate.httpConnectionManager();
-            if (hcm != null) {
-              String rdsName = hcm.rdsName();
-              if (rdsName != null) {
-                retainedResources.add(rdsName);
-              }
-            }
-          } else {
-            CdsUpdate cdsUpdate = (CdsUpdate) subscriber.data;
-            String edsName = cdsUpdate.edsServiceName();
-            if (edsName == null) {
-              edsName = cdsUpdate.clusterName();
-            }
-            retainedResources.add(edsName);
-          }
+          retainDependentResource(subscriber, retainedResources);
         } else if (invalidResources.contains(resourceName)) {
           subscriber.onError(Status.UNAVAILABLE.withDescription(errorDetail));
         } else {
           // For State of the World services, notify watchers when their watched resource is missing
           // from the ADS update.
           subscriber.onAbsent();
+          // Retain any dependent resources if the resource deletion is ignored
+          // per bootstrap ignore_resource_deletion server feature.
+          if (!subscriber.absent) {
+            retainDependentResource(subscriber, retainedResources);
+          }
         }
       }
     }
@@ -2409,6 +2394,28 @@ private void handleResourceUpdate(
     }
   }
 
+  private void retainDependentResource(
+      ResourceSubscriber subscriber, Set<String> retainedResources) {
+    if (subscriber.data == null) {
+      return;
+    }
+    String resourceName = null;
+    if (subscriber.type == ResourceType.LDS) {
+      LdsUpdate ldsUpdate = (LdsUpdate) subscriber.data;
+      io.grpc.xds.HttpConnectionManager hcm = ldsUpdate.httpConnectionManager();
+      if (hcm != null) {
+        resourceName = hcm.rdsName();
+      }
+    } else if (subscriber.type == ResourceType.CDS) {
+      CdsUpdate cdsUpdate = (CdsUpdate) subscriber.data;
+      resourceName = cdsUpdate.edsServiceName();
+    }
+
+    if (resourceName != null) {
+      retainedResources.add(resourceName);
+    }
+  }
+
   private static final class ParsedResource {
     private final ResourceUpdate resourceUpdate;
     private final Any rawResource;
@@ -2431,15 +2438,18 @@ private Any getRawResource() {
    * Tracks a single subscribed resource.
    */
   private final class ResourceSubscriber {
-    private final ServerInfo serverInfo;
+    @Nullable private final ServerInfo serverInfo;
     @Nullable private final AbstractXdsClient xdsChannel;
     private final ResourceType type;
     private final String resource;
     private final Set<ResourceWatcher> watchers = new HashSet<>();
-    private ResourceUpdate data;
+    @Nullable private ResourceUpdate data;
     private boolean absent;
-    private ScheduledHandle respTimer;
-    private ResourceMetadata metadata;
+    // Tracks whether the deletion has been ignored per bootstrap server feature.
+    // See https://github.com/grpc/proposal/blob/master/A53-xds-ignore-resource-deletion.md
+    private boolean resourceDeletionIgnored;
+    @Nullable private ScheduledHandle respTimer;
+    @Nullable private ResourceMetadata metadata;
     @Nullable private String errorDescription;
 
     ResourceSubscriber(ResourceType type, String resource) {
@@ -2533,6 +2543,21 @@ void stopTimer() {
       }
     }
 
+    void cancelResourceWatch() {
+      if (isWatched()) {
+        throw new IllegalStateException("Can't cancel resource watch with active watchers present");
+      }
+      stopTimer();
+      String message = "Unsubscribing {0} resource {1} from server {2}";
+      XdsLogLevel logLevel = XdsLogLevel.INFO;
+      if (resourceDeletionIgnored) {
+        message += " for which we previously ignored a deletion";
+        logLevel = XdsLogLevel.FORCE_INFO;
+      }
+      logger.log(logLevel, message, type, resource,
+          serverInfo != null ? serverInfo.target() : "unknown");
+    }
+
     boolean isWatched() {
       return !watchers.isEmpty();
     }
@@ -2547,6 +2572,12 @@ void onData(ParsedResource parsedResource, String version, long updateTime) {
       ResourceUpdate oldData = this.data;
       this.data = parsedResource.getResourceUpdate();
       absent = false;
+      if (resourceDeletionIgnored) {
+        logger.log(XdsLogLevel.FORCE_INFO, "xds server {0}: server returned new version "
+                + "of resource for which we previously ignored a deletion: type {1} name {2}",
+            serverInfo != null ? serverInfo.target() : "unknown", type, resource);
+        resourceDeletionIgnored = false;
+      }
       if (!Objects.equals(oldData, data)) {
         for (ResourceWatcher watcher : watchers) {
           notifyWatcher(watcher, data);
@@ -2558,6 +2589,22 @@ void onAbsent() {
       if (respTimer != null && respTimer.isPending()) {  // too early to conclude absence
         return;
       }
+
+      // Ignore deletion of State of the World resources when this feature is on,
+      // and the resource is reusable.
+      boolean ignoreResourceDeletionEnabled =
+          serverInfo != null && serverInfo.ignoreResourceDeletion();
+      boolean isStateOfTheWorld = (type == ResourceType.LDS || type == ResourceType.CDS);
+      if (ignoreResourceDeletionEnabled && isStateOfTheWorld && data != null) {
+        if (!resourceDeletionIgnored) {
+          logger.log(XdsLogLevel.FORCE_WARNING,
+              "xds server {0}: ignoring deletion for resource type {1} name {2}}",
+              serverInfo.target(), type, resource);
+          resourceDeletionIgnored = true;
+        }
+        return;
+      }
+
       logger.log(XdsLogLevel.INFO, "Conclude {0} resource {1} not exist", type, resource);
       if (!absent) {
         data = null;

xds/src/main/java/io/grpc/xds/XdsLogger.java

@@ -81,6 +81,10 @@ private static Level toJavaLogLevel(XdsLogLevel level) {
         return Level.FINE;
       case INFO:
         return Level.FINER;
+      case FORCE_INFO:
+        return Level.INFO;
+      case FORCE_WARNING:
+        return Level.WARNING;
       default:
         return Level.FINEST;
     }
@@ -89,6 +93,11 @@ private static Level toJavaLogLevel(XdsLogLevel level) {
   /**
    * Log levels. See the table below for the mapping from the XdsLogger levels to
    * Java logger levels.
+   *
+   * <p><b>NOTE:</b>
+   *   Please use {@code FORCE_} levels with care, only when the message is expected to be
+   *   surfaced to the library user. Normally libraries should minimize the usage
+   *   of highly visible logs.
    * <pre>
    * +---------------------+-------------------+
    * | XdsLogger Level     | Java Logger Level |
@@ -97,13 +106,17 @@ private static Level toJavaLogLevel(XdsLogLevel level) {
    * | INFO                | FINER             |
    * | WARNING             | FINE              |
    * | ERROR               | FINE              |
+   * | FORCE_INFO          | INFO              |
+   * | FORCE_WARNING       | WARNING           |
    * +---------------------+-------------------+
    * </pre>
    */
   enum XdsLogLevel {
     DEBUG,
     INFO,
     WARNING,
-    ERROR
+    ERROR,
+    FORCE_INFO,
+    FORCE_WARNING,
   }
 }

xds/src/test/java/io/grpc/xds/BootstrapperImplTest.java

@@ -578,6 +578,8 @@ public void useV2ProtocolByDefault() throws XdsInitializationException {
     ServerInfo serverInfo = Iterables.getOnlyElement(info.servers());
     assertThat(serverInfo.target()).isEqualTo(SERVER_URI);
     assertThat(serverInfo.channelCredentials()).isInstanceOf(InsecureChannelCredentials.class);
+    assertThat(serverInfo.ignoreResourceDeletion()).isFalse();
+    // xds v2: xds v3 disabled
     assertThat(serverInfo.useProtocolV3()).isFalse();
   }
 
@@ -600,9 +602,59 @@ public void useV3ProtocolIfV3FeaturePresent() throws XdsInitializationException
     ServerInfo serverInfo = Iterables.getOnlyElement(info.servers());
     assertThat(serverInfo.target()).isEqualTo(SERVER_URI);
     assertThat(serverInfo.channelCredentials()).isInstanceOf(InsecureChannelCredentials.class);
+    assertThat(serverInfo.ignoreResourceDeletion()).isFalse();
+    // xds_v3 enabled
     assertThat(serverInfo.useProtocolV3()).isTrue();
   }
 
+  @Test
+  public void serverFeatureIgnoreResourceDeletion() throws XdsInitializationException {
+    String rawData = "{\n"
+        + "  \"xds_servers\": [\n"
+        + "    {\n"
+        + "      \"server_uri\": \"" + SERVER_URI + "\",\n"
+        + "      \"channel_creds\": [\n"
+        + "        {\"type\": \"insecure\"}\n"
+        + "      ],\n"
+        + "      \"server_features\": [\"ignore_resource_deletion\"]\n"
+        + "    }\n"
+        + "  ]\n"
+        + "}";
+
+    bootstrapper.setFileReader(createFileReader(BOOTSTRAP_FILE_PATH, rawData));
+    BootstrapInfo info = bootstrapper.bootstrap();
+    ServerInfo serverInfo = Iterables.getOnlyElement(info.servers());
+    assertThat(serverInfo.target()).isEqualTo(SERVER_URI);
+    assertThat(serverInfo.channelCredentials()).isInstanceOf(InsecureChannelCredentials.class);
+    // Only ignore_resource_deletion feature enabled: confirm it's on, and xds_v3 is off.
+    assertThat(serverInfo.useProtocolV3()).isFalse();
+    assertThat(serverInfo.ignoreResourceDeletion()).isTrue();
+  }
+
+  @Test
+  public void serverFeatureIgnoreResourceDeletion_xdsV3() throws XdsInitializationException {
+    String rawData = "{\n"
+        + "  \"xds_servers\": [\n"
+        + "    {\n"
+        + "      \"server_uri\": \"" + SERVER_URI + "\",\n"
+        + "      \"channel_creds\": [\n"
+        + "        {\"type\": \"insecure\"}\n"
+        + "      ],\n"
+        + "      \"server_features\": [\"xds_v3\", \"ignore_resource_deletion\"]\n"
+        + "    }\n"
+        + "  ]\n"
+        + "}";
+
+    bootstrapper.setFileReader(createFileReader(BOOTSTRAP_FILE_PATH, rawData));
+    BootstrapInfo info = bootstrapper.bootstrap();
+    ServerInfo serverInfo = Iterables.getOnlyElement(info.servers());
+    assertThat(serverInfo.target()).isEqualTo(SERVER_URI);
+    assertThat(serverInfo.channelCredentials()).isInstanceOf(InsecureChannelCredentials.class);
+    // xds_v3 and ignore_resource_deletion features enabled: confirm both are on.
+    assertThat(serverInfo.useProtocolV3()).isTrue();
+    assertThat(serverInfo.ignoreResourceDeletion()).isTrue();
+  }
+
   @Test
   public void notFound() {
     BootstrapperImpl.bootstrapPathFromEnvVar = null;