Implement ignore_resource_deletion resource handling logic

Author: sergiitk

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 +2366,17 @@ 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 server setting.
+          if (!subscriber.absent) {
+            retainDependentResource(subscriber, retainedResources);
+          }
         }
       }
     }
@@ -2409,6 +2393,28 @@ 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 +2437,18 @@ 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 server request.
+    // 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 +2542,19 @@ 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}";
+      if (resourceDeletionIgnored) {
+        message += " for which we previously ignored a deletion";
+      }
+      logger.log(XdsLogLevel.INFO, message, type, resource,
+          serverInfo != null ? serverInfo.target() : "unknown");
+    }
+
     boolean isWatched() {
       return !watchers.isEmpty();
     }
@@ -2547,6 +2569,12 @@ void onData(ParsedResource parsedResource, String version, long updateTime) {
       ResourceUpdate oldData = this.data;
       this.data = parsedResource.getResourceUpdate();
       absent = false;
+      if (resourceDeletionIgnored) {
+        logger.log(XdsLogLevel.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 +2586,18 @@ void onAbsent() {
       if (respTimer != null && respTimer.isPending()) {  // too early to conclude absence
         return;
       }
+
+      // Ignore deletion when the server instructs to, and the resource is reusable.
+      if (data != null && serverInfo != null && serverInfo.ignoreResourceDeletion()) {
+        if (!resourceDeletionIgnored) {
+          logger.log(XdsLogLevel.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;