From 154e40d84aa4590800f70842ab60cb5f8e8dbf2a Mon Sep 17 00:00:00 2001
From: PapaCharlie <paul.chesnais@gmail.com>
Date: Thu, 4 Jan 2024 18:35:52 -0500
Subject: [PATCH] Respect xDS deletions

---
 .../java/com/linkedin/d2/xds/XdsClient.java   |  6 +++
 .../com/linkedin/d2/xds/XdsClientImpl.java    | 11 ++++-
 .../d2/xds/XdsToD2PropertiesAdaptor.java      | 46 +++++++++++++++++--
 3 files changed, 56 insertions(+), 7 deletions(-)

diff --git a/d2/src/main/java/com/linkedin/d2/xds/XdsClient.java b/d2/src/main/java/com/linkedin/d2/xds/XdsClient.java
index 5c1d1e2c28..32a160cd3c 100644
--- a/d2/src/main/java/com/linkedin/d2/xds/XdsClient.java
+++ b/d2/src/main/java/com/linkedin/d2/xds/XdsClient.java
@@ -43,16 +43,22 @@ interface ResourceWatcher
   interface NodeResourceWatcher extends ResourceWatcher
   {
     void onChanged(NodeUpdate update);
+
+    void onDelete(String resourceName);
   }
 
   interface SymlinkNodeResourceWatcher extends ResourceWatcher
   {
     void onChanged(String resourceName, NodeUpdate update);
+
+    void onDelete(String resourceName);
   }
 
   interface D2URIMapResourceWatcher extends ResourceWatcher
   {
     void onChanged(D2URIMapUpdate update);
+
+    void onDelete(String resourceName);
   }
 
   interface ResourceUpdate
diff --git a/d2/src/main/java/com/linkedin/d2/xds/XdsClientImpl.java b/d2/src/main/java/com/linkedin/d2/xds/XdsClientImpl.java
index 59765a311e..25fe996be9 100644
--- a/d2/src/main/java/com/linkedin/d2/xds/XdsClientImpl.java
+++ b/d2/src/main/java/com/linkedin/d2/xds/XdsClientImpl.java
@@ -443,19 +443,21 @@ private static final class DiscoveryResponseData
   {
     private final ResourceType _resourceType;
     private final List<Resource> _resources;
+    private final List<String> _removedResources;
     private final String _nonce;
 
-    DiscoveryResponseData(ResourceType resourceType, List<Resource> resources, String nonce)
+    DiscoveryResponseData(ResourceType resourceType, List<Resource> resources, List<String> removedResources, String nonce)
     {
       _resourceType = resourceType;
       _resources = resources;
+      _removedResources = removedResources;
       _nonce = nonce;
     }
 
     static DiscoveryResponseData fromEnvoyProto(DeltaDiscoveryResponse proto)
     {
       return new DiscoveryResponseData(ResourceType.fromTypeUrl(proto.getTypeUrl()), proto.getResourcesList(),
-          proto.getNonce());
+          proto.getRemovedResourcesList(), proto.getNonce());
     }
 
     ResourceType getResourceType()
@@ -468,6 +470,11 @@ List<Resource> getResourcesList()
       return _resources;
     }
 
+    List<String> getRemovedResources()
+    {
+      return _removedResources;
+    }
+
     String getNonce()
     {
       return _nonce;
diff --git a/d2/src/main/java/com/linkedin/d2/xds/XdsToD2PropertiesAdaptor.java b/d2/src/main/java/com/linkedin/d2/xds/XdsToD2PropertiesAdaptor.java
index ccf87b4078..dd57acc013 100644
--- a/d2/src/main/java/com/linkedin/d2/xds/XdsToD2PropertiesAdaptor.java
+++ b/d2/src/main/java/com/linkedin/d2/xds/XdsToD2PropertiesAdaptor.java
@@ -43,7 +43,6 @@
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
-import org.apache.commons.lang3.StringUtils;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -225,6 +224,12 @@ public void onChanged(XdsClient.NodeUpdate update)
         }
       }
 
+      @Override
+      public void onDelete(String name)
+      {
+        _serviceEventBus.publishRemove(name);
+      }
+
       @Override
       public void onError(Status error)
       {
@@ -286,6 +291,12 @@ private void publishClusterData(String clusterName, ClusterProperties properties
         }
       }
 
+      @Override
+      public void onDelete(String name)
+      {
+        _clusterEventBus.publishRemove(name);
+      }
+
       @Override
       public void onError(Status error)
       {
@@ -325,6 +336,13 @@ public void onChanged(String resourceName, XdsClient.NodeUpdate update)
         listenToUris(actualNodeName);
       }
 
+      @Override
+      public void onDelete(String resourceName)
+      {
+        // TODO: Is this all we need to do here?
+        removeSymlink(symlinkName);
+      }
+
       @Override
       public void onError(Status error)
       {
@@ -339,14 +357,26 @@ public void onReconnect()
     };
   }
 
-  private void updateSymlinkAndActualNodeMap(String symlinkName, String actualNodeName) {
-    synchronized (_symlinkAndActualNodeLock) {
+  private void updateSymlinkAndActualNodeMap(String symlinkName, String actualNodeName)
+  {
+    synchronized (_symlinkAndActualNodeLock)
+    {
       _symlinkAndActualNode.put(symlinkName, actualNodeName);
     }
   }
 
-  private String getSymlink(String actualNodeName) {
-    synchronized (_symlinkAndActualNodeLock) {
+  private String removeSymlink(String symlinkName)
+  {
+    synchronized (_symlinkAndActualNodeLock)
+    {
+      return _symlinkAndActualNode.remove(symlinkName);
+    }
+  }
+
+  private String getSymlink(String actualNodeName)
+  {
+    synchronized (_symlinkAndActualNodeLock)
+    {
       return _symlinkAndActualNode.inverse().get(actualNodeName);
     }
   }
@@ -486,6 +516,12 @@ private void mergeAndPublishUris(String clusterName)
       }
     }
 
+    @Override
+    public void onDelete(String resourceName)
+    {
+      _uriEventBus.publishRemove(resourceName);
+    }
+
     @Override
     public void onError(Status error)
     {