Fix that the dynamic configuration is deleted on the server side but does not...

Fix that the dynamic configuration is deleted on the server side but does not take effect on the agent. (#6255)
Co-authored-by: 吴晟 Wu Sheng <wu.sheng@foxmail.com>

apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/conf/dynamic/ConfigurationDiscoveryService.java

@@ -18,15 +18,18 @@
 
 package org.apache.skywalking.apm.agent.core.conf.dynamic;
 
+import com.google.common.collect.Lists;
 import io.grpc.Channel;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Set;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
 import java.util.stream.Collectors;
 import lombok.Getter;
 import org.apache.skywalking.apm.agent.core.boot.BootService;
@@ -128,12 +131,13 @@ public class ConfigurationDiscoveryService implements BootService, GRPCChannelLi
      */
     public void handleConfigurationDiscoveryCommand(ConfigurationDiscoveryCommand configurationDiscoveryCommand) {
         final String responseUuid = configurationDiscoveryCommand.getUuid();
-        final List<KeyStringValuePair> config = configurationDiscoveryCommand.getConfig();
 
         if (responseUuid != null && Objects.equals(this.uuid, responseUuid)) {
             return;
         }
 
+        List<KeyStringValuePair> config = readConfig(configurationDiscoveryCommand);
+
         config.forEach(property -> {
             String propertyKey = property.getKey();
             WatcherHolder holder = register.get(propertyKey);
@@ -168,6 +172,30 @@ public class ConfigurationDiscoveryService implements BootService, GRPCChannelLi
         LOGGER.trace("Current configurations after the sync, configurations:{}", register.toString());
     }
 
+    /**
+     * Read the registered dynamic configuration, compare it with the dynamic configuration information returned by the
+     * service, and complete the dynamic configuration that has been deleted on the OAP.
+     *
+     * @param configurationDiscoveryCommand Describe dynamic configuration information
+     * @return Adapted dynamic configuration information
+     */
+    private List<KeyStringValuePair> readConfig(ConfigurationDiscoveryCommand configurationDiscoveryCommand) {
+        Map<String, KeyStringValuePair> commandConfigs = configurationDiscoveryCommand.getConfig()
+                                                                                      .stream()
+                                                                                      .collect(Collectors.toMap(
+                                                                                          KeyStringValuePair::getKey,
+                                                                                          Function.identity()
+                                                                                      ));
+        List<KeyStringValuePair> configList = Lists.newArrayList();
+        for (final String name : register.keys()) {
+            KeyStringValuePair command = commandConfigs.getOrDefault(name, KeyStringValuePair.newBuilder()
+                                                                                             .setKey(name)
+                                                                                             .build());
+            configList.add(command);
+        }
+        return configList;
+    }
+
     /**
      * get agent dynamic config through gRPC.
      */
@@ -213,6 +241,10 @@ public class ConfigurationDiscoveryService implements BootService, GRPCChannelLi
             return register.get(name);
         }
 
+        public Set<String> keys() {
+            return register.keySet();
+        }
+
         @Override
         public String toString() {
             ArrayList<String> registerTableDescription = new ArrayList<>(register.size());

oap-server/server-receiver-plugin/configuration-discovery-receiver-plugin/src/main/java/org/apache/skywalking/oap/server/recevier/configuration/discovery/AgentConfigurationsWatcher.java

@@ -18,22 +18,29 @@
 
 package org.apache.skywalking.oap.server.recevier.configuration.discovery;
 
-import java.io.StringReader;
+import org.apache.commons.codec.digest.DigestUtils;
 import org.apache.skywalking.oap.server.configuration.api.ConfigChangeWatcher;
 import org.apache.skywalking.oap.server.core.Const;
 import org.apache.skywalking.oap.server.library.module.ModuleProvider;
 
+import java.io.StringReader;
+import java.util.HashMap;
+
 /**
  * AgentConfigurationsWatcher used to handle dynamic configuration changes.
  */
 public class AgentConfigurationsWatcher extends ConfigChangeWatcher {
     private volatile String settingsString;
     private volatile AgentConfigurationsTable agentConfigurationsTable;
+    private final AgentConfigurations emptyAgentConfigurations;
 
     public AgentConfigurationsWatcher(ModuleProvider provider) {
         super(ConfigurationDiscoveryModule.NAME, provider, "agentConfigurations");
         this.settingsString = Const.EMPTY_STRING;
         this.agentConfigurationsTable = new AgentConfigurationsTable();
+        this.emptyAgentConfigurations = new AgentConfigurations(
+            null, new HashMap<>(), DigestUtils.sha512Hex("EMPTY")
+        );
     }
 
     @Override
@@ -54,7 +61,20 @@ public class AgentConfigurationsWatcher extends ConfigChangeWatcher {
         return settingsString;
     }
 
+    /**
+     * Get service dynamic configuration information, if there is no dynamic configuration information, return to empty
+     * dynamic configuration to prevent the server from deleted the dynamic configuration, but it does not take effect
+     * on the agent side.
+     *
+     * @param service Service name to be queried
+     * @return Service dynamic configuration information
+     */
     public AgentConfigurations getAgentConfigurations(String service) {
-        return agentConfigurationsTable.getAgentConfigurationsCache().get(service);
+        AgentConfigurations agentConfigurations = agentConfigurationsTable.getAgentConfigurationsCache().get(service);
+        if (null == agentConfigurations) {
+            return emptyAgentConfigurations;
+        } else {
+            return agentConfigurations;
+        }
     }
 }