Fixed part of the dynamic configuration of ConfigurationDiscoveryService that does not take effect under certain circumstances. (#6975)

CHANGES.md

@@ -28,6 +28,7 @@ Release Notes.
 * Fix NPE when thrift field is nested in plugin `thrift`
 * Fix possible NullPointerException in agent's ES plugin.
 * Fix the conversion problem of float type in ConfigInitializer.
+* Fixed part of the dynamic configuration of ConfigurationDiscoveryService that does not take effect under certain circumstances.
 
 #### OAP-Backend
 * BugFix: filter invalid Envoy access logs whose socket address is empty.

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

@@ -62,6 +62,8 @@ public class ConfigurationDiscoveryService implements BootService, GRPCChannelLi
     private String uuid;
     private final Register register = new Register();
 
+    private volatile int lastRegisterWatcherSize;
+
     private volatile ScheduledFuture<?> getDynamicConfigurationFuture;
     private volatile GRPCChannelStatus status = GRPCChannelStatus.DISCONNECT;
     private volatile ConfigurationDiscoveryServiceGrpc.ConfigurationDiscoveryServiceBlockingStub configurationDiscoveryServiceBlockingStub;
@@ -206,6 +208,15 @@ public class ConfigurationDiscoveryService implements BootService, GRPCChannelLi
             try {
                 ConfigurationSyncRequest.Builder builder = ConfigurationSyncRequest.newBuilder();
                 builder.setService(Config.Agent.SERVICE_NAME);
+
+                // Some plugin will register watcher later.
+                final int size = register.keys().size();
+                if (lastRegisterWatcherSize != size) {
+                    // reset uuid, avoid the same uuid causing the configuration not to be updated.
+                    uuid = null;
+                    lastRegisterWatcherSize = size;
+                }
+
                 if (null != uuid) {
                     builder.setUuid(uuid);
                 }