diff --git a/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/boot/ServiceManager.java b/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/boot/ServiceManager.java
index e1ca40ab0..33d189958 100644
--- a/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/boot/ServiceManager.java
+++ b/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/boot/ServiceManager.java
@@ -19,8 +19,9 @@
 
 package org.apache.skywalking.apm.agent.core.boot;
 
-import java.util.HashMap;
+import java.util.Collections;
 import java.util.Iterator;
+import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.ServiceLoader;
 import org.apache.skywalking.apm.agent.core.logging.api.LogManager;
@@ -36,7 +37,7 @@ public enum ServiceManager {
     INSTANCE;
 
     private static final ILog logger = LogManager.getLogger(ServiceManager.class);
-    private Map<Class, BootService> bootedServices = new HashMap<Class, BootService>();
+    private Map<Class, BootService> bootedServices = Collections.emptyMap();
 
     public void boot() {
         bootedServices = loadAllServices();
@@ -57,7 +58,7 @@ public enum ServiceManager {
     }
 
     private Map<Class, BootService> loadAllServices() {
-        HashMap<Class, BootService> bootedServices = new HashMap<Class, BootService>();
+        Map<Class, BootService> bootedServices = new LinkedHashMap<Class, BootService>();
         Iterator<BootService> serviceIterator = load().iterator();
         while (serviceIterator.hasNext()) {
             BootService bootService = serviceIterator.next();
diff --git a/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/remote/CollectorDiscoveryService.java b/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/remote/CollectorDiscoveryService.java
index f7910f71d..b5d4f442e 100644
--- a/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/remote/CollectorDiscoveryService.java
+++ b/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/remote/CollectorDiscoveryService.java
@@ -44,13 +44,15 @@ public class CollectorDiscoveryService implements BootService {
 
     @Override
     public void boot() throws Throwable {
+        DiscoveryRestServiceClient discoveryRestServiceClient = new DiscoveryRestServiceClient();
+        discoveryRestServiceClient.run();
         future = Executors.newSingleThreadScheduledExecutor(new DefaultNamedThreadFactory("CollectorDiscoveryService"))
-            .scheduleAtFixedRate(new RunnableWithExceptionProtection(new DiscoveryRestServiceClient(),
+            .scheduleAtFixedRate(new RunnableWithExceptionProtection(discoveryRestServiceClient,
                     new RunnableWithExceptionProtection.CallbackWhenException() {
                         @Override public void handle(Throwable t) {
                             logger.error("unexpected exception.", t);
                         }
-                    }), 0,
+                    }), Config.Collector.DISCOVERY_CHECK_INTERVAL,
                 Config.Collector.DISCOVERY_CHECK_INTERVAL, TimeUnit.SECONDS);
     }