Adjust startup sequence.

apm-collector/apm-collector-core/src/main/java/org/skywalking/apm/collector/core/module/BootstrapFlow.java

@@ -58,9 +58,9 @@ public class BootstrapFlow {
                 }
             }
             logger.info("start the provider {} in {} module.", provider.name(), provider.getModuleName());
-            provider.start(configuration.getModuleConfiguration(provider.getModuleName()).getProviderConfiguration(provider.name()));
-
             provider.requiredCheck(provider.getModule().services());
+
+            provider.start(configuration.getModuleConfiguration(provider.getModuleName()).getProviderConfiguration(provider.name()));
         }
     }
 

apm-collector/apm-collector-core/src/test/java/org/skywalking/apm/collector/core/module/ModuleAProvider.java

@@ -34,10 +34,10 @@ public class ModuleAProvider extends ModuleProvider {
 
     @Override public void prepare(Properties config) throws ServiceNotProvidedException {
         this.registerServiceImplementation(BaseModuleA.ServiceABusiness1.class, new ModuleABusiness1Impl());
+        this.registerServiceImplementation(BaseModuleA.ServiceABusiness2.class, new ModuleABusiness2Impl());
     }
 
     @Override public void start(Properties config) throws ServiceNotProvidedException {
-        this.registerServiceImplementation(BaseModuleA.ServiceABusiness2.class, new ModuleABusiness2Impl());
     }
 
     @Override public void notifyAfterCompleted() throws ServiceNotProvidedException {

apm-collector/apm-collector-core/src/test/java/org/skywalking/apm/collector/core/module/ModuleBProvider.java

@@ -34,10 +34,10 @@ public class ModuleBProvider extends ModuleProvider {
 
     @Override public void prepare(Properties config) throws ServiceNotProvidedException {
         this.registerServiceImplementation(BaseModuleB.ServiceBBusiness1.class, new ModuleBBusiness1Impl());
+        this.registerServiceImplementation(BaseModuleB.ServiceBBusiness2.class, new ModuleBBusiness2Impl());
     }
 
     @Override public void start(Properties config) throws ServiceNotProvidedException {
-        this.registerServiceImplementation(BaseModuleB.ServiceBBusiness2.class, new ModuleBBusiness2Impl());
     }
 
     @Override public void notifyAfterCompleted() throws ServiceNotProvidedException {