Fix the issue that Hystrix plugin case NPE (#1293)

apm-sniffer/apm-sdk-plugin/hystrix-1.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/hystrix/v1/HystrixCommandGetFallbackInterceptor.java

@@ -36,7 +36,9 @@ public class HystrixCommandGetFallbackInterceptor implements InstanceMethodsArou
 
         AbstractSpan activeSpan = ContextManager.createLocalSpan(enhanceRequireObjectCache.getOperationNamePrefix() + "/Fallback");
         activeSpan.setComponent(ComponentsDefine.HYSTRIX);
-        ContextManager.continued(snapshot);
+        if (snapshot != null) {
+            ContextManager.continued(snapshot);
+        }
     }
 
     @Override

apm-sniffer/apm-sdk-plugin/hystrix-1.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/hystrix/v1/HystrixCommandRunInterceptor.java

@@ -41,7 +41,9 @@ public class HystrixCommandRunInterceptor implements InstanceMethodsAroundInterc
 
         AbstractSpan activeSpan = ContextManager.createLocalSpan(enhanceRequireObjectCache.getOperationNamePrefix() + "/Execution");
         activeSpan.setComponent(ComponentsDefine.HYSTRIX);
-        ContextManager.continued(snapshot);
+        if (snapshot != null) {
+            ContextManager.continued(snapshot);
+        }
         // Because of `fall back` method running in other thread. so we need capture concurrent span for tracing.
         enhanceRequireObjectCache.setContextSnapshot(ContextManager.capture());
 

apm-sniffer/apm-sdk-plugin/hystrix-1.x-plugin/src/main/java/org/apache/skywalking/apm/plugin/hystrix/v1/SWExecutionHookWrapper.java

@@ -41,7 +41,9 @@ public class SWExecutionHookWrapper extends HystrixCommandExecutionHook {
     public <T> void onStart(HystrixInvokable<T> commandInstance) {
         EnhancedInstance enhancedInstance = (EnhancedInstance)commandInstance;
         EnhanceRequireObjectCache enhanceRequireObjectCache = (EnhanceRequireObjectCache)enhancedInstance.getSkyWalkingDynamicField();
-        enhanceRequireObjectCache.setContextSnapshot(ContextManager.capture());
+        if (ContextManager.isActive()) {
+            enhanceRequireObjectCache.setContextSnapshot(ContextManager.capture());
+        }
         actual.onStart(commandInstance);
     }
 
@@ -166,7 +168,9 @@ public class SWExecutionHookWrapper extends HystrixCommandExecutionHook {
     @Override public <T> void onStart(HystrixCommand<T> commandInstance) {
         EnhancedInstance enhancedInstance = (EnhancedInstance)commandInstance;
         EnhanceRequireObjectCache enhanceRequireObjectCache = (EnhanceRequireObjectCache)enhancedInstance.getSkyWalkingDynamicField();
-        enhanceRequireObjectCache.setContextSnapshot(ContextManager.capture());
+        if (ContextManager.isActive()) {
+            enhanceRequireObjectCache.setContextSnapshot(ContextManager.capture());
+        }
         actual.onStart(commandInstance);
     }