Resolves #61: Enhance exception trace in Sentinel Dubbo Adapter

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

sentinel-adapter/sentinel-dubbo-adapter/src/main/java/com/alibaba/csp/sentinel/adapter/dubbo/SentinelDubboConsumerFilter.java

@@ -57,7 +57,13 @@ public class SentinelDubboConsumerFilter extends AbstractDubboFilter implements
             ContextUtil.enter(resourceName);
             interfaceEntry = SphU.entry(invoker.getInterface().getName(), EntryType.OUT);
             methodEntry = SphU.entry(resourceName, EntryType.OUT);
-            return invoker.invoke(invocation);
+            Result result = invoker.invoke(invocation);
+            if (result.hasException()) {
+                // Record common exception.
+                Tracer.trace(result.getException());
+            }
+            return result;
         } catch (BlockException e) {
             return DubboFallbackRegistry.getConsumerFallback().handle(invoker, invocation, e);
         } catch (RpcException e) {

sentinel-adapter/sentinel-dubbo-adapter/src/main/java/com/alibaba/csp/sentinel/adapter/dubbo/SentinelDubboProviderFilter.java

@@ -63,7 +63,11 @@ public class SentinelDubboProviderFilter extends AbstractDubboFilter implements
             interfaceEntry = SphU.entry(interfaceName, EntryType.IN);
             methodEntry = SphU.entry(resourceName, EntryType.IN, 1, invocation.getArguments());
 
-            return invoker.invoke(invocation);
+            Result result = invoker.invoke(invocation);
+            if (result.hasException()) {
+                Tracer.trace(result.getException());
+            }
+            return result;
         } catch (BlockException e) {
             return DubboFallbackRegistry.getProviderFallback().handle(invoker, invocation, e);
         } catch (RpcException e) {