diff --git a/docs/about-counter.md b/docs/about-counter.md
index a15ac85f..75ad1e5c 100644
--- a/docs/about-counter.md
+++ b/docs/about-counter.md
@@ -97,7 +97,7 @@ counter->start()调用可以放在for循环之前。counter只要被创建，就
 # Server与其它异步引擎结合使用
 
 某些情况下，我们的server可能需要调用非本框架的异步客户端等待结果。简单的方法我们可以在process里同步等待，通过条件变量来唤醒。  
-这个做的缺点是我们占用了一个处理线程，把其它框架的异步客户端变为同步客户端。但通过counter的方法，我们可以不占线程地等待。
+这么做的缺点是我们占用了一个处理线程，把其它框架的异步客户端变为同步客户端。但通过counter，我们可以不占线程地等待。  
 方法很简单：
 ~~~cpp
 
@@ -120,6 +120,7 @@ void process(WFHttpTask *task)
 }
 ~~~
 在这里，我们可以把server任务所在的series理解为一个协程，而目标值为1的counter，可以理解为一个条件变量。  
+Counter的缺点是count操作不传递数据。如果业务有数据传达的需求，可以使用[Mailbox任务](https://github.com/sogou/workflow/blob/master/src/factory/WFTaskFactory.h#L268)。  
 
 # 命名计数器
 
diff --git a/src/client/WFConsulClient.cc b/src/client/WFConsulClient.cc
index 1a9a65e0..4f80be99 100644
--- a/src/client/WFConsulClient.cc
+++ b/src/client/WFConsulClient.cc
@@ -493,8 +493,6 @@ static bool create_tagged_address(const ConsulAddress& consul_address,
 		return false;
 
 	json_object_t *obj = json_value_object(val);
-	if (!obj)
-		return false;
 
 	if (!json_object_append(obj, "Address", JSON_VALUE_STRING,
 							consul_address.first.c_str()))
@@ -520,8 +518,6 @@ static bool create_health_check(const ConsulConfig& config, json_object_t *obj)
 		return false;
 
 	obj = json_value_object(val);
-	if (!obj)
-		return false;
 
 	str = config.get_check_name();
 	if (!json_object_append(obj, "Name", JSON_VALUE_STRING, str.c_str()))
@@ -550,8 +546,6 @@ static bool create_health_check(const ConsulConfig& config, json_object_t *obj)
 			return false;
 
 		json_object_t *header_obj = json_value_object(val);
-		if (!header_obj)
-			return false;
 
 		for (const auto& header : *config.get_http_headers())
 		{
@@ -561,8 +555,6 @@ static bool create_health_check(const ConsulConfig& config, json_object_t *obj)
 				return false;
 
 			json_array_t *arr = json_value_array(val);
-			if (!arr)
-				return false;
 
 			for (const auto& value : header.second)
 			{
@@ -638,8 +630,6 @@ static bool create_register_request(const json_value_t *root,
 		return false;
 
 	json_array_t *arr = json_value_array(val);
-	if (!arr)
-		return false;
 
 	for (const auto& tag : service->tags)
 	{
@@ -660,8 +650,6 @@ static bool create_register_request(const json_value_t *root,
 		return false;
 
 	json_object_t *meta_obj = json_value_object(val);
-	if (!meta_obj)
-		return false;
 
 	for (const auto& meta_kv : service->meta)
 	{
@@ -820,11 +808,11 @@ static bool parse_discover_node(const json_object_t *obj,
 	}
 
 	val = json_object_find("CreateIndex", obj);
-	if (val)
+	if (val && json_value_type(val) == JSON_VALUE_NUMBER)
 		instance->create_index = json_value_number(val);
 
 	val = json_object_find("ModifyIndex", obj);
-	if (val)
+	if (val && json_value_type(val) == JSON_VALUE_NUMBER)
 		instance->modify_index = json_value_number(val);
 
 	return true;
@@ -860,7 +848,7 @@ static bool parse_tagged_address(const char *name,
 
 	tagged_address.first = str;
 	val = json_object_find("Port", obj);
-	if (!val)
+	if (!val || json_value_type(val) != JSON_VALUE_NUMBER)
 		return false;
 
 	tagged_address.second = json_value_number(val);
diff --git a/src/kernel/Communicator.cc b/src/kernel/Communicator.cc
index dcd2774f..d5fd7a10 100644
--- a/src/kernel/Communicator.cc
+++ b/src/kernel/Communicator.cc
@@ -1112,19 +1112,12 @@ void Communicator::handler_thread_routine(void *context)
 			break;
 		default:
 			free(res);
-			if (comm->thrdpool)
-				thrdpool_exit(comm->thrdpool);
-			continue;
+			thrdpool_exit(comm->thrdpool);
+			return;
 		}
 
 		free(res);
 	}
-
-	if (!comm->thrdpool)
-	{
-		mpoller_destroy(comm->mpoller);
-		msgqueue_destroy(comm->msgqueue);
-	}
 }
 
 int Communicator::append_message(const void *buf, size_t *size,
@@ -1478,15 +1471,12 @@ int Communicator::init(size_t poller_threads, size_t handler_threads)
 
 void Communicator::deinit()
 {
-	int in_handler = this->is_handler_thread();
-
 	this->stop_flag = 1;
 	mpoller_stop(this->mpoller);
 	msgqueue_set_nonblock(this->msgqueue);
 	thrdpool_destroy(NULL, this->thrdpool);
-	this->thrdpool = NULL;
-	if (!in_handler)
-		Communicator::handler_thread_routine(this);
+	mpoller_destroy(this->mpoller);
+	msgqueue_destroy(this->msgqueue);
 }
 
 int Communicator::nonblock_connect(CommTarget *target)
diff --git a/src/nameservice/WFDnsResolver.cc b/src/nameservice/WFDnsResolver.cc
index b718e0bf..a1334000 100644
--- a/src/nameservice/WFDnsResolver.cc
+++ b/src/nameservice/WFDnsResolver.cc
@@ -211,10 +211,8 @@ using thread_dns_callback_t = std::function<void (ThreadDnsTask *)>;
 
 struct DnsContext
 {
-	int state;
-	int error;
-	int eai_error;
 	unsigned short port;
+	int eai_error;
 	struct addrinfo *ai;
 };
 
@@ -647,8 +645,8 @@ void WFResolverTask::dns_single_callback(void *net_dns_task)
 	}
 	else
 	{
-		this->state = dns_task->get_state();
-		this->error = dns_task->get_error();
+		this->state = WFT_STATE_DNS_ERROR;
+		this->error = EAI_AGAIN;
 	}
 
 	task_callback();
@@ -660,57 +658,50 @@ void WFResolverTask::dns_partial_callback(void *net_dns_task)
 	WFGlobal::get_dns_respool()->post(NULL);
 
 	struct DnsContext *ctx = (struct DnsContext *)dns_task->user_data;
+
 	ctx->ai = NULL;
-	ctx->state = dns_task->get_state();
-	ctx->error = dns_task->get_error();
-	if (ctx->state == WFT_STATE_SUCCESS)
+	if (dns_task->get_state() == WFT_STATE_SUCCESS)
 	{
 		protocol::DnsResponse *resp = dns_task->get_resp();
 		ctx->eai_error = protocol::DnsUtil::getaddrinfo(resp, ctx->port,
 														&ctx->ai);
 	}
 	else
-		ctx->eai_error = EAI_NONAME;
+		ctx->eai_error = EAI_AGAIN;
 }
 
 void WFResolverTask::dns_parallel_callback(const void *parallel)
 {
 	const ParallelWork *pwork = (const ParallelWork *)parallel;
-	struct DnsContext *c4 = (struct DnsContext *)(pwork->get_context());
+	struct DnsContext *c4 = (struct DnsContext *)pwork->get_context();
 	struct DnsContext *c6 = c4 + 1;
-	DnsOutput out;
 
-	if (c4->state != WFT_STATE_SUCCESS && c6->state != WFT_STATE_SUCCESS)
+	if (c4->eai_error == 0 || c6->eai_error == 0)
 	{
-		this->state = c4->state;
-		this->error = c4->error;
-	}
-	else if (c4->eai_error != 0 && c6->eai_error != 0)
-	{
-		DnsRoutine::create(&out, c4->eai_error, NULL);
+		struct addrinfo *ai = NULL;
+		struct addrinfo **pai = &ai;
+		DnsOutput out;
+
+		*pai = c4->ai;
+		while (*pai)
+			pai = &(*pai)->ai_next;
+
+		*pai = c6->ai;
+		DnsRoutine::create(&out, 0, ai);
 		dns_callback_internal(&out, dns_ttl_default_, dns_ttl_min_);
 	}
 	else
 	{
-		struct addrinfo *ai = NULL;
-		struct addrinfo **pai = &ai;
+		int eai_error = c4->eai_error;
 
-		if (c4->ai != NULL)
-		{
-			*pai = c4->ai;
-			while (*pai)
-				pai = &(*pai)->ai_next;
-		}
+		if (c6->eai_error == EAI_AGAIN)
+			eai_error = EAI_AGAIN;
 
-		if (c6->ai != NULL)
-			*pai = c6->ai;
-
-		DnsRoutine::create(&out, 0, ai);
-		dns_callback_internal(&out, dns_ttl_default_, dns_ttl_min_);
+		this->state = WFT_STATE_DNS_ERROR;
+		this->error = eai_error;
 	}
 
-	delete[] c4;
-
+	delete []c4;
 	task_callback();
 }
 
diff --git a/src/util/json_parser.c b/src/util/json_parser.c
index 647b3ec7..9d3f418e 100644
--- a/src/util/json_parser.c
+++ b/src/util/json_parser.c
@@ -1180,6 +1180,12 @@ const json_value_t *json_object_prev_value(const json_value_t *val,
 	return &list_entry(pos->prev, json_member_t, list)->value;
 }
 
+const char *json_object_value_name(const json_value_t *val,
+								   const json_object_t *obj)
+{
+	return list_entry(val, json_member_t, value)->name;
+}
+
 static const json_value_t *__json_object_insert(const char *name,
 												int type, va_list ap,
 												struct list_head *pos,
diff --git a/src/util/json_parser.h b/src/util/json_parser.h
index 4f21ebd4..5ca97c75 100644
--- a/src/util/json_parser.h
+++ b/src/util/json_parser.h
@@ -60,6 +60,8 @@ const char *json_object_prev_name(const char *name,
 								  const json_object_t *obj);
 const json_value_t *json_object_prev_value(const json_value_t *val,
 										   const json_object_t *obj);
+const char *json_object_value_name(const json_value_t *val,
+								   const json_object_t *obj);
 const json_value_t *json_object_append(json_object_t *obj,
 									   const char *name,
 									   int type, ...);