diff --git a/cache/cache_evbase_client.cpp b/cache/cache_evbase_client.cpp
index f880a4b..40de5c2 100644
--- a/cache/cache_evbase_client.cpp
+++ b/cache/cache_evbase_client.cpp
@@ -115,13 +115,13 @@ static int32_t iothread_notify_event(int32_t socket_fd, void *content, int32_t l
 		}
 		if(res <= 0)
 		{
-			printf("log_error: select io res=%d, error: %s", res, strerror(errno));
+			printf("log_error: select io res=%d, error: %s\n", res, strerror(errno));
 			return -1;
 		}
 
 		if(FD_ISSET(socket_fd, &e_set))
 		{
-			printf("log_error: select io is in efds, error: %s", strerror(errno));
+			printf("log_error: select io is in efds, error: %s\n", strerror(errno));
 			return -2;
 		}
 
@@ -250,15 +250,11 @@ void cache_evbase_update_end(struct cache_evbase_ctx *ctx_asyn)
 	buffer->ctx_asyn = ctx_asyn;
 	buffer->cmd_type = CACHE_ASYN_UPLOAD_END;
 	
-	if(iothread_notify_event(ctx_asyn->instance_asyn->notify_sendfd, &buffer, sizeof(void *), 0) != sizeof(void *))
+	if(iothread_notify_event(ctx_asyn->instance_asyn->notify_sendfd, &buffer, sizeof(void *), 2) != sizeof(void *))
 	{
 		if(!ctx_asyn->ctx->fail_state)
 		{
-			ctx_asyn->ctx->fail_state = true;
-			if(ctx_asyn->ctx->future != NULL)
-			{
-				promise_failed(future_to_promise(ctx_asyn->ctx->future), FUTURE_ERROR_CANCEL, "write sockpair error");
-			}
+			tango_cache_set_fail_state(ctx_asyn->ctx, CACHE_ERR_SOCKPAIR);
 		}
 		tango_cache_ctx_destroy(ctx_asyn->ctx);
 		cache_asyn_ctx_destroy(ctx_asyn);
@@ -289,12 +285,11 @@ int cache_evbase_update_frag_data(struct cache_evbase_ctx *ctx_asyn, enum PUT_ME
 	buffer->ctx_asyn = ctx_asyn;
 	buffer->cmd_type = CACHE_ASYN_UPLOAD_FRAG_DATA;
 
-	if(iothread_notify_event(ctx_asyn->instance_asyn->notify_sendfd, &buffer, sizeof(void *), 0) != sizeof(void *))
+	if(iothread_notify_event(ctx_asyn->instance_asyn->notify_sendfd, &buffer, sizeof(void *), 2) != sizeof(void *))
 	{
-		ctx_asyn->ctx->fail_state = true;
-		if(ctx_asyn->ctx->future != NULL)
+		if(!ctx_asyn->ctx->fail_state)
 		{
-			promise_failed(future_to_promise(ctx_asyn->ctx->future), FUTURE_ERROR_CANCEL, "write sockpair error");
+			tango_cache_set_fail_state(ctx_asyn->ctx, CACHE_ERR_SOCKPAIR);
 		}
 		free(buffer->data);
 		free(buffer);
@@ -317,12 +312,11 @@ int cache_evbase_update_frag_evbuf(struct cache_evbase_ctx *ctx_asyn, struct evb
 	buffer->evbuf = evbuffer_new();
 	evbuffer_add_buffer(buffer->evbuf, evbuf);
 
-	if(iothread_notify_event(ctx_asyn->instance_asyn->notify_sendfd, &buffer, sizeof(void *), 0) != sizeof(void *))
+	if(iothread_notify_event(ctx_asyn->instance_asyn->notify_sendfd, &buffer, sizeof(void *), 2) != sizeof(void *))
 	{
-		ctx_asyn->ctx->fail_state = true;
-		if(ctx_asyn->ctx->future != NULL)
+		if(!ctx_asyn->ctx->fail_state)
 		{
-			promise_failed(future_to_promise(ctx_asyn->ctx->future), FUTURE_ERROR_CANCEL, "write sockpair error");
+			tango_cache_set_fail_state(ctx_asyn->ctx, CACHE_ERR_SOCKPAIR);
 		}
 		evbuffer_free(buffer->evbuf);
 		free(buffer);
@@ -352,9 +346,9 @@ struct cache_evbase_ctx *cache_evbase_update_start(struct cache_evbase_instance
 	buffer->cmd_type = CACHE_ASYN_UPLOAD_START;
 
 	//事件通知仅为了增加统计信息
-	if(iothread_notify_event(instance->notify_sendfd, &buffer, sizeof(void *), 0) != sizeof(void *))
+	if(iothread_notify_event(instance->notify_sendfd, &buffer, sizeof(void *), 2) != sizeof(void *))
 	{
-		ctx_asyn->ctx->fail_state = true;
+		tango_cache_set_fail_state(ctx_asyn->ctx, CACHE_ERR_SOCKPAIR);
 		tango_cache_ctx_destroy(ctx_asyn->ctx);
 		cache_asyn_ctx_destroy(ctx_asyn);
 		free(buffer);
@@ -398,11 +392,11 @@ int cache_evbase_upload_once_data(struct cache_evbase_instance *instance, struct
 	buffer->ctx_asyn = ctx_asyn;
 	buffer->cmd_type = CACHE_ASYN_UPLOAD_ONCE_DATA;
 	
-	if(iothread_notify_event(instance->notify_sendfd, &buffer, sizeof(void *), 0) != sizeof(void *))
+	if(iothread_notify_event(instance->notify_sendfd, &buffer, sizeof(void *), 2) != sizeof(void *))
 	{
 		free(buffer->data);
 		free(buffer);
-		ctx_asyn->ctx->fail_state = true;
+		tango_cache_set_fail_state(ctx_asyn->ctx, CACHE_ERR_SOCKPAIR);
 		tango_cache_ctx_destroy(ctx);
 		cache_asyn_ctx_destroy(ctx_asyn);
 		return -2;
@@ -437,11 +431,11 @@ int cache_evbase_upload_once_evbuf(struct cache_evbase_instance *instance, struc
 	buffer->evbuf = evbuffer_new();
 	evbuffer_add_buffer(buffer->evbuf, evbuf);
 
-	if(iothread_notify_event(instance->notify_sendfd, &buffer, sizeof(void *), 0) != sizeof(void *))
+	if(iothread_notify_event(instance->notify_sendfd, &buffer, sizeof(void *), 2) != sizeof(void *))
 	{
 		evbuffer_free(buffer->evbuf);
 		free(buffer);
-		ctx_asyn->ctx->fail_state = true;
+		tango_cache_set_fail_state(ctx_asyn->ctx, CACHE_ERR_SOCKPAIR);
 		tango_cache_ctx_destroy(ctx);
 		cache_asyn_ctx_destroy(ctx_asyn);
 		return -2;
@@ -467,8 +461,10 @@ int cache_evbase_fetch_object(struct cache_evbase_instance *instance, struct fut
 	buffer->ctx_asyn = ctx_asyn;
 	buffer->cmd_type = CACHE_ASYN_FETCH;
 
-	if(iothread_notify_event(instance->notify_sendfd, &buffer, sizeof(void *), 0) != sizeof(void *))
+	if(iothread_notify_event(instance->notify_sendfd, &buffer, sizeof(void *), 2) != sizeof(void *))
 	{
+		tango_cache_set_fail_state(ctx_asyn->ctx, CACHE_ERR_SOCKPAIR);
+		promise_failed(future_to_promise(future), FUTURE_ERROR_CANCEL, tango_cache_get_errstring(ctx_asyn->ctx));
 		tango_cache_ctx_destroy(ctx_asyn->ctx);
 		cache_asyn_ctx_destroy(ctx_asyn);
 		free(buffer);
@@ -496,9 +492,13 @@ int cache_evbase_delete_object(struct cache_evbase_instance *instance, struct fu
 	buffer->cmd_type = CACHE_ASYN_DELETE;
 
 	//参考Unix高级编程432页关于多线程写的安全性描述
-	if(iothread_notify_event(instance->notify_sendfd, &buffer, sizeof(void *), 0) != sizeof(void *))
+	if(iothread_notify_event(instance->notify_sendfd, &buffer, sizeof(void *), 2) != sizeof(void *))
 	{
-		ctx_asyn->ctx->fail_state = true;
+		tango_cache_set_fail_state(ctx_asyn->ctx, CACHE_ERR_SOCKPAIR);
+		if(future != NULL)
+		{
+			promise_failed(future_to_promise(future), FUTURE_ERROR_CANCEL, tango_cache_get_errstring(ctx_asyn->ctx));
+		}
 		tango_cache_ctx_destroy(ctx_asyn->ctx);
 		cache_asyn_ctx_destroy(ctx_asyn);
 		free(buffer);
diff --git a/cache/include/tango_cache_client.h b/cache/include/tango_cache_client.h
index 90e0f28..268cdf5 100644
--- a/cache/include/tango_cache_client.h
+++ b/cache/include/tango_cache_client.h
@@ -17,6 +17,8 @@ enum CACHE_ERR_CODE
 	CACHE_OUTOF_MEMORY,//当前内存占用超过限制，查看MAX_USED_MEMORY_SIZE_MB是否过小或者当前上传速率跟不上调用者的速率
 	CACHE_ERR_CURL,
 	CACHE_ERR_WIREDLB,
+	CACHE_ERR_SOCKPAIR,
+	CACHE_ERR_INTERNAL,
 };
 
 enum PUT_MEMORY_COPY_WAY
diff --git a/cache/pangu_tango_cache.a b/cache/pangu_tango_cache.a
index 0094000..20e2fea 100644
Binary files a/cache/pangu_tango_cache.a and b/cache/pangu_tango_cache.a differ
diff --git a/cache/tango_cache_client.cpp b/cache/tango_cache_client.cpp
index f25177e..2938552 100644
--- a/cache/tango_cache_client.cpp
+++ b/cache/tango_cache_client.cpp
@@ -54,6 +54,26 @@ enum CACHE_ERR_CODE tango_cache_ctx_error(const struct tango_cache_instance *ins
 	return instance->error_code;
 }
 
+void tango_cache_set_fail_state(struct tango_cache_ctx *ctx, enum CACHE_ERR_CODE error_code)
+{
+	ctx->fail_state = true;
+	ctx->error_code = error_code;
+}
+
+const char *tango_cache_get_errstring(const struct tango_cache_ctx *ctx)
+{
+	switch(ctx->error_code)
+	{
+		case CACHE_CACHE_MISS:	return "cache not hit";
+		case CACHE_TIMEOUT:		return "cache not fresh";
+		case CACHE_OUTOF_MEMORY:return "outof memory";
+		case CACHE_ERR_WIREDLB:	return "wiredlb error";
+		case CACHE_ERR_SOCKPAIR:return "socketpair error";
+		case CACHE_ERR_INTERNAL:return "cache Expires or x-amz-meta-lm not found";
+		default: return ctx->error;
+	}
+}
+
 void tango_cache_get_statistics(const struct tango_cache_instance *instance, struct cache_statistics *out)
 {
 	out->get_recv_num = instance->statistic.get_recv_num;
@@ -182,7 +202,7 @@ void tango_cache_ctx_destroy(struct tango_cache_ctx *ctx)
 			{
 				if(ctx->fail_state)
 				{
-					promise_failed(future_to_promise(ctx->future), FUTURE_ERROR_CANCEL, ctx->error);
+					promise_failed(future_to_promise(ctx->future), FUTURE_ERROR_CANCEL, tango_cache_get_errstring(ctx));
 				}			
 				else
 				{
@@ -313,7 +333,7 @@ struct tango_cache_ctx *tango_cache_update_prepare(struct tango_cache_instance *
 	{
 		ctx->headers = curl_slist_append(ctx->headers, "Content-Type:");
 	}
-	ctx->headers = curl_slist_append(ctx->headers, "Expect:");
+	//ctx->headers = curl_slist_append(ctx->headers, "Expect:"); //不可以添加？curl_multi_socket_action会卡住
 	//其他定义的头部，GET时会原样返回
 	if(meta->usertag_len>0 && meta->usertag_len<=USER_TAG_MAX_LEN)
 	{
diff --git a/cache/tango_cache_client_in.h b/cache/tango_cache_client_in.h
index 2c6295d..3c2ab00 100644
--- a/cache/tango_cache_client_in.h
+++ b/cache/tango_cache_client_in.h
@@ -130,6 +130,8 @@ void easy_string_savedata(struct easy_string *estr, const char *data, size_t len
 void easy_string_destroy(struct easy_string *estr);
 
 void tango_cache_ctx_destroy(struct tango_cache_ctx *ctx);
+void tango_cache_set_fail_state(struct tango_cache_ctx *ctx, enum CACHE_ERR_CODE error_code);
+const char *tango_cache_get_errstring(const struct tango_cache_ctx *ctx);
 
 struct tango_cache_ctx *tango_cache_update_prepare(struct tango_cache_instance *instance, struct future* future, struct tango_cache_meta *meta);
 struct tango_cache_ctx *tango_cache_fetch_prepare(struct tango_cache_instance *instance, struct future* future, struct tango_cache_meta *meta);
diff --git a/cache/tango_cache_transfer.cpp b/cache/tango_cache_transfer.cpp
index fd76937..8945abb 100644
--- a/cache/tango_cache_transfer.cpp
+++ b/cache/tango_cache_transfer.cpp
@@ -157,8 +157,7 @@ static size_t curl_write_uploadID_cb(void *ptr, size_t size, size_t count, void
 		code = curl_easy_getinfo(ctx->curl, CURLINFO_RESPONSE_CODE, &ctx->res_code);
 		if(code != CURLE_OK || ctx->res_code!=200L)
 		{
-			ctx->fail_state = true;
-			ctx->error_code = CACHE_ERR_CURL;
+			tango_cache_set_fail_state(ctx, CACHE_ERR_CURL);
 			if(code != CURLE_OK) MESA_HANDLE_RUNTIME_LOGV2(ctx->instance->runtime_log, RLOG_LV_DEBUG, "%s", ctx->error);
 			return size*count;
 		}
@@ -182,6 +181,7 @@ int curl_get_minio_uploadID(struct tango_cache_ctx *ctx)
 	snprintf(minio_url, 256, "http://%s/%s/%s?uploads", ctx->hostaddr, ctx->instance->bucketname, ctx->object_key);
 	curl_easy_setopt(ctx->curl, CURLOPT_POST, 1L);
 	curl_easy_setopt(ctx->curl, CURLOPT_URL, minio_url);
+
 	curl_easy_setopt(ctx->curl, CURLOPT_USERAGENT, "aws-sdk-cpp/1.5.24 Linux/3.10.0-327.el7.x86_64 x86_64 pangu_cache");
 	curl_easy_setopt(ctx->curl, CURLOPT_NOSIGNAL,1L);
 	curl_easy_setopt(ctx->curl, CURLOPT_WRITEFUNCTION, curl_write_uploadID_cb);
@@ -321,8 +321,7 @@ bool cache_kick_upload_minio_multipart(struct tango_cache_ctx *ctx, size_t block
 	
 	if(ret <= 0)
 	{
-		ctx->fail_state = true;
-		ctx->error_code = CACHE_ERR_CURL;
+		tango_cache_set_fail_state(ctx, CACHE_ERR_CURL);
 		return false;
 	}
 	return true;
@@ -339,8 +338,7 @@ int http_put_complete_part_evbuf(struct tango_cache_ctx *ctx)
 		ret = http_put_bodypart_request_evbuf(ctx, true);
 		if(ret <= 0)
 		{
-			ctx->fail_state = true;
-			ctx->error_code = CACHE_ERR_CURL;
+			tango_cache_set_fail_state(ctx, CACHE_ERR_CURL);
 			tango_cache_ctx_destroy(ctx);
 		}
 	}
@@ -381,8 +379,7 @@ int cache_kick_upload_minio_end(struct tango_cache_ctx *ctx)
 					}
 					else
 					{
-						ctx->fail_state = true;
-						ctx->error_code = CACHE_ERR_CURL;
+						tango_cache_set_fail_state(ctx, CACHE_ERR_CURL);
 						tango_cache_ctx_destroy(ctx);
 					}
 				}
@@ -391,8 +388,7 @@ int cache_kick_upload_minio_end(struct tango_cache_ctx *ctx)
 					ret = http_put_bodypart_request_evbuf(ctx, false);
 					if(ret <= 0)
 					{
-						ctx->fail_state = true;
-						ctx->error_code = CACHE_ERR_CURL;
+						tango_cache_set_fail_state(ctx, CACHE_ERR_CURL);
 						if(cache_cancel_upload_minio(ctx))
 						{
 							ctx->put.state = PUT_STATE_CANCEL;
@@ -422,8 +418,7 @@ void tango_cache_curl_put_done(struct tango_cache_ctx *ctx, CURLcode res, long r
 			if(res!=CURLE_OK||res_code!=200L|| ctx->fail_state || !parse_uploadID_xml(ctx->response.buff, ctx->response.len, &ctx->put.uploadID))
 			{
 				easy_string_destroy(&ctx->response);
-				ctx->error_code = CACHE_ERR_CURL;
-				ctx->fail_state = true;
+				tango_cache_set_fail_state(ctx, CACHE_ERR_CURL);
 				if(res != CURLE_OK) MESA_HANDLE_RUNTIME_LOGV2(ctx->instance->runtime_log, RLOG_LV_DEBUG, "%s", ctx->error);
 				if(ctx->put.close_state)
 				{
@@ -452,8 +447,7 @@ void tango_cache_curl_put_done(struct tango_cache_ctx *ctx, CURLcode res, long r
 		case PUT_STATE_PART:
 			if(res != CURLE_OK || res_code!=200L)
 			{
-				ctx->fail_state = true;
-				ctx->error_code = CACHE_ERR_CURL;
+				tango_cache_set_fail_state(ctx, CACHE_ERR_CURL);
 				if(res != CURLE_OK) MESA_HANDLE_RUNTIME_LOGV2(ctx->instance->runtime_log, RLOG_LV_DEBUG, "%s", ctx->error);
 			}
 			if(ctx->fail_state)
@@ -491,8 +485,7 @@ void tango_cache_curl_put_done(struct tango_cache_ctx *ctx, CURLcode res, long r
 		case PUT_STATE_END:
 			if(res != CURLE_OK || res_code!=200L)
 			{
-				ctx->fail_state = true;
-				ctx->error_code = CACHE_ERR_CURL;
+				tango_cache_set_fail_state(ctx, CACHE_ERR_CURL);
 				if(res != CURLE_OK) MESA_HANDLE_RUNTIME_LOGV2(ctx->instance->runtime_log, RLOG_LV_DEBUG, "%s", ctx->error);
 			}
 			tango_cache_ctx_destroy(ctx);
@@ -600,8 +593,8 @@ void tango_cache_curl_get_done(struct tango_cache_ctx *ctx, CURLcode res, long r
 			{
 				if(res!=CURLE_OK || res_code!=200L)
 				{
-					ctx->error_code = (res!=CURLE_OK)?CACHE_ERR_CURL:CACHE_CACHE_MISS;
-					promise_failed(future_to_promise(ctx->future), FUTURE_ERROR_CANCEL, ctx->error);
+					tango_cache_set_fail_state(ctx, (res!=CURLE_OK)?CACHE_ERR_CURL:CACHE_CACHE_MISS);
+					promise_failed(future_to_promise(ctx->future), FUTURE_ERROR_CANCEL, tango_cache_get_errstring(ctx));
 				}
 				else
 				{
@@ -641,10 +634,9 @@ static size_t curl_get_response_body_cb(void *ptr, size_t size, size_t count, vo
 	
 	if(ctx->get.need_hdrs!=RESPONSE_HDR_ALL) //无Expires时
 	{
-		ctx->fail_state = true;
-		ctx->error_code = CACHE_ERR_CURL;
+		tango_cache_set_fail_state(ctx, CACHE_ERR_INTERNAL);
 		ctx->get.state	= GET_STATE_DELETE;
-		promise_failed(future_to_promise(ctx->future), FUTURE_ERROR_CANCEL, "cache Expires or x-amz-meta-lm not found");
+		promise_failed(future_to_promise(ctx->future), FUTURE_ERROR_CANCEL, tango_cache_get_errstring(ctx));
 		return size*count;
 	}
 
@@ -680,11 +672,10 @@ static bool check_expires_header(struct tango_cache_ctx *ctx, const char *expire
 	
 	if(time_gmt > ctx->get.expires) //缓存失效；TODO relative_age的含义是啥
 	{
-		ctx->fail_state = true;
-		ctx->error_code = CACHE_TIMEOUT;
+		tango_cache_set_fail_state(ctx, CACHE_TIMEOUT);
 		ctx->get.state  = GET_STATE_DELETE; //缓存失效时在下载完毕时触发删除动作
 		easy_string_destroy(&ctx->response);
-		promise_failed(future_to_promise(ctx->future), FUTURE_ERROR_CANCEL, "cache not fresh");
+		promise_failed(future_to_promise(ctx->future), FUTURE_ERROR_CANCEL, tango_cache_get_errstring(ctx));
 		return false;
 	}
 	return true;
@@ -700,10 +691,9 @@ static bool check_fresh_header(struct tango_cache_ctx *ctx)
 	now_gmt = get_gmtime_timestamp(time(NULL));
 	if(ctx->get.last_modify+ctx->get.max_age > now_gmt || now_gmt+ctx->get.min_fresh>ctx->get.expires)
 	{
-		ctx->fail_state = true;
-		ctx->error_code = CACHE_TIMEOUT;
+		tango_cache_set_fail_state(ctx, CACHE_TIMEOUT);
 		easy_string_destroy(&ctx->response);
-		promise_failed(future_to_promise(ctx->future), FUTURE_ERROR_CANCEL, "cache not fresh");
+		promise_failed(future_to_promise(ctx->future), FUTURE_ERROR_CANCEL, tango_cache_get_errstring(ctx));
 		return false;
 	}
 	return true;
@@ -716,9 +706,8 @@ static bool check_get_result_code(struct tango_cache_ctx *ctx)
 	code = curl_easy_getinfo(ctx->curl, CURLINFO_RESPONSE_CODE, &ctx->res_code);
 	if(code != CURLE_OK || ctx->res_code!=200L)
 	{
-		ctx->fail_state = true;
-		ctx->error_code = (code!=CURLE_OK)?CACHE_ERR_CURL:CACHE_CACHE_MISS;
-		promise_failed(future_to_promise(ctx->future), FUTURE_ERROR_CANCEL, (code!=CURLE_OK)?ctx->error:"cache not hit");
+		tango_cache_set_fail_state(ctx, (code!=CURLE_OK)?CACHE_ERR_CURL:CACHE_CACHE_MISS);
+		promise_failed(future_to_promise(ctx->future), FUTURE_ERROR_CANCEL, tango_cache_get_errstring(ctx));
 		return false;
 	}
 	return true;