user_id field added for log

log.md

@@ -26,7 +26,7 @@
 
 ## 日志示例
 
-    {"SYS": {"http_verb":"POST", "action": "/api/topic/create", "log_host": "10.127.158.29", "cl_id": "861342028123987123", "session_id": "cx123nfglxkdzlfjadwrsdnvsd34z", "cl_type": "ios", "cl_ver": "5.2.1", "channel": "mingxingyichu", "user_ip":"106.187.42.233"}, "LEVEL": "INFO", "APP": {"minami": "kotori", "hello": "world"}, "TIMER": {"total": 123.456, "get_user_from_context": 78.9}, "LOGID": "", "TIME": "2015-10-14T17:13:20+08:00", "MODULE":"gaia"}
+    {"SYS": {"http_verb":"POST", "action": "/api/topic/create", "log_host": "10.127.158.29", "cl_id": "861342028123987123", "session_id": "cx123nfglxkdzlfjadwrsdnvsd34z", "user_id":123456, "cl_type": "ios", "cl_ver": "5.2.1", "channel": "mingxingyichu", "user_ip":"106.187.42.233"}, "LEVEL": "INFO", "APP": {"minami": "kotori", "hello": "world"}, "TIMER": {"total": 123.456, "get_user_from_context": 78.9}, "LOGID": "", "TIME": "2015-10-14T17:13:20+08:00", "MODULE":"gaia"}
 
 ## 日志字段
 
@@ -64,6 +64,7 @@
     *   `cl_id`: 设备标识，android取`device_id`，ios取`idfa`。
     *   `channel`: 请求渠道，客户端取包名即`channel`字段。pc和m站需要具体分析，若请求的GET参数中带有`channel`参数，需要填入该字段。
     *   `session_id`: 用户登陆后必须填写。否则不填写。
+    *   `user_id`: 用户登陆后必须填写。否则不填写。
     *   `log_host`: 打印该日志所在机器的内网IP。
     *   `user_ip`: 用户的外网IP。
     *   `errno`: 错误号。无错误填0。出错或出现未知异常时要求填写非0值。