add EHOSTDOWN in error_code.md

docs/cn/error_code.md

@@ -27,6 +27,7 @@ brpc中常见错误的打印内容列表如下：
 | -------------- | ---- | ---- | ---------------------------------------- | ---------------------------------------- |
 | EAGAIN         | 11   | 是    | 同时发送的请求过多。软限，很少出现。                       | Resource temporarily unavailable         |
 | ETIMEDOUT      | 110  | 是    | 连接超时。                                    | Connection timed out                     |
+| EHOSTDOWN      | 112  | 是    | 找不到可用的server。server可能停止服务了，也可能正在退出中(返回了ELOGOFF)。 | "Fail to select server from …"  "Not connected to … yet" |
 | ENOSERVICE     | 1001 | 否    | 找不到服务，不太出现，一般会返回ENOMETHOD。               |                                          |
 | ENOMETHOD      | 1002 | 否    | 找不到方法。                                   | 形式广泛，常见如"Fail to find method=..."        |
 | EREQUEST       | 1003 | 否    | request序列化错误，client端和server端都可能设置        | 形式广泛："Missing required fields in request: …" "Fail to parse request message, …"  "Bad request" |

docs/en/error_code.md

@@ -21,10 +21,11 @@ All error codes in brpc are defined in [errno.proto](https://github.com/brpc/brp
 
 Following table shows common error codes and their descriptions: 
 
-| Error Code     | Value | Retriable | Description                              | Logging message                          |
-| -------------- | ----- | --------- | ---------------------------------------- | ---------------------------------------- |
+| Error Code     | Value | Retry | Description                              | Logging message                          |
+| -------------- | ----- | ----- | ---------------------------------------- | ---------------------------------------- |
 | EAGAIN         | 11    | Yes   | Too many requests at the same time, hardly happening as it's a soft limit. | Resource temporarily unavailable         |
 | ETIMEDOUT      | 110   | Yes   | Connection timeout.                      | Connection timed out                     |
+| EHOSTDOWN      | 112   | Yes   | No available server to send request. The servers may be stopped or stopping(returning ELOGOFF). | "Fail to select server from …"  "Not connected to … yet" |
 | ENOSERVICE     | 1001  | No    | Can't locate the service, hardly happening and usually being ENOMETHOD instead |                                          |
 | ENOMETHOD      | 1002  | No    | Can't locate the method.                 | Misc forms, common ones are "Fail to find method=…" |
 | EREQUEST       | 1003  | No    | fail to serialize the request, may be set on either client-side or server-side | Misc forms: "Missing required fields in request: …" "Fail to parse request message, …"  "Bad request" |