使用Nginx+lua返回错误码并且返回自定义内容。

使用Nginx+lua返回错误码并且返回自定义内容。
使用ngx.exit(后端服务返回的httpcode)，如果后台返回的是500 等错误码的时候如下用法会有错误：

ngx.say(res.content)
ngx.exit(res.httpCode);

上面的代码在后端服务器返回非200的时候，会返回客户端 200，内容则是错误信息；日志显示大体是：在返回200之后，又设置成500 。

ngx.status = res.httpCode;
ngx.say(res.content);
ngx.exit(200);

上面的代码，会返回 500错误码和后端app返回的错误信息；
结论：
ngx.status 是设置http 相应码的。
ngx.exit(code)：官方文档如下

ngx.exit

syntax: ngx.exit(status)

context: rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua*, ngx.timer., balancer_by_lua, ssl_certificate_by_lua*, ssl_session_fetch_by_lua*, ssl_session_store_by_lua*

When status >= 200 (i.e., ngx.HTTP_OK and above), it will interrupt the execution of the current request and return status code to nginx.

When status == 0 (i.e., ngx.OK), it will only quit the current phase handler (or the content handler if the content_by_lua* directive is used) and continue to run later phases (if any) for the current request.

The status argument can be ngx.OK, ngx.ERROR, ngx.HTTP_NOT_FOUND, ngx.HTTP_MOVED_TEMPORARILY, or other HTTP status constants.

To return an error page with custom contents, use code snippets like this:

 ngx.status = ngx.HTTP_GONE
 ngx.say("This is our own content")
 -- to cause quit the whole request rather than the current phase handler
 ngx.exit(ngx.HTTP_OK)