NGX_EHOSTDOWN    1254 src/core/ngx_connection.c         || err == NGX_EHOSTDOWN
NGX_EHOSTDOWN     140 src/event/ngx_event_connect.c                 || err == NGX_EHOSTDOWN
NGX_EHOSTDOWN    1883 src/event/ngx_event_openssl.c             || err == NGX_EHOSTDOWN