Use proxy_read_timeout to simulate task queue in ngx_openresty

ngx_queue.conf

server {
    listen 9999;

    resolver 8.8.8.8;

    location = /add-q {
        content_by_lua "
    ngx.location.capture('/i-add-q', {
        args = {
            uri = '/run-q'
        }
    })
    ngx.log(ngx.WARN, 'task created')
    ngx.say(':)')
        ";
    }
    location = /i-add-q {
        proxy_read_timeout 20ms;
        set_unescape_uri $_uri $arg_uri;
        proxy_pass http://127.0.0.1:$server_port$_uri;
    }

    location = /run-q {
        content_by_lua "
    -- slow actions
    local res = ngx.location.capture('/fetch-any', {
        args = {
            srv = 'www.baidu.com',
            host = 'www.baidu.com',
            uri = '/',
        }
    })
    ngx.log(ngx.WARN, 'got resp', res.body)
        ";
    }
    location = /fetch-any {
        set_unescape_uri $_srv $arg_srv;
        set_unescape_uri $_host $arg_host;
        set_if_empty $_host localhost;
        set_unescape_uri $_uri $arg_uri;
        proxy_set_header Host $_host;
        proxy_pass http://$_srv$_uri;
    }

}