nginx的 say和print的异步输出

Question

server {
        listen    80;

        location /test {
            content_by_lua_block {
                ngx.say("hello")
                ngx.sleep(3)
                ngx.say("the world")
            }
        }

        location /test2 {
            content_by_lua_block {
                ngx.say("hello")
                ngx.flush() -- 显式的向客户端刷新响应输出
                ngx.sleep(3)
                ngx.say("the world")
            }
        }
    }

想知道，对于/test来说，hello和 the world 一起输出，这不就是同步了嘛，哪里叫异步呀？

Answer 1

ngxxprint:

This is an asynchronous call and will return immediately without waiting for all the data to be written into the system send buffer.

异步是指函数不会等写入完成再返回。