Tokio 無(wú)疑是 Rust 世界中最優(yōu)秀的異步Runtime實(shí)現(xiàn)。非阻塞的特性帶來(lái)了優(yōu)異的性能，但是在實(shí)際的開(kāi)發(fā)中我們往往需要在某些情況下阻塞任務(wù)來(lái)實(shí)現(xiàn)某些功能。

我們看看下面的例子

fn main(){


        let max_task = 1;


        let rt = runtime::new_multi_thread()


            .worker_threads(max_task)


            


            .build()


            .unwrap();     


        rt.block_on(async {


            println!("tokio_multi_thread ");


            for i in 0..100 {


                println!("run {}", i);     


                tokio::spawn(async move {


                    println!("spawn {}", i);


                    thread::from_secs(2));


                });


            }


        });


    }

tokio_multi_thread


run 0


run 1


run 2


.......


run 16


spawn 0


run 17


......


run 99


spawn 1


spawn 2


......


spawn 29


......


spawn 58


spawn 59

我們看看下面的代碼。

fn main(){


        let max_task = 2;


        let rt = runtime::new_multi_thread()


            .worker_threads(max_task)


            .enable_time()


            .build()


            .unwrap();     


        let mut set = JoinSet::new();


        rt.block_on(async {


            for i in 0..100 {


                println!("run {}", i);


                while set.len() >= max_task {


                    set.join_next().await;


                }


                set.spawn(async move {


                    sleep().await;


                    println!("spawn {}", i);


                });


            }


            while set.len() > 0 {


                set.join_next().await;


            }


        });


    }

輸出大概長(zhǎng)這樣

running 1 test


tokio_multi_thread


run 0


run 1


spawn 0


run 2


spawn 1


......


run 31


spawn 30


run 32


spawn 31


run 33


......


run 96


spawn 95


run 97


spawn 96


run 98


spawn 97


run 99


spawn 98


spawn 99

審核編輯 ：李倩