Libuv asynchronous task logic and UV_ queue_ work()

Preface

libuv No, asio Of post function , But we can uv_async_init+uv_async_send simulation ,uv_async_send Parameters can be transferred by async.data. Because some tasks are time-consuming （ Such as file reading and writing , Or connection mysql）, If you add it directly to eventloop in , It will affect eventloop Throughput , therefore libuv Provides uv_queue_work To solve this situation .

libuv Asynchronous task logic

This part is actually uv_loop_run Extension of , Instead of code by code analysis, go directly to the flow chart .

uv_queue_work（loop,callback, done）

libuv Provides thread pool . In order to solve the problem that some asynchronous tasks take too long, it will affect eventloop Throughput of , We can divide this task into two parts ：callback Time consuming logic ,done For the end of execution callback The follow-up logic of .callback Give it to the thread pool to complete , Add... As soon as you're done done To eventloop in , Then wake up eventloop, call uv_work_done function , call done function .

uv_queue_work Of work req Detailed flow chart for adding and callback triggers

Here I can feel more req and handle The difference between ,handle It always exists after initialization loop in , We need to call close From the loop Remove , but req You don't need to , After adding to the thread pool work queue , After one execution , It will be removed from the work queue ,done Part of the same （ from loop Of wq Remove ）.