What can swoole coroutine do?

In swoole, coroutines can be used for high-concurrency services. The fault tolerance rate of services using coroutine mode will be greatly increased. Failure of certain interfaces will not cause the service to crash. It can also be used for instant messaging and chatting. , which can ensure that communication is completely non-blocking and each message can be processed immediately.

The operating environment of this tutorial: Windows10 system, Swoole4 version, DELL G3 computer

What can the swoole coroutine do

Applicable scenarios of coroutines

Highly concurrent services, such as flash sales systems, high-performance API interfaces, and RPC servers, use coroutine mode, the fault tolerance rate of services will be greatly increased, and certain interfaces may In the event of a failure, the entire service will not collapse.

Crawler can achieve very huge concurrency capabilities, and can efficiently utilize bandwidth even in a very slow network environment.

Instant messaging services, such as IM chat, game server, Internet of Things, message server, etc., can ensure that message communication is completely non-blocking and each message packet can be processed instantly.

What is a coroutine?

Coroutine (Coroutine) is also called a user-mode thread, which switches through collaboration rather than preemption. Compared with processes or threads, all operations of coroutines can be completed in user mode, and creation and switching costs are lower. A coroutine is a complement to a process, or a complementary relationship.

To understand what a "user-mode thread" is, you must first understand what a "kernel-mode thread" is. Kernel state threads are scheduled by the operating system. When switching thread contexts, you must first save the context of the previous thread, and then execute the next thread. When the conditions are met, switch back to the previous thread and restore the context. The same is true for coroutines, except that user-mode threads are not scheduled by the operating system, but by programmers, which are so-called user-mode threads.

The difference between coroutines and threads

Swoole's coroutine is single-threaded in the underlying implementation, so only one coroutine is working at the same time, and the execution of the coroutine is serial. This is different from threads. Multiple threads will be scheduled by the operating system to multiple CPUs for parallel execution.

When one coroutine is running, other coroutines will stop working. The current coroutine will hang when performing blocking IO operations, and the underlying scheduler will enter the event loop. When there is an IO completion event, the underlying scheduler resumes the execution of the coroutine corresponding to the event.

The utilization of CPU multi-core still relies on the multi-process mechanism of the Swoole engine.

Recommended learning: swoole tutorial

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