Shulou(Shulou.com)06/02 Report--

This article is about how to deal with concurrency on CVM. The editor thinks it is very practical, so I share it with you. I hope you can get something after reading this article. Let's take a look at it with the editor.

The purpose of designing a concurrency strategy for CVM is to allow IO operations and CPU computing to overlap as much as possible. On the one hand, you need to keep CPU waiting for IO without being idle, and on the other hand, let CPU spend as little time as possible on IO scheduling.

Concurrency strategy of general CVM

(1) one process handles one connection, and non-blocking IO

In this way, when multiple concurrent requests arrive at the same time, the CVM must prepare multiple processes to process the requests. Typical examples of this strategy are Apache's fork and prefork modes. For sites that do not have a high number of concurrency and rely on other features of Apache, it is possible to choose Apache.

(2) one thread handles one connection, non-blocking IO

This approach allows multiple connections to be processed by multiple threads in a process, and one thread handles one connection. Apache's worker pattern is a typical example of this, allowing it to support more concurrent connections. However, the overall performance of this mode is not as good as that of prefork, so worker mode is generally not chosen.

(3) one process handles multiple connections, and non-blocking IO

The prerequisite for application is the application of multi-channel IO readiness notification. In this case, a process that handles multiple connections is called a worker process or a service process. The number of worker can be configured, such as worker_processes 4 in Nginx.

(4) one thread handles multiple connections, asynchronous IO

Even with high-performance multiplex IO ready notifications, the wait for disk IO is inevitable. A more efficient approach is to use asynchronous IO for disk files, and few Web servers currently rent to support this asynchronous IO in a real sense.

This is how the CVM handles concurrency. The editor believes that there are some knowledge points that we may see or use in our daily work. I hope you can learn more from this article. For more details, please follow the industry information channel.

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