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This article will explain to you in detail what is blocking Blocking, the content of the article is of high quality, so the editor will share it for you as a reference. I hope you will have a certain understanding of the relevant knowledge after reading this article.

Node.js blocking (Blocking) and nonblocking (Non-Blocking). I'll mention EventLoop and libuv, but not knowing them won't affect reading. Readers only need to have a basic knowledge of JavaScript and understand the callback function (callbackpattern) of Node.js. There are many references to iCompo, which mainly refers to the use of libuv to interact with the system's disk and network.

What is blocking (Blocking)

Blocking means that part of the Node.js code needs to wait until some non-Node.js code has been executed before it can continue to execute. This is because EventLoop cannot continue execution when blocking occurs.

For Node.js, blocking cannot be called when code performance is poor due to CPU-intensive operations. It is called blocking when you need to wait for non-Node.js code to execute. Blocking is caused by libuv-dependent synchronization methods (ending in Sync) in Node.js, which is the most common case. Of course, some native Node.js methods that do not depend on libuv can also cause blocking.

All Node.js-related methods that are available asynchronously are non-blocking and can specify callback functions such as fs.readFile. Some of these methods also have corresponding blocking versions, whose function names end with Sync, such as fs.readFileSync.

Blocking code example

Blocking methods are executed synchronously, while non-blocking methods are executed asynchronously.

Taking reading a file as an example, here is the code that executes synchronously:

Constfs=require ('fs')

Constdata=fs.readFileSync ('/ file.md'); / / the code blocks and does not execute the rest of the code until the file is read

Console.log ("Hello,Fundebug!"); / / the file will not be printed until it has been read.

The corresponding asynchronous code is as follows:

Constfs=require ('fs')

Fs.readFile ('/ file.md', (err,data) = > {

If (err) throwerr

}); / / the code will not be blocked by reading the file and will continue to execute the following code

Console.log ("Hello,Fundebug!"); / / the file will be printed before it is finished.

The first sample code looks much simpler, but its disadvantage is that it blocks code execution, and the rest of the code needs to wait until the entire file has been read before it can continue.

In synchronization code, if there is an error reading the file, the error needs to be handled using try...catch, otherwise the process will crash. For asynchronous code, it is up to the developer whether or not to handle callback function errors.

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