readFile()和readFileSync()之间的区别 [英] Difference between readFile() and readFileSync()

问题描述

以下代码将index.html的内容(它仅包含文本hello world)输出到浏览器.但是，当我用readFileSync()替换readFile()时，请求超时.

The following code outputs the content of the index.html (it just contains the text hello world) to the browser. However, when I replace readFile() with readFileSync(), the request times out.

我想念什么?是否需要其他类型的缓冲区?我正在使用节点0.61并表示2.4.

What am I missing? Is a different kind of buffer required? I am using node 0.61 and express 2.4.

var express = require('express');
var fs = require('fs');

var app = express.createServer(express.logger());

app.get('/', function(request, response) {
    fs.readFile('index.html', function(err, data){
        response.send(data.toString());
    });
});

var port = process.env.PORT || 5000;
app.listen(port, function() {
  console.log("Listening on " + port);
});

推荐答案

fs.readFile 进行回叫，如您所显示的那样调用response.send-很好.如果您只是将其替换为 fs.readFileSync ，则需要注意一个回调，这样您的调用response.send的回调将永远不会被调用，因此响应将永远不会结束并且会超时.

fs.readFile takes a call back which calls response.send as you have shown - good. If you simply replace that with fs.readFileSync, you need to be aware it does not take a callback so your callback which calls response.send will never get called and therefore the response will never end and it will timeout.

如果您不只是将readFile替换为readFileSync，则需要显示readFileSync代码.

You need to show your readFileSync code if you're not simply replacing readFile with readFileSync.

也请注意，您应该从不永远不要在节点express/webserver中调用readFileSync，因为它会在执行I/O时阻塞单线程循环.您希望节点循环能够处理其他请求，直到I/O完成并且您的回调处理代码可以运行为止.

Also, just so you're aware, you should never call readFileSync in a node express/webserver since it will tie up the single thread loop while I/O is performed. You want the node loop to process other requests until the I/O completes and your callback handling code can run.

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