如何修复 Node.js 投掷器； // 未处理的“错误”事件

Question

I'm learning Node.js, I just created a form, when I make post request my node js script will execute one terminal command to build using gradle. By default I use index.html to show form, Once my build is completed I want to show build.html page.

But I'm getting error,

My code:

const http = require('http');
const fs = require('fs');
const { spawn } = require("child_process");
var qs = require('querystring');
const server = http.createServer((req, res)=> {
    if (req.method == 'POST') {
        var body = '';
        console.log("Post received");
        
        req.on('data', function (data) {

            body += data;
            var post = qs.parse(body);


            // Too much POST data, kill the connection!
            // 1e6 === 1 * Math.pow(10, 6) === 1 * 1000000 ~~~ 1MB
            if (body.length > 1e6)
                req.connection.destroy();
        });

        req.on('end', function () {
            var post = qs.parse(body);
            // use post['blah'], etc.


            const ls = spawn("./gradlew", ["build"]);
            
            ls.stdout.on("data", data => {
               // console.log(`stdout: ${data}`);
            
            });
            
            ls.stderr.on("data", data => {
                console.log(`stderr: ${data}`);
            });
            
            ls.on('error', (error) => {
                console.log(`error: ${error.message}`);
            });
            
            ls.on("close", code => {
               //console.log(`child process exited with code ${code}`);
            console.log("Build success");
        const readStream = fs.createReadStream('./build.html');
res.writeHead(200, {'Content-type': 'text/html'});
readStream.pipe(res);


            });
            
                        
        });

        
    }

const readStream = fs.createReadStream('./index.html');
res.writeHead(200, {'Content-type': 'text/html'});
readStream.pipe(res);

});
server.listen('3000');

Error:

events.js:183
      throw er; // Unhandled 'error' event
      ^

Error: write after end
    at write_ (_http_outgoing.js:622:15)
    at ServerResponse.write (_http_outgoing.js:617:10)
    at ReadStream.ondata (_stream_readable.js:639:20)
    at emitOne (events.js:116:13)
    at ReadStream.emit (events.js:211:7)
    at addChunk (_stream_readable.js:263:12)
    at readableAddChunk (_stream_readable.js:250:11)
    at ReadStream.Readable.push (_stream_readable.js:208:10)
    at fs.read (fs.js:2051:12)
    at FSReqWrap.wrapper [as oncomplete] (fs.js:658:17)

How I can fix this error, How to show the build.html page once the build is successful.

Thanks in advance!

Answer 1

The error message string is being displayed on the error stack:

Error: write after end

readable.pipe calls end on the writable stream. In this case I believe you have a race condition between both of your file read streams.

/*****************************************************/
/*  First Stream                                     */
/*****************************************************/
console.log("Build success");
const readStream = fs.createReadStream('./build.html');
res.writeHead(200, {
    'Content-type': 'text/html'
});
readStream.pipe(res);

/*****************************************************/
/*  Second Stream                                    */
/*****************************************************/

const readStream = fs.createReadStream('./index.html');
res.writeHead(200, {'Content-type': 'text/html'});
readStream.pipe(res);

I believe you'd want the last stream only sent if it's not POST so you could add an else clause for any other type of request:

const http = require('http');
const fs = require('fs');
const {
    spawn
} = require("child_process");
var qs = require('querystring');
const server = http.createServer((req, res) => {
    if (req.method == 'POST') {
        var body = '';
        console.log("Post received");

        req.on('data', function(data) {

            body += data;
            var post = qs.parse(body);


            // Too much POST data, kill the connection!
            // 1e6 === 1 * Math.pow(10, 6) === 1 * 1000000 ~~~ 1MB
            if (body.length > 1e6)
                req.connection.destroy();
        });

        req.on('end', function() {
            var post = qs.parse(body);
            // use post['blah'], etc.


            const ls = spawn("./gradlew", ["build"]);

            ls.stdout.on("data", data => {
                // console.log(`stdout: ${data}`);

            });

            ls.stderr.on("data", data => {
                console.log(`stderr: ${data}`);
            });

            ls.on('error', (error) => {
                console.log(`error: ${error.message}`);
            });

            ls.on("close", code => {
                //console.log(`child process exited with code ${code}`);
                console.log("Build success");
                const readStream = fs.createReadStream('./build.html');
                res.writeHead(200, {
                    'Content-type': 'text/html'
                });
                readStream.pipe(res);


            });


        });
    } else {
        const readStream = fs.createReadStream('./index.html');
        res.writeHead(200, {
            'Content-type': 'text/html'
        });
        readStream.pipe(res);
    }
});
server.listen('3000')