Error "write after end" being thrown when calling the /username route.

Question

I am getting the above error when trying to get a valid or invalid user name. I should mention that the page renders perfectly but when I return to the terminal, the server has crashed. Below is a sample trace and the related code.

Trace

events.js:182
      throw er; // Unhandled 'error' event
      ^

Error: write after end
    at write_ (_http_outgoing.js:620:15)
    at ServerResponse.write (_http_outgoing.js:615:10)
    at Object.view (/Users/amberdiehl/js_development/TreehouseNodeServer/renderer.js:32:11)
    at Profile.<anonymous> (/Users/amberdiehl/js_development/TreehouseNodeServer/router.js:28:13)
    at emitOne (events.js:115:13)
    at Profile.emit (events.js:210:7)
    at IncomingMessage.<anonymous> (/Users/amberdiehl/js_development/TreehouseNodeServer/profile.js:38:36)
    at emitNone (events.js:110:20)
    at IncomingMessage.emit (events.js:207:7)
    at endReadableNT (_stream_readable.js:1057:12)

app.js

const http = require('http');
var router = require('./router');

const hostname = '127.0.0.1';
const port = 8000;

//1. Create web server
const server = http.createServer((request, response) => {
    router.home(request, response);
    router.user(request, response);
});

server.listen(port, hostname, () => {
  console.log(`Server running at http://${hostname}:${port}/`);
});

router.js

var Profile = require("./profile.js");
var renderer = require("./renderer.js");

var commonHeader = {"Content-Type": "text/html"} // was {"Content-Type": "text/plain"}

function homeRoute(request, response){
    if (request.url === '/') {
        response.writeHead(200, commonHeader);
        renderer.view('search', {}, response);
    }
}

function userRoute(request, response){
    var userName = request.url.replace('/', '');
    if (userName.length > 0) {

        var values = {};

        var studentProfile = new Profile(userName);
        studentProfile.on("end", function(profileJSON) {

            values["avatarUrl"] = profileJSON.gravatar_url;
            values["username"] = profileJSON.profile_name;
            values["badges"] = profileJSON.badges.length;
            values["javaScriptPoints"] = profileJSON.points.JavaScript;

            response.writeHead(200, commonHeader);
            renderer.view('profile', values, response); 
        });

        studentProfile.on("error", function(error){

            values["errorMessage"] = error.message;
            response.writeHead(200, commonHeader);
            renderer.view('search', values, response);
        });

    }
}

module.exports.home = homeRoute;
module.exports.user = userRoute;

renderer.js

var fs = require('fs');

function mergeValues(values, content){

    for (var key in values) {
        content = content.replace("{{" + key + "}}", values[key]);
    }
    return content;
}

function view(templateName, values, response) {

    // If error, render error template first and pass to content
    if ('errorMessage' in values) {
        var errorTemplate = fs.readFileSync('./templates/error.html', 'utf8');
        errorTemplate = mergeValues(values, errorTemplate);
        values["errorTemplate"] = errorTemplate;
    } else {
        values["errorTemplate"] = '';
    }

    // Get content template and merge data values
    var contentTemplate = fs.readFileSync('./templates/' + templateName + '.html', 'utf8');
    contentTemplate = mergeValues(values, contentTemplate);

    // Get base template and merge content template
    var baseTemplate = fs.readFileSync('./templates/base.html', 'utf8');
    values["body"] = contentTemplate;
    baseTemplate = mergeValues(values, baseTemplate);

    // Write response
    response.write(baseTemplate);
    response.end();
}

module.exports.view = view;

Regarding the templates (the html files located in the "views" folder that I placed in a "templates" folder), I have created a base.html which is similar to but not the same as the 'header.html' in the course, the key difference being that it includes a {{body}} variable and the closing html tag.

In turn, either profile.html or search.html are being rendered into the {{body}} variable. And finally, the search.html has a {{errorTemplate}} tag that is replaced with the error div (and message) if the user profile is not found.

I can share the contents of these templates, of course, if that would be of value but since they're rendering did not include them.

Thanks in advance to any help!

Answer 1 · 2018-04-11T00:22:14Z

April 11, 2018 12:22am

Okay, I think I solved this (though it's a hack). Hopefully, this may save someone else a lot of time.

I moved the logging of the request.url to the server before the routes were executed and saw that /favicon.ico was being executed (though not all the time, from what I can tell). That route would be executed immediately after a legit user profile request and was causing the failure.

I added this to the app.js and all is working:

    if (request.url === '/') {
        router.home(request, response);
    } else if (request.url != 'favicon.ico') {
        router.user(request, response);
    }

There must be a better way; implementing something similar to Django's url.py and using regular expressions to invoke views. :)

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Amber Diehl

Amber Diehl

Error "write after end" being thrown when calling the /username route.

Amber Diehl

Amber Diehl

1 Answer

Amber Diehl

Amber Diehl

Gabbie Metheny

Gabbie Metheny