Ch5, Lab 1 - validate running before server ready
Hi all,
I'm attempting to complete the lab for ch-5 ("Implement a RESTful JSON GET").
I've create the server using express but when I run node validate
I get an error stating " Unable to connect to server on port: ....".
It looks like the validate() checks are running before the express server is actually ready. I added a delay to validate.js to wait 1000ms before the validate() function runs just to test it out. When I do this, the code passes successfully so it looks like I've missed something out on my code - but I'm not sure what? Can anyone point me in the right direction?
I've set my npm start
correctly. Running in VS Code, Windows 10.
My Code:-
const express = require('express'); const model = require('./model'); const app = express(); app.get('/boat/:id', (req, res) => { model.boat.read(req.params.id, (err, data) => { if (err) { if (err.code == 'E_NOT_FOUND') { res.sendStatus(404); } else { res.sendStatus(500); } } else { res.send(data); } }) }); app.use(function (req,res,next){ res.status(404).send('Unable to find the requested resource!'); }); app.listen(process.env.PORT, () => { console.log(`Listening on ${process.env.PORT}`) });
Thanks!
Comments
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One extra note, this worked fine for me using Fastify - it's just the Express version I can't seem to get working without introducing a delay before validate()
0 -
the function should be async, then you wait until finished or maybe return a promise.
const data = require('../../data') router.get('/', async (req, res) => { const randomString = await data(); res.send(randomString) })
0 -
@caphsob I've checked your code against validate.js and it seems to work just fine. This may be related to your host machine and there's perhaps a race condition. I'm going to update the start function in validate.js to:
async function start () { const server = net.createServer().listen() await once(server, 'listening') const { port } = server.address() server.close() await once(server, 'close') await writeFile(join(__dirname, 'model.js'), testingModel()) const sp = spawn(process.platform === 'win32' ? 'npm.cmd' : 'npm', ['start'], { env: { ...process.env, PORT: port }, stdio: ['ignore', 'ignore', 'inherit'] }) const [ err ] = await Promise.race([once(sp, 'spawn'), once(sp, 'error')]) try { if (err) throw err await validate({ port }) } catch (err) { if (err.code === 'ERR_ASSERTION') { console.log('⛔️ ' + err.message) process.exit(1) } throw err } finally { await writeFile(join(__dirname, 'model.js'), model()) try { sp.kill() } catch {} } }
This being the key line:
const [ err ] = await Promise.race([once(sp, 'spawn'), once(sp, 'error')])
The
spawn
event was only added fairly recently, so this will be part of our major update to Node v16 (but you can try this out with Node 14/Node 16 and see if it works).@jhonny111s avoid recommending async functions be used with Express, the training material goes into detail as to why this is a bad idea.
0 -
same thing happened to me using windows 10, fastify, and the latest validate.js.
the server child process took a smidge over two seconds to start listening for requests so the validation code (the validate function in validate.js) throws an AssertionError with message 'Unable to connect to server on port:...'.
in validate.js, in function validate, changing the if block condition to
retries > 6
should avoid this problem on most machines i would guess1 -
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