UnhandledPromiseRejectionWarning when deploying custom server to now

[jessehattabaugh]

In order to use a hostname other than localhost I'm creating a custom server as @arunoda advised in #1010.

const { createServer } = require('http');
const { parse } = require('url');
const next = require('next');

const port = process.env.PORT || 3000;
const hostname = process.env.IP || 'localhost';
const app = next({ dev: process.env.NODE_ENV !== 'production' });
const handle = app.getRequestHandler();

app.prepare().then(() => {
  createServer((req, res) => {
  	const parsedUrl = parse(req.url, true);
  	handle(req, res, parsedUrl);
  })
  .listen(port, hostname, (err) => {
    if (err) throw err;
    console.log(`> Ready on http://${ hostname }:${ port }`);
  });
});

My package.json scripts are as follows

"scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "deploy": "now",
    "build": "next build",
    "start": "node server"
  },

Running $ npm start works as expected, but when I deploy to now using $ npm run deploy I get the following output

npm install
⧗ Installing:
 ‣ next@^2.0.0-beta.24
 ‣ now@^4.2.2
✓ Installed 646 modules [18s]
npm run build

> studynew@0.0.0 build /home/nowuser/src
> next build
npm start

> studynew@0.0.0 start /home/nowuser/src
> node server
(node:233) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): Error: EACCES: permission denied, rmdir '/home/nowuser/src/.next'
(node:233) DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

may be related to #452 or #300

[jessehattabaugh]

I tried adding a .catch((err) => console.error(err)) to the promise returned by prepare() and now the error I get when deploying is

> ▲ npm start
> > studynew@0.0.0 start /home/nowuser/src
> > node server
> { Error: EACCES: permission denied, rmdir '/home/nowuser/src/.next'
>   errno: -13,
>   code: 'EACCES',
>   syscall: 'rmdir',
>   path: '/home/nowuser/src/.next' }

[bryanrsmith]

const app = next({ dev: process.env.NODE_ENV !== 'production' });

I think you'll need to use "start": "NODE_ENV=production node server" to switch next out of dev mode.

[jessehattabaugh]

Huh, I would've expected Now.js to set NODE_ENV to 'production' the way Heroku does.

I checked for NOW and it works now!

const app = next({ dev: process.env.NODE_ENV !== 'production' && !process.env.NOW });

[rauchg]

@jessehattabaugh we didn't want to be surprising. After all, you could launch processes to simulate development, you could run builds, etc. What do you think?

[jessehattabaugh]

I think it's more intuitive to do NODE_ENV=development when I'm trying to simulate development in my production environment than to have to explicitly declare NODE_ENV=production which seems like it should be the default. If I'm running a build on production I probably want it to be a production build. I sometimes use NODE_ENV to trigger things like minification and watchers in my builds. I feel like the command to start my server should be the same on production and development; $ npm start without having to explicitly set NODE_ENV before running it.

[rauchg]

Sounds good. Thanks a lot for your feedback

[timneutkens]

This is only the case when running a custom server. next build and next start both set production as process.env.NODE_ENV if it is not defined by the user.

[bryanrsmith]

FWIW, this exact thing happened to me the first time I deployed a custom server. I also expected now to set NODE_ENV=production.

It makes sense why it's set up this way; I just had to make the mistake once to learn it. I think this specific case could be improved a lot if Next.js could catch this error and log a helpful message. Maybe it could even look at process.env.NOW and tell the user they need to set NODE_ENV.

[headwinds]

agree with @bryanrsmith if the error could also point to this thread and/or a doc about this issue.

I encountered it after following the custom express example but not as closely as I should have. I missed the yarn dev part and began with yarn start instead which most apps begin with for local dev. Then couldn't figure why I wasn't getting HMR and when I went to deploy it was still in dev mode but this thread sorted everything out.