Use detect-port to check if 3000 is already used. #68

STRML · 2016-10-25T20:37:42Z

Based on create-react-app and specifically
facebook/create-react-app#101.

$ ./dist/bin/next-start
Something is already running at port 3000.
Would you like to run the app on port 3001 instead? [Y/n] y

Ready on http://localhost:3001
^C⏎

nkzawa · 2016-10-26T10:09:42Z

bin/next-start

-  console.log('> Ready on http://localhost:%d', argv.port)
-})
+
+run(srv, argv.port)


next start is expected to be used for production, thus I think just throwing an error can be better.
Or does this work even on like automated deployment too ?

I agree, let's just throw an error in next-start, will update. Throwing an error is still better than existing behavior, currently it will throw nothing and the previous owner of the port will simply be the only one bound.

nkzawa · 2016-10-26T10:11:55Z

gulpfile.js

@@ -26,7 +26,7 @@ gulp.task('compile', [
 ])

 gulp.task('compile-bin', () => {
-  return gulp.src('bin/*')
+  return gulp.src('bin/**/*.js')


I think bin/next and next/next-build etc wouldn't be compiled with this setting ?

Yes, this is true due to the extension - fixing

nkzawa · 2016-10-26T10:13:31Z

btw it seems great to support !

Based on create-react-app and specifically facebook/create-react-app#101 In production, will exit(1) if the port is in use.

STRML · 2016-10-26T14:42:36Z

Updated:

~/g/f/next.js (feature/detect-port) $ ./dist/bin/next-start
Error: Something is already running at port 3000. Exiting.
~/g/f/next.js (feature/detect-port) $ ./dist/bin/next-dev
Something is already running at port 3000.
Would you like to run the app on port 3001 instead? [Y/n] y

Ready on http://localhost:3001

Ready for review.

rauchg · 2016-10-26T16:09:11Z

Thank you! Awesome work. I'd like a bit of a simpler approach to this, however.

If you run next without specifying a port, and 3000 is taken, we warn (> Note: default port already in use! Picking an available port), and pick a free one.

Prompting and all that seems a bit much?

STRML · 2016-10-26T16:52:42Z

I don't think it's a bit much - you may have a good reason for not picking another port and you want to be prompted. Perhaps you could miss the prompt outright if it just started up, especially if your application prints a lot of logs on startup.

In any case, this is convention from create-react-app and I believe it really works well there.

mmmeff · 2016-10-26T18:31:17Z

Agreed with @STRML - quietly deviating from default behavior is an anti-pattern - best to be verbose with a bit much in that case.

iamstarkov · 2016-10-26T20:52:12Z

you may have a good reason for not picking another port and you want to be prompted

then you better specify exact port.

iamstarkov · 2016-10-26T20:53:29Z

So i agree with @rauchg if no port is specified, app should run on whatever port is available

Though, if port is specified, then its better to process.exit(-1), as @STRML noted, that if you need specified port, and its not available, you dont want to run app on other ports

rauchg · 2016-10-29T10:49:41Z

Thanks for continuing the discussion!

If you run next, you're not specifying a port. You're telling next to use default behavior.
In our case, the default behavior would not be 3000, it'd be "a friendly port we can find". In fact, we could try 3000, 8080, 3000+i…

you may have a good reason for not picking another port and you want to be prompted.

What would be a good reason that you're likely to run into? And that you would not be better off by running next -p {port you really need}

I think adding so much logic to ask the user a question that they likely will answer "yes" during development is not worth it.

Important to keep in mind: we're using this for next, not for production-ready next start. Therefore, it's not harmful to make more assumptions here.

daytonna · 2016-10-29T10:53:22Z

Detect port authority new to routing sorry :)
On Oct 29, 2016 6:49 AM, "Guillermo Rauch" [email protected] wrote:

Thanks for continuing the discussion!

If you run next, you're not specifying a port. You're telling next to use
default behavior.
In our case, the default behavior would not be 3000, it'd be "a friendly
port we can find". In fact, we could try 3000, 8080, 3000+i…

you may have a good reason for not picking another port and you want to be
prompted.

What would be a good reason that you're likely to run into? And that you
would not be better off by running next -p {port you really need}

I think adding 2 files to ask the user a question that they likely will
answer "yes" during development is not worth it.

Important to keep in mind: we're using this for next, not for
production-ready next start. Therefore, it's not harmful to make more
assumptions here.

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mbilokonsky · 2016-10-31T16:44:05Z

Trick with automagic port selection is, what if you have a session running in a different terminal tab? You make your changes, you start again, you go refresh your browser thinking you're on port 3000, but your latest version quietly started on port 3001.

How long do you spend trying to figure out why you're not seeing your latest changes reflected?

I like prompting you to accept port 3001 because it will also force you to think "Oh, crap, what's running on 3000? Oh I left this running..." etc.

We've all been burned by that, right?

STRML · 2016-11-07T16:17:44Z

I think adding so much logic to ask the user a question that they likely will answer "yes" during development is not worth it.

It's a few lines - and it's very nice to be prompted as a way of saying "something out of the ordinary is happening here". Because the expectation, if you run it more than once, is that it will open on port 3000. And developers who use it will build that expectation that if you don't start it with -p, it will start on 3000. So if we have reason not to start on 3000, thus breaking expectations, a prompt (as opposed to just another log line) is a very good way to make this clear.

arunoda · 2016-11-14T10:37:28Z

Every line of code we put in is a liability

I agree with both @rauchg and @mbilokonsky.
What if we say this:

Port 3000 is already in use.
Use `npm run dev -- -p <some other port>`.

Or something similar.

rauchg · 2016-12-17T03:37:00Z

@arunoda that sounds great to me

hegelstad · 2017-04-10T10:29:43Z

Why do we need double dashes before -p?

Spent 15 minutes figuring this out. It's not easy to find in the docs either. Also, there is no error if you are running a docker exposed to port 3000.

STRML · 2017-04-10T16:31:53Z

The double dashes are not a next thing, they are how npm run (and many other utilities) mark the end of the parameter list. This indicates that you are sending the -p to the script executed by npm run dev, not to npm run itself.

This fixes vercel#68 and closes vercel#69

nkzawa reviewed Oct 26, 2016

View reviewed changes

Use detect-port to check if desired is already used.

c0a443e

Based on create-react-app and specifically facebook/create-react-app#101 In production, will exit(1) if the port is in use.

STRML force-pushed the feature/detect-port branch from e23b2f2 to c0a443e Compare October 26, 2016 14:42

arunoda mentioned this pull request Dec 7, 2016

Automatically select port when starting #358

Closed

rauchg closed this Dec 17, 2016

arunoda mentioned this pull request Jan 30, 2017

Port already being used #927

Closed

nkzawa mentioned this pull request Feb 10, 2017

Fall back to random open port if specified/default one is in use #1066

Closed

lock bot locked as resolved and limited conversation to collaborators Jan 18, 2019

ijjk pushed a commit to ijjk/next.js that referenced this pull request Apr 13, 2019

Properly link small headings (vercel#74)

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This fixes vercel#68 and closes vercel#69

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Use detect-port to check if 3000 is already used. #68

Use detect-port to check if 3000 is already used. #68

STRML commented Oct 25, 2016

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Use detect-port to check if 3000 is already used. #68

Use detect-port to check if 3000 is already used. #68

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