Warn user when something else is already running on port 3000

[TimonVS]

Feature Request

Is your feature request related to a problem? Please describe.

When running Probot locally and you've already got something else running on port 3000 (Create React App and many other tools use 3000 by default) Probot will log "Not Found" errors when a webhook event is received.

Describe the solution you'd like

It'd be nice if Probot would detect if a something is already running on port 3000. Create React App does this as well:

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Teachability, Documentation, Adoption, Migration Strategy
If you can, explain how users will be able to use this and possibly write out a version the docs.
Maybe a screenshot or design?

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[NikhilM98]

I was planning to work on this issue. It'll be my second issue on Probot after #778 so I'm open to suggestions. This would be a nice feature to the Probot.

The file probot/src/index.ts contains the Probot class. It creates a new express server on the specified port from the options. I was planning to catch errors on this.server.listen and if EADDRINUSE error is present then we'll tell the user that "maybe the port is already used. Would you like to use another port?" If the user inputs YES then we'll increment the port number by 1 and call this.server.listen again and then we'll start the webhook proxy.

I'm looking forward to feedback.

[JasonEtco]

@NikhilM98 excited to see you contribute again!

I think your proposed implementation would be more than is necessary. That flow of incrementing the port would add a good amount of code; in my experience, when I see an EADDRINUSE error its usually because I forgot to close a server, so I just go and do that.

Instead, how about catching that error and printing a message like:

Port {{ port }} is already in use. You can define the PORT environment variable to use a different port.

[NikhilM98]

Thanks, @JasonEtco for the feedback.

I've made a PR following the changes you requested.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.