Setting up rails as private service to a nextjs app (ECONNRESET error)

[jyoo]

Hello, I have created a new rails app and a nextjs app. I want the rails app to function as a private service that can be reached by the nextjs app but not by the public internet.

I have been trying to follow the official documentation (Private Networking · Fly Docs) and some forum posts ([1], [2]). First, I tried to bind my rails app to [::] with the following.

[processes]
  app = './bin/rails server -b [::] -p 3000'

From some forum posts ([3]) this seemed like it would expose the service to the public, but I just wanted to get the private ipv6 networking to work first. But when I tried to call the service, it did not work.

So then I tried giving my rails app a dedicated ipv6 address and have it bind to that

[processes]
  app = './bin/rails server -b [fdaa:6:xxxxxxxx] -p 3000'

With this, I was still able to get the address from dns lookups

await dns.promises.resolve6('appname.flycast') // => [ 'fdaa:6:xxxxxxxx' ]

But when I tried to call the address, I kept getting ECONNRESET errors

await fetch('http://appname.flycast:3000/_status') // => ECONNRESET error
await fetch('http://[fdaa:6:xxxxxxxx]:3000/_status') // => ECONNRESET error

What would I be doing wrong?

[mayailurus]

@jyoo

What would I be doing wrong?

Hi… My guess is force_https, which doesn’t play nicely with Flycast…

Perhaps you could post your full fly.toml? There might be multiple things going wrong simultaneously.

And also the output of fly ips list -a rails-app-name, just to double-check.

---

In general, you can’t bind to the .flycast address directly. The Fly proxy is what sits there. With recent Rails, I think -b can be omitted completely, .

[jyoo]

Hi @mayailurus , thanks for your reply, currently my fly.toml looks like below. It’s pretty much what I got from fly launch with just the app= and force_https= edited.

# fly.toml app configuration file generated for yolets-be on 2024-02-13T13:23:04-05:00
#
# See https://fly.io/docs/reference/configuration/ for information about how to use this file.
#

app = 'yolets-be'
primary_region = 'yyz'
console_command = '/rails/bin/rails console'

[build]

[deploy]
  release_command = './bin/rails db:prepare'

[processes]
  app = './bin/rails server -b [fdaa:6:67aa:0:1::3] -p 3000'
  solidq = 'bundle exec rake solid_queue:start'

[http_service]
  internal_port = 3000
  force_https = false
  auto_stop_machines = true
  auto_start_machines = true
  min_machines_running = 0
  processes = ['app']

[checks]
  [checks.status]
    port = 3000
    type = 'http'
    interval = '10s'
    timeout = '2s'
    grace_period = '5s'
    method = 'GET'
    path = '/up'
    protocol = 'http'
    tls_skip_verify = false

    [checks.status.headers]
      X-Forwarded-Proto = 'https'

[[vm]]
  cpu_kind = 'shared'
  cpus = 1
  memory_mb = 1024
  processes = ['app', 'solidq']

[[statics]]
  guest_path = '/rails/public'
  url_prefix = '/'

The output of fly ips list is

VERSION IP                      TYPE                    REGION  CREATED AT        
v6      2a09:8280:1::2a:98e5:0  public (dedicated)      global  Feb 13 2024 18:25
v6      fdaa:6:67aa:0:1::3      private                 global  Feb 17 2024 21:47
v4      66.241.124.247          public (shared)                 Jan 1 0001 00:00

[rubys]

I’m not sure yet what you are trying to do, but I will make a few observations. But first, I agree that ECONNRESET is generally ssl errors.

• If you are running your Rails app in production, and you should, check config/environments/production.rb for config.force_ssl = true. You don’t want that.
• [http_service] is for connecting your app to the internet. Since you don’t want your Rails app accessible outside of the private network, delete this section.
• Perhaps it might be easier to run both services on one machine, but on different ports? See: Running Multiple Processes Inside A Fly.io App · Fly Docs

[jyoo]

I was able to get it to work by

• Removing config.force_ssl = true in production.rb
• Removing [http_service] and not adding [[service]] either (as found in the docs)
• Updating my app process command to app = './bin/rails server -b [::] -p 8080'

Thanks!