Connect external Vercel Nextjs 13 Prisma application to Fly.io Postgres with ipv6

1

Hello,

I cannot figure out how to reach my fly.io postgres container from a Nextjs 13 (Prisma DB) app deployed on Vercel.

I have followed the guide on external connections and added an ipv6 address. The ipv4 address costs 2$/month, so I opted for ipv6.

My (auto-generated) fly.toml looks like this:


app = "<my postgres app name>"
primary_region = "<region>"

[env]
  FLY_SCALE_TO_ZERO = "1h"
  PRIMARY_REGION = "<region>"

[[mounts]]
  source = "pg_data"
  destination = "/data"

[[services]]
  protocol = "tcp"
  internal_port = 5432
  auto_start_machines = true

  [[services.ports]]
    port = 5432
    handlers = ["pg_tls"]
  [services.concurrency]
    type = "connections"
    hard_limit = 1000
    soft_limit = 1000

[[services]]
  protocol = "tcp"
  internal_port = 5433
  auto_start_machines = true

  [[services.ports]]
    port = 5433
    handlers = ["pg_tls"]
  [services.concurrency]
    type = "connections"
    hard_limit = 1000
    soft_limit = 1000

[checks]
  [checks.pg]
    port = 5500
    type = "http"
    interval = "15s"
    timeout = "10s"
    path = "/flycheck/pg"
  [checks.role]
    port = 5500
    type = "http"
    interval = "15s"
    timeout = "10s"
    path = "/flycheck/role"
  [checks.vm]
    port = 5500
    type = "http"
    interval = "15s"
    timeout = "10s"
    path = "/flycheck/vm"

[metrics]
  port = 9187
  path = "/metrics"

I have deployed this new configuration and it shows up in my dashboard.

I can connect on my local dev machine to the Postgres app without having to set up a proxy.

The connection string is something like this:

postgres://postgres:<my postgres password>@<my postgres app name>.fly.dev:5432/<my database name>?schema=public

However, using the exact same connection string (copy/paste) on Vercel leads to an error in my runtime logs:

Can't reach database server at `<my postgres app name>.fly.dev`:`5432`

Please make sure your database server is running at `<my postgres app name>.fly.dev`:`5432`.
    at zr.handleRequestError (/var/task/node_modules/.pnpm/@prisma+client@5.0.0_prisma@5.

Any help is appreciated.

2

I don’t have much experience with Vercel, but AFAIK they run their Serverless Functions on AWS Lambda, which doesn’t support ipv6 for outbound connections - AWS lambda function not able to resolve or connect to ipv6 only domain | AWS re:Post

3

If dedicated IP cost is an issue I would recommend trying shared IPv4: Announcement: Shared Anycast IPv4

4

Thanks for the suggestions.

Unfortunately, I now cannot connect externally to the database with a shared ip v4 via connection string or psql without a proxy.

Proxying works fine, the database seems healthy and running.

Does the shared ipv4 allow for connecting an external (Postgres) app, or would I need a dedicated ipv4 for that?

5

You can assign the shared ipv4 but connect using the .fly.dev domain on your connection string and our proxy should handle everything for you.

6

That doesn’t seem to work for me, but I appreciate your response.

$ psql "sslmode=require host=<my app name>.fly.dev> user=postgres"
> psql: error: connection to server at "<my-app-name>.fly.dev" (xx.xxx.xxx.xxx), port 5432 failed: server closed the connection unexpectedly
        This probably means the server terminated abnormally
        before or while processing the request.
7

I was looking for old threads to see if I could spot a solution and found this:

Sorry I might have misled you.

Another possibility I can think of is that you could setup wireguard on Vercel so you have access there to our internal DNS but I’m not sure if this is possible too.

8

Ah, I understand. Thank you @lubien.

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9

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