Bye Heroku, hey Fly.io

Migrate datastore for this blog’s comment system

I still remember the first time I deployed a database backed website with a single command, it completely blows my mind and the tool made it possible was Heroku. Nowadays when talking about containerization, Docker/k8s gets mentioned a lot, but the real pioneer in that space (PAAS) is Heroku, at least to me. It offloads the burden of provisioning (e.g. bins/libs installation), scaling (e.g. load balancing), dealing with security (e.g. tls/ssl termination) and a lot other chores from programmers, so that they only need to focus on building the app. However, Heroku recently (11/28) cancelled its free plan for all customers. As a result, I did a bit research to look for an alternative and came across another great tool - fly.io.

Background

One practical reason I’m looking for a Heroku alternative is that I’m using its Heroku Postgres service. The comment system of this blog is powered by https://github.com/djyde/cusdis thanks to Randy (the creator), self hosted by Vercel (compute) and Heroku Postgres (storage) with a simple comment form widget (iframe) at the bottom of this page. Since it's mostly a quiet blog, the free-tier plan of both services is more than enough for comments.

Migration Guide

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Smart move, isn't it?

Migration Steps

Breaking down into 2 parts, 1) Migrating the data to Fly Postgres 2) Exposing to external connections (i.e. DB_URL for above Vercel app to connect).

Migrating the data to Fly Postgres

Provision database app

```bash
fly pg create -n "cusdis-db"
```
```bash
fly secrets set -a cusdis-db DATABASE_URL=postgres://postgres:<password>@cusdis-db.internal:5432
```

Data transfer

```bash
fly secrets set -a cusdis-db HEROKU_DATABASE_URL=$(heroku config:get -a cusdis2 DATABASE_URL)
```
```bash
fly ssh console -a cusdis-db
createdb --maintenance-db $DATABASE_URL cusdis
pg_dump -Fc --no-acl --no-owner -d $HEROKU_DATABASE_URL | pg_restore --verbose --clean --no-acl --no-owner -d $DATABASE_URL/cusdis
```
```bash
fly secrets unset HEROKU_DATABASE_URL DATABASE_URL -a cusdis-db
```

Verify

```bash
fly pg connect -a cusdis-db -d cusdis
```

Exposing to external connections

(based on https://fly.io/docs/postgres/connecting/connecting-external/)

IP allocation

```bash
fly ips allocate-v4 -a cusdis-db
```

Expose external port

Pull down fly.toml configuration file
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```bash
fly config save --app cusdis-db
```
Update above configuration file
```toml
[[services]]
internal_port = 5432 # Postgres instance
protocol = "tcp"
[[services.ports]]
handlers = []
port = 10000
```

Deploy and verify changes

```bash
fly deploy -a cusdis-db --image flyio/postgres:14
fly info -a cusdis-db
```

Wrap up

By combining IP and public port above, we should be able to get the database url, something that looks like postgres://postgres:<pasword>@<host IPv4 address>:10000/cusdis . Just replace the old url with this new one and test with a few comments, then we should be 🥂.

Caveats

New incoming data to Heroku during the migration will be missed (see https://fly.io/docs/postgres/getting-started/migrate-from-heroku/ for more details)

Rename. i.e. replace cusdis-db appeared in above commands with your own app-db name