Issue with Understanding Phoenix Project Deployment

Phoenix Forum Questions / Help
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Hi friends,

I am very new to Phoenix and PostgreSQL database. I am trying to deploy a simple very basic web app on fly.io to try to understand the deployment process so that I can adapt to my existing projects but I am very lost and confused. Here’s what I did.

mix phx.new Testing --app testing123

cd Testing

mix ecto.create

And then I used fly launch and fly deploy command. I got the following errors.

** (RuntimeError) environment variable DATABASE_URL is missing.
For example: ecto://USER:PASS@HOST/DATABASE

What I don’t understand here is the DATABASE_URL. How do I construct one?

When I do brew services list, I have postgresql@15 running already. If I do, psql testing123_dev and do \conninfo, I got "You are connected to database “testing123_dev” as user “sawwerakyawkyaw” via socket in “/tmp” at port “5432”.

Does that mean my DATABASE_URL is ecto://sawwerakyawkyaw:PASS@localhost:5432/testing123_dev?

Also, for each Phoenix project that I create, am I going to need unique DATABASE_URL for each one?

I am very lost and confused. If you can answer my questions or you know any resources to learn more about understanding postgres databases and/ or how to properly deploy, I would really appreciate it.

Many thanks.

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See the docs for Ecto URLs.

You have it running on your personal machine. If you are deploying an app to a service (Flyio) then you probably want a database running on that service too. They have a few different options, so consult their docs. I think the easy one was their integration with supabase, but they are working on their own managed postgres too. I would avoid their old “HA Postgres” non-managed offering (if it still exists), given it sounds like you’re new to this.

That depends on if you want a unique database for each one. Most likely you would use a separate database for each project, but Postgres can host multiple databases on the same server (confusingly called a “cluster”).

If you host multiple databases on the same server, you will probably have a unique user/database/pass for each one but the same host/port.

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Hey! Thank you so much. You have enlightened me about the deployment process. I actually start reading the fly.io documentation and I start to understand a lot things. This is just the beginning. People like you make the learning process much more fun!

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