How you would configure elixir app with ecto to connect with postgres on host machine?

Learning Questions & Discussions What/How...
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1

I’ve added ecto to my Elixir app. On host it’s running fine, because ecto can connect to local db. But I don’t understand, what i need to do, if this app running in docker container.

I’m getting this error:
11:42:31.536 [error] Postgrex.Protocol (#PID<0.249.0>) failed to connect: ** (DBConnection.ConnectionError) tcp connect (localhost:5432): connection refused - :econnrefused

And I understand, that docker container with my app doesn’t have postgresql at localhost inside. But i don’t understand, how configure this.

P.S. I’m trying to learn Docker, Elixir, Ecto, Postgresql.

My app on github, branch - main, not master.

2

Instead of localhost connect to whatever the hostname of postgres is in your docker setup. What that is depends on your general setup – postgres within docker or postgres on the host running docker – as well as potentially the specific name you gave things.

3

My postgres runs at host machine, not in container. Where i can find hostname of postgres?

4
1 Like
5

That works!

config :echo, Echo.Repo,
  database: "echo_db",
  username: "postgres",
  password: "postgres",
  hostname: "host.docker.internal"

Thank you, but now i can’t start my app localy on machine. How can i split configuration of ecto for docker, and for local using?

6

https://hexdocs.pm/elixir/Config.html#import_config/1

7

Maybe you could do stuff like this in your dev.exs

get_db_host = fn -> 
  if File.exists?("/.dockerenv") do
    "host.docker.internal"
  else
    "pg host outside docker"
  end
end

config :echo, Echo.Repo
    ...
    hostname: get_db_host.()

But it’s also possible to read it from the environment by using;

config :echo, Echo.Repo
   ...
   database: System.get_env("PGHOST", "host.docker.internal")

then outside of the docker you have to set PGHOST before starting things up.

1 Like
8

I’ve find another way of solving this problem.

Uncommented this line from config/config.exs

import_config "#{config_env()}.exs"

Added docker.exs with

import Config


config :echo, Echo.Repo,
  database: "echo_db",
  username: "postgres",
  password: "postgres",
  hostname: "host.docker.internal"

Added to up of Dockerfile

ENV MIX_ENV docker
9

Yeah, i have read this before, but don’t understand how use this. Now i know

10

Yeah this is even another way of doing it and maybe the cleanest way.

Great you found a good solution! Happy elixiring! :slight_smile: