Elixir + docker compose Connection with postgres refused

Question

Hello I have a problem connecting to postgres with the elixir, I tried the following on docker-compose:

I used environment variables, but it wasn’t so I tried putting string in dev.exs, but even then it still rejects the connection.

I tested my postgres and it works normally and has the database created all right log:

postgres-db | 2021-02-23 22:46:30.410 UTC [1] LOG: database system is ready to accept connections

.env:

DB_NAME=spiritpay-dev
DB_USER=postgres
DB_HOST=localhost
DB_PASS=12345

docker-compose:

version: "3.7"
services:
  app:
      restart: on-failure
      environment: 
        DB_USER: postgres
        DB_PASSWORD: 12345
        DB_NAME: spiritpay-dev
        DB_HOST: postgres-db
      build: .
      command: /bin/sh docker-entrypoint.sh
      ports: 
        - "4000:4000"
      depends_on: 
        - postgres-db 
      links:
        - postgres-db
  postgres-db:
      image: "postgres:12"
      restart: always
      container_name: "postgres-db"
      environment: 
        POSTGRES_PASSWORD: ${DB_PASS}
        POSTGRES_USER: ${DB_USER}
        POSTGRES_DB: ${DB_NAME}
      ports: 
        - "5433:5433"

dev.exs:

use Mix.Config

# Configure your database
config :spiritpay, Spiritpay.Repo,
  username: "postgres",
  password: "12345",
  database: "spiritpay-dev",
  hostname: "postgres-db",
  port: 5433,
  show_sensitive_data_on_connection_error: true,
  pool_size: 10

# For development, we disable any cache and enable
# debugging and code reloading.
#
# The watchers configuration can be used to run external
# watchers to your application. For example, we use it
# with webpack to recompile .js and .css sources.
config :spiritpay, SpiritpayWeb.Endpoint,
  http: [port: 4000],
  debug_errors: true,
  code_reloader: true,
  check_origin: false,
  watchers: []

# ## SSL Support
#
# In order to use HTTPS in development, a self-signed
# certificate can be generated by running the following
# Mix task:
#
#     mix phx.gen.cert
#
# Note that this task requires Erlang/OTP 20 or later.
# Run `mix help phx.gen.cert` for more information.
#
# The `http:` config above can be replaced with:
#
#     https: [
#       port: 4001,
#       cipher_suite: :strong,
#       keyfile: "priv/cert/selfsigned_key.pem",
#       certfile: "priv/cert/selfsigned.pem"
#     ],
#
# If desired, both `http:` and `https:` keys can be
# configured to run both http and https servers on
# different ports.

# Do not include metadata nor timestamps in development logs
config :logger, :console, format: "[$level] $message\n"

# Set a higher stacktrace during development. Avoid configuring such
# in production as building large stacktraces may be expensive.
config :phoenix, :stacktrace_depth, 20

# Initialize plugs at runtime for faster development compilation
config :phoenix, :plug_init_mode, :runtime

logs:

app_1 | 22:46:31.020 [error] GenServer #PID<0.368.0> terminating app_1 | ** (DBConnection.ConnectionError) tcp connect (postgres-db:5433): connection refused - :econnrefused app_1
| (db_connection 2.3.1) lib/db_connection/connection.ex:100: DBConnection.Connection.connect/2 app_1 | (connection 1.1.0) lib/connection.ex:622: Connection.enter_connect/5 app_1 | (stdlib 3.14) proc_lib.erl:226: :proc_lib.init_p_do_apply/3 app_1 | Last message: nil app_1 | State: Postgrex.Protocol app_1 | ** (Mix) The database for Spiritpay.Repo couldn't be dropped: killed app_1 | [error] Postgrex.Protocol (#PID<0.330.0>) failed to connect: ** (DBConnection.ConnectionError) tcp connect (postgres-db:5433): connection refused - :econnrefused

Andreas Andreas · Accepted Answer · 2021-02-23T22:59:25

Point 1:

Try replacing localhost by postgres-db in .env since the host of your database is that. You docker compose maps internal hosts to service names

Excerpt from the docs :

By default Compose sets up a single network for your app. Each container for a service joins the default network and is both reachable by other containers on that network, and discoverable by them at a hostname identical to the container name.

Point2:

add .env to your app service:

services:
  app:
      restart: on-failure
      build: .
      command: /bin/sh docker-entrypoint.sh
      ports: 
        - "4000:4000"
      depends_on: 
        - postgres-db 
      links:
        - postgres-db
      env_file:
         - .env

In the above example you configuration seems vake you your environment variables defined in 3 places

in .env which is not used
in environment section of app service
hardcoded in dev.exs the above will only create confusion and burden

in dev.exs load configuration from environment

Point3

the port number you use is wrong postgres operates on 5432

Point 4:

You can test connection from host machine by listening to connections from everywhere 0.0.0.0 using:

    ports:
      - 0.0.0.0:5432:5432

then you can test connection on localhost using netcat: nc -v localhost 5432

Elixir + docker compose Connection with postgres refused

1 Answers