Drop database with Elixir releases


My Phoenix application is deployed on Gigalixir but using a database hosted on Google Cloud Platform. I use Elixir releases for deployment.

I am still in the pre-production phase of development so all I have running is a staging environment that my teammates can access and use for testing as the application is being developed. And I’m having issues dropping the database on the staging environment. I followed the method outlined in Deploying with Releases and came up with the following Backend.Release module:

defmodule Backend.Release do
  @app :backend

  def ecto_drop do

    for repo <- repos() do

  defp drop_database(repo) do
    case repo.__adapter__.storage_down(repo.config) do
      :ok ->
        IO.puts "The database for #{inspect repo} has been dropped"
      {:error, :already_down} ->
        IO.puts "The database for #{inspect repo} has already been dropped"
      {:error, term} when is_binary(term) ->
        raise "The database for #{inspect repo} couldn't be dropped: #{term}"
      {:error, term} ->
        raise "The database for #{inspect repo} couldn't be dropped: #{inspect term}"

  defp repos do
    Application.fetch_env!(@app, :ecto_repos)

  defp load_app do

The code for drop_database came straight from the code for ecto.drop, with the removal of references to Mix.

I run this with Gigalixir:

$ gigalixir ps:remote_console

iex > Backend.Release.ecto_drop()

** (RuntimeError) The database for Backend.Repo couldn't be dropped: ERROR 55006 (object_in_use) database "master" is being accessed by other users

There are 2 other sessions using the database.
    (backend) lib/backend/release.ex:19: Backend.Release.drop_database/1
    (backend) lib/backend/release.ex:8: anonymous fn/2 in Backend.Release.ecto_drop/0
    (elixir) lib/enum.ex:1948: Enum."-reduce/3-lists^foldl/2-0-"/3
    (backend) lib/backend/release.ex:7: Backend.Release.ecto_drop/0

I imagine the 2 sessions are:

  • the “regular” web server
  • the iex console that I just started to run the command

It seems like it’s a chicken and egg problem. To drop the database, the database can’t be accessed by others. But to be able to drop the database, I need to run an iex console, which starts a connection to the database. Or am I wrong about this?

Any thoughts on how I can drop the remote database using Elixir releases?

Thank you in advance.


Try the following:

Enter remote console:

gigalixir ps:remote_console

Then run your command:

_build/prod/rel/release_name/bin/release_name eval "Backend.Release.ecto_drop"

This way you never need to invoke iex.

See Ecto migrations and custom commands section in phoenix documentation Deploying with Releases


Thanks for the proposal! But unfortunately that didn’t work either. It looks like I can’t enter a remote console on Gigalixir without having at least one replica running, thereby making it impossible to drop the database. I ended up recreating the database on GCP.