Hi everyone!
In this post, I would like to share the migration script (migrate, rollback by step and seeding data) when releasing a Phoenix/OTP application. This script is extended from original Running Migration documentation of Distillery’s creator, I and my colleagues - we wrote more functions to support database rollback and seeding data.
Step 1:
- Init a new module
# apps/myapp/lib/migration.ex
defmodule MyApp.ReleaseTasks do
@start_apps [
:postgrex,
:ecto
]
@app :myapp
def repos, do: Application.get_env(@app, :ecto_repos, [])
def seed do
prepare()
# Run seed script
Enum.each(repos(), &run_seeds_for/1)
# Signal shutdown
IO.puts("Success!")
end
defp run_seeds_for(repo) do
# Run the seed script if it exists
seed_script = seeds_path(repo)
if File.exists?(seed_script) do
IO.puts("Running seed script..")
Code.eval_file(seed_script)
end
end
def migrate do
prepare()
Enum.each(repos(), &run_migrations_for/1)
IO.puts("Migrations successful!")
end
defp run_migrations_for(repo) do
app = Keyword.get(repo.config, :otp_app)
IO.puts("Running migrations for #{app}")
Ecto.Migrator.run(repo, migrations_path(repo), :up, all: true)
end
def rollback do
prepare()
get_step =
IO.gets("Enter the number of steps: ")
|> String.trim()
|> Integer.parse()
case get_step do
{int, _trailing} ->
Enum.each(repos(), fn repo -> run_rollbacks_for(repo, int) end)
IO.puts("Rollback successful!")
:error ->
IO.puts("Invalid integer")
end
end
defp run_rollbacks_for(repo, step) do
app = Keyword.get(repo.config, :otp_app)
IO.puts("Running rollbacks for #{app} (STEP=#{step})")
Ecto.Migrator.run(repo, migrations_path(repo), :down, all: false, step: step)
end
defp prepare do
IO.puts("Loading #{@app}..")
# Load the code for myapp, but don't start it
:ok = Application.load(@app)
IO.puts("Starting dependencies..")
# Start apps necessary for executing migrations
Enum.each(@start_apps, &Application.ensure_all_started/1)
# Start the Repo(s) for myapp
IO.puts("Starting repos..")
Enum.each(repos(), & &1.start_link(pool_size: 1))
end
defp seeds_path(repo), do: priv_path_for(repo, "seeds.exs")
defp priv_path_for(repo, filename) do
app = Keyword.get(repo.config, :otp_app)
IO.puts("App: #{app}")
repo_underscore = repo |> Module.split() |> List.last() |> Macro.underscore()
Path.join([priv_dir(app), repo_underscore, filename])
end
defp priv_dir(app), do: "#{:code.priv_dir(app)}"
end
Step 2:
Create shell script files to call functions:
- Migrate script at
rel/commands/migrate.sh
#!/bin/sh
$RELEASE_ROOT_DIR/bin/myapp command Elixir.MyApp.ReleaseTasks migrate
- Seed script at
rel/commands/seed.sh
#!/bin/sh
$RELEASE_ROOT_DIR/bin/myapp command Elixir.MyApp.ReleaseTasks seed
- Rollback script at
rel/commands/rollback.sh
#!/bin/sh
$RELEASE_ROOT_DIR/bin/myapp command Elixir.MyApp.ReleaseTasks rollback
Step 3:
Setup commands from rel/config.exs
release :myapp do
set version: current_version(:myapp)
set applications: [
:runtime_tools,
:misc_random,
admin: :permanent, graphql: :permanent,
redis: :permanent,
session: :permanent,
myapp: :permanent
]
set commands: [
"seed": "rel/commands/seed.sh",
"migrate": "rel/commands/migrate.sh",
"rollback": "rel/commands/rollback.sh",
]
end
Step 4:
Once you have deployed the application, you can run:
- Migrate
bin/myapp migrate
- Seed
bin/myapp seed
- Rollback. You can specify how many steps you wanna rollback
bin/myapp rollback
You guys can download the code from my gist. Thanks!
Top comments (0)