### Rihanna Database Upgrade Migration

Source: https://github.com/samsondav/rihanna/blob/master/CHANGELOG.md

Example of an Ecto migration file for upgrading Rihanna jobs.

```elixir
defmodule MyApp.UpgradeRihannaJobs do
  use Rihanna.Migration.Upgrade
end
```

--------------------------------

### Define Job Error Callback

Source: https://github.com/samsondav/rihanna/blob/master/CHANGELOG.md

Example of defining an `after_error` callback for a job to handle failure reasons and arguments.

```elixir
def after_error(failure_reason, args) do
  notify_someone(__MODULE__, failure_reason, args)
end
```

--------------------------------

### Set Default Priority

Source: https://github.com/samsondav/rihanna/blob/master/docs/upgrading_v2.md

Set the default value for the 'priority' column to 50 after the new code is running. This ensures new jobs or jobs without an explicit priority get a default value.

```sql
ALTER TABLE rihanna_jobs ALTER COLUMN priority SET DEFAULT 50;
```

--------------------------------

### Boot Rihanna Supervisor with Named Config (Without Ecto, Elixir 1.6+)

Source: https://github.com/samsondav/rihanna/blob/master/README.md

Add Rihanna.Supervisor to your application's children list, specifying a name and providing the Postgrex database configuration.

```elixir
children = [
  {Rihanna.Supervisor, [name: Rihanna.Supervisor, postgrex: My.Repo.config()]}
]
```

--------------------------------

### Boot Rihanna Supervisor with Named Config (Without Ecto, Elixir 1.5)

Source: https://github.com/samsondav/rihanna/blob/master/README.md

Add Rihanna.Supervisor to your application's children list using the supervisor macro, specifying a name and providing the Postgrex database configuration.

```elixir
import Supervisor.Spec, warn: false

children = [
  supervisor(Rihanna.Supervisor, [[name: Rihanna.Supervisor, postgrex: My.Repo.config()]])
]
```

--------------------------------

### Boot Rihanna Supervisor with Ecto Repo Config (Elixir 1.6+)

Source: https://github.com/samsondav/rihanna/blob/master/README.md

Add Rihanna.Supervisor to your application's children list, configuring it to use your Ecto Repo's database configuration.

```elixir
children = [
  {Rihanna.Supervisor, [postgrex: My.Repo.config()]}
]
```

--------------------------------

### Create Rihanna Database

Source: https://github.com/samsondav/rihanna/blob/master/CONTRIBUTING.md

Use this SQL command to create the necessary database for Rihanna to store its jobs. Ensure your PostgreSQL server is running.

```sql
-> psql
sql (10.5, server 9.6.10)
Type "help" for help.

(ins)username=# create database rihanna_db;
CREATE DATABASE
```

--------------------------------

### Boot Rihanna Supervisor with Ecto Repo Config (Elixir 1.5)

Source: https://github.com/samsondav/rihanna/blob/master/README.md

Add Rihanna.Supervisor to your application's children list using the supervisor macro, configuring it with your Ecto Repo's database configuration.

```elixir
import Supervisor.Spec, warn: false

children = [
  supervisor(Rihanna.Supervisor, [[postgrex: My.Repo.config()]])
]
```

--------------------------------

### Generate Rihanna Migration SQL

Source: https://github.com/samsondav/rihanna/blob/master/CONTRIBUTING.md

Run this command within an IEx session to generate the SQL for migrating your database schema. This SQL will create the 'rihanna_jobs' table and its primary key.

```elixir
-> iex -S mix
Erlang/OTP 21 [erts-10.0.4] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [hipe]

Interactive Elixir (1.7.1) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> IO.puts Rihanna.Migration.sql
CREATE TABLE rihanna_jobs (
... more sql ...
ALTER TABLE ONLY rihanna_jobs
ADD CONSTRAINT rihanna_jobs_pkey PRIMARY KEY (id);

:ok
```

--------------------------------

### Add Rihanna Dependency to mix.exs (Without Ecto)

Source: https://github.com/samsondav/rihanna/blob/master/README.md

Add the Rihanna dependency to your project's mix.exs file when not using Ecto.

```elixir
def deps do
  [
    {:rihanna, ">= 0.0.0"}
  ]
end
```

--------------------------------

### Enqueue Job with Mod-Fun-Args

Source: https://github.com/samsondav/rihanna/blob/master/README.md

Use this method for simple, immediate job enqueuing. The job is processed asynchronously.

```elixir
# Enqueue job for later execution and return immediately
Rihanna.enqueue({MyModule, :my_fun, [arg1, arg2]})
```

--------------------------------

### Add Rihanna Dependency to mix.exs (Ecto)

Source: https://github.com/samsondav/rihanna/blob/master/README.md

Add the Rihanna dependency to your project's mix.exs file when using Ecto.

```elixir
def deps do
  [
    {:rihanna, "~> 2.3"}
  ]
end
```

--------------------------------

### Configure Rihanna Ecto Producer Connection

Source: https://github.com/samsondav/rihanna/blob/master/README.md

Configure Rihanna to use your existing Ecto Repo for producer database connections. This enables Ecto sandbox usage in tests.

```elixir
config :rihanna,
  producer_postgres_connection: {Ecto, MyApp.Repo} # Use the name of your Repo here
```

--------------------------------

### Implement Rihanna.Job Behavior

Source: https://github.com/samsondav/rihanna/blob/master/README.md

Implement this behavior to define custom retry logic and error handling for jobs. The `perform/1` callback is required and receives job arguments as a single list.

```elixir
defmodule MyApp.MyJob do
  @behaviour Rihanna.Job

  # NOTE: `perform/1` is a required callback. It takes exactly one argument. To
  # pass multiple arguments, wrap them in a list and destructure in the
  # function head as in this example
  def perform([arg1, arg2]) do
    success? = do_some_work(arg1, arg2)

    if success? do
      # job completed successfully
      :ok
    else
      # job execution failed
      {:error, :failed}
    end
  end
end
```

--------------------------------

### Schedule Job at Specific Time

Source: https://github.com/samsondav/rihanna/blob/master/CHANGELOG.md

Schedule a job to run at a specific `DateTime` using Rihanna.

```elixir
Rihanna.schedule(
  {IO, :puts, ["Hello"]},
  at: DateTime.from_naive!(~N[2018-07-01 12:00:00], "Etc/UTC")
)
```

--------------------------------

### Schedule Job in Relative Time

Source: https://github.com/samsondav/rihanna/blob/master/CHANGELOG.md

Schedule a job to run in a specified duration using Rihanna.

```elixir
Rihanna.schedule({IO, :puts, ["Hello"]}, in: :timer.hours(1))
```

--------------------------------

### Fix Rihanna Jobs Index

Source: https://github.com/samsondav/rihanna/blob/master/README.md

Recreate the `rihanna_jobs_locking_index` to ensure correct sorting with NULL values for `due_at`.

```sql
CREATE INDEX CONCURRENTLY rihanna_jobs_locking_index_fixed ON rihanna_jobs (priority ASC, due_at ASC NULLS FIRST, enqueued_at ASC, id ASC);
DROP INDEX rihanna_jobs_locking_index;
ALTER INDEX rihanna_jobs_locking_index_fixed RENAME TO rihanna_jobs_locking_index;
```

--------------------------------

### Create Rihanna Jobs Table Migration (Ecto)

Source: https://github.com/samsondav/rihanna/blob/master/README.md

Define a migration to create the 'rihanna_jobs' table in your database when using Ecto.

```elixir
defmodule MyApp.CreateRihannaJobs do
  use Rihanna.Migration
end
```

--------------------------------

### Add Priority Column and Create Index

Source: https://github.com/samsondav/rihanna/blob/master/docs/upgrading_v2.md

Directly alter the database table to add a 'priority' column and create a new concurrent index. This is part of the 'Direct SQL upgrade' option.

```sql
ALTER TABLE rihanna_jobs ADD COLUMN priority integer;
CREATE INDEX CONCURRENTLY rihanna_jobs_locking_index ON rihanna_jobs (priority ASC, due_at ASC NULLS FIRST, enqueued_at ASC, id ASC);
```

--------------------------------

### Enqueue Custom Job Implementation

Source: https://github.com/samsondav/rihanna/blob/master/README.md

Enqueue jobs that implement the `Rihanna.Job` behavior. This allows for custom logic defined within the job module.

```elixir
# Enqueue job for later execution and return immediately
Rihanna.enqueue({MyApp.MyJob, [arg1, arg2]}, opts)
```

--------------------------------

### Insert Migration Version

Source: https://github.com/samsondav/rihanna/blob/master/docs/upgrading_v2.md

Manually insert the migration version into the `schema_migrations` table. This is required when performing a direct SQL upgrade to bypass the migration file execution.

```sql
INSERT INTO schema_migrations VALUES (YOUR_MIGRATION_VERSION_HERE, now());
```

--------------------------------

### Backfill Null Priority Jobs

Source: https://github.com/samsondav/rihanna/blob/master/docs/upgrading_v2.md

Update existing jobs where the 'priority' column is null to have a default value of 50. This ensures data consistency after the column addition.

```sql
UPDATE rihanna_jobs SET priority = 50 WHERE priority IS NULL;
```

--------------------------------

### Set Priority Column to Not Null

Source: https://github.com/samsondav/rihanna/blob/master/docs/upgrading_v2.md

Make the 'priority' column a non-nullable column after backfilling any null values. This enforces data integrity for the priority field.

```sql
ALTER TABLE rihanna_jobs ALTER COLUMN priority SET NOT NULL;
```

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