Oban Designer

Installation

# mix.exs
{:oban, "~> 2.18"}

# config/config.exs
config :my_app, Oban,
  repo: MyApp.Repo,
  queues: [default: 10, mailers: 20, webhooks: 50, events: 5],
  plugins: [
    Oban.Plugins.Pruner,
    {Oban.Plugins.Cron, crontab: [
      {"0 2 * * *", MyApp.Workers.DailyCleanup},
      {"*/5 * * * *", MyApp.Workers.MetricsCollector}
    ]}
  ]

# In application.ex children:
{Oban, Application.fetch_env!(:my_app, Oban)}

Generate the Oban migrations:

mix ecto.gen.migration add_oban_jobs_table

defmodule MyApp.Repo.Migrations.AddObanJobsTable do
  use Ecto.Migration
  def up, do: Oban.Migration.up(version: 12)
  def down, do: Oban.Migration.down(version: 1)
end

Worker Implementation

Basic Worker

defmodule MyApp.Workers.SendEmail do
  use Oban.Worker,
    queue: :mailers,
    max_attempts: 5,
    priority: 1

  @impl Oban.Worker
  def perform(%Oban.Job{args: %{"to" => to, "template" => template} = args}) do
    case MyApp.Mailer.deliver(to, template, args) do
      {:ok, _} -> :ok
      {:error, :temporary} -> {:error, "temporary failure"}  # Will retry
      {:error, :permanent} -> {:cancel, "invalid address"}   # Won't retry
    end
  end
end

Return Values

Queue Configuration

See references/worker-patterns.md for common worker patterns.

Sizing Guidelines

Queue Priority

Jobs within a queue execute by priority (0 = highest). Use sparingly:

%{user_id: user.id}
|> MyApp.Workers.SendEmail.new(priority: 0)  # Urgent
|> Oban.insert()

Retry Strategies

Default Backoff

Oban uses exponential backoff: attempt^4 + attempt seconds.

Custom Backoff

defmodule MyApp.Workers.WebhookDelivery do
  use Oban.Worker,
    queue: :webhooks,
    max_attempts: 10

  @impl Oban.Worker
  def backoff(%Oban.Job{attempt: attempt}) do
    # Exponential with jitter: 2^attempt + random(0..30)
    trunc(:math.pow(2, attempt)) + :rand.uniform(30)
  end

  @impl Oban.Worker
  def perform(%Oban.Job{args: args}) do
    # ...
  end
end

Timeout

use Oban.Worker, queue: :media

@impl Oban.Worker
def timeout(%Oban.Job{args: %{"size" => "large"}}), do: :timer.minutes(10)
def timeout(_job), do: :timer.minutes(2)

Uniqueness

Prevent duplicate jobs:

defmodule MyApp.Workers.SyncAccount do
  use Oban.Worker,
    queue: :default,
    unique: [
      period: 300,               # 5 minutes
      states: [:available, :scheduled, :executing, :retryable],
      keys: [:account_id]        # Unique by this arg key
    ]
end

Unique Options

Replace Existing

%{account_id: id}
|> MyApp.Workers.SyncAccount.new(
  replace: [:scheduled_at],    # Update scheduled_at if duplicate
  schedule_in: 60
)
|> Oban.insert()

Cron Scheduling

# config.exs
plugins: [
  {Oban.Plugins.Cron, crontab: [
    {"0 */6 * * *", MyApp.Workers.DigestEmail},
    {"0 2 * * *", MyApp.Workers.DailyCleanup},
    {"0 0 1 * *", MyApp.Workers.MonthlyReport},
    {"*/5 * * * *", MyApp.Workers.HealthCheck, args: %{service: "api"}},
  ]}
]

Cron expressions: minute hour day_of_month month day_of_week.

Inserting Jobs

# Immediate
%{user_id: user.id, template: "welcome"}
|> MyApp.Workers.SendEmail.new()
|> Oban.insert()

# Scheduled
%{report_id: id}
|> MyApp.Workers.GenerateReport.new(schedule_in: 3600)
|> Oban.insert()

# Scheduled at specific time
%{report_id: id}
|> MyApp.Workers.GenerateReport.new(scheduled_at: ~U[2024-01-01 00:00:00Z])
|> Oban.insert()

# Bulk insert
changesets = Enum.map(users, fn user ->
  MyApp.Workers.SendEmail.new(%{user_id: user.id})
end)
Oban.insert_all(changesets)

# Inside Ecto.Multi
Ecto.Multi.new()
|> Ecto.Multi.insert(:user, changeset)
|> Oban.insert(:welcome_email, fn %{user: user} ->
  MyApp.Workers.SendEmail.new(%{user_id: user.id})
end)
|> Repo.transaction()

Oban Pro Features

Available with Oban Pro license:

Batch (group of jobs)

# Process items in batch, run callback when all complete
batch = MyApp.Workers.ProcessItem.new_batch(
  items |> Enum.map(&%{item_id: &1.id}),
  callback: {MyApp.Workers.BatchComplete, %{batch_name: "import"}}
)
Oban.insert_all(batch)

Workflow (job dependencies)

Oban.Pro.Workflow.new()
|> Oban.Pro.Workflow.add(:extract, MyApp.Workers.Extract.new(%{file: path}))
|> Oban.Pro.Workflow.add(:transform, MyApp.Workers.Transform.new(%{}), deps: [:extract])
|> Oban.Pro.Workflow.add(:load, MyApp.Workers.Load.new(%{}), deps: [:transform])
|> Oban.insert_all()

Chunk (aggregate multiple jobs)

defmodule MyApp.Workers.BulkIndex do
  use Oban.Pro.Workers.Chunk,
    queue: :indexing,
    size: 100,            # Process 100 at a time
    timeout: 30_000       # Or after 30s

  @impl true
  def process(jobs) do
    items = Enum.map(jobs, & &1.args)
    SearchIndex.bulk_upsert(items)
    :ok
  end
end

Testing

See references/testing-oban.md for detailed testing patterns.

Setup

# config/test.exs
config :my_app, Oban,
  testing: :manual  # or :inline for synchronous execution

# test_helper.exs (if using :manual)
Oban.Testing.start()

Asserting Job Enqueued

use Oban.Testing, repo: MyApp.Repo

test "enqueues welcome email on signup" do
  {:ok, user} = Accounts.register(%{email: "test@example.com"})

  assert_enqueued worker: MyApp.Workers.SendEmail,
    args: %{user_id: user.id, template: "welcome"},
    queue: :mailers
end

Executing Jobs in Tests

test "processes email delivery" do
  {:ok, _} =
    perform_job(MyApp.Workers.SendEmail, %{
      "to" => "user@example.com",
      "template" => "welcome"
    })
end

Monitoring

Telemetry Events

# Attach in application.ex
:telemetry.attach_many("oban-logger", [
  [:oban, :job, :start],
  [:oban, :job, :stop],
  [:oban, :job, :exception]
], &MyApp.ObanTelemetry.handle_event/4, %{})

Key Metrics to Track

• Job execution duration (p50, p95, p99)
• Queue depth (available jobs per queue)
• Error rate per worker
• Retry rate per worker