implement-background-job

Implement Background Job

Apply the execution contract before this procedure.

Use this skill when the task is to add, configure, or review background jobs in a Rails application.

HARD-GATE

EVERY job MUST have its test written and validated BEFORE implementation:
  1. Write the job spec (idempotency, retry, error handling)
  2. Run the spec — verify it fails
  3. ONLY THEN write the job class

The authoritative perform contract — EVERY perform method does exactly three things:
  1. Load the record from the passed ID
  2. Guard for idempotency / permanent no-op conditions
  3. Delegate the side effect or orchestration to a service object

If perform needs more than that, extract a service.
EVERY job that performs a side effect (charge, email, API call) MUST have
an idempotency check BEFORE the side effect.

Core Rules

Core Process

1. Write the job spec first — idempotency, retry, and error handling — and run it to confirm it fails.
2. Write the job class following the perform contract in HARD-GATE.
3. Add retry_on with explicit attempts: limit and discard_on for at least one permanent error.
4. Run the full test suite.
5. Enqueue or perform the job twice — confirm the second run is a no-op.
6. For recurring jobs, define them in config/recurring.yml (Rails 8) or the chosen scheduler config.

Extended Resources

Rails 8 vs Rails 7

Examples

Thin job with idempotency and retry:

class SendInvoiceReminderJob < ApplicationJob
  queue_as :default
  retry_on Net::OpenTimeout, wait: :polynomially_longer, attempts: 5
  discard_on ActiveRecord::RecordNotFound

  def perform(invoice_id)
    invoice = Invoice.find(invoice_id)
    return if invoice.reminder_sent_at?

    InvoiceReminders::Send.call(invoice:)
  end
end

Service owns the side effect and state update:

module InvoiceReminders
  class Send
    def self.call(invoice:)
      InvoiceMailer.overdue(invoice).deliver_now
      invoice.update!(reminder_sent_at: Time.current)
    end
  end
end

• BACKENDS.md — Solid Queue vs Sidekiq setup, configuration details, and Redis requirements.

Load these files only when their specific content is needed:

• [assets/job_patterns.md](assets/job_patterns.md) — Use when implementing multi-step orchestration or batch job patterns
• [assets/retry_examples.md](assets/retry_examples.md) — Use when configuring retry_on/discard_on for specific error classes beyond the basic patterns above

Output Checklist

• [ ] Backend decision stated (Rails version/scale → Solid Queue or Sidekiq)
• [ ] Job spec shown first; command run; confirms failure before implementation
• [ ] perform receives IDs, loads record, guards idempotency, delegates to service
• [ ] retry_on with attempts: limit and discard_on for permanent error
• [ ] Double-run verification confirms second run is a no-op
• [ ] Recurring job (if any) defined in config/recurring.yml or scheduler config
• [ ] If ops docs requested: record backend, retry, recurring schedule, and idempotency decisions in process_log.md

Integration