Scheduled jobs in Ruby on Rails - Step-by-Step Execution

Concept Flow - Scheduled jobs

Define job class

↓

Schedule job with interval

↓

Job queue stores job

↓

Background worker picks job

↓

Job performs task

↓

Job completes and logs

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Wait for next scheduled time

Scheduled jobs in Rails define tasks to run later or repeatedly, managed by background workers that pick and execute them on time.

Execution Sample

Ruby on Rails

class CleanupJob < ApplicationJob
  queue_as :default

  def perform
    User.where('last_sign_in_at < ?', 1.year.ago).delete_all
  end
end

CleanupJob.set(wait: 1.hour).perform_later

This code schedules a job to delete users inactive for over a year, running one hour later.

Execution Table

Step	Action	Job State	Worker Action	Output/Result
1	Define CleanupJob class	Job class ready	No worker action	Ready to schedule
2	Schedule job with wait: 1.hour	Job queued with timestamp	No worker action	Job stored in queue
3	Background worker checks queue	Job queued	No job ready yet	Wait for scheduled time
4	One hour passes	Job ready to run	Worker picks job	Job starts performing
5	Perform job: delete old users	Job running	Worker executes perform method	Old users deleted
6	Job completes	Job done	Worker logs completion	Job finished successfully
7	Wait for next scheduled job	No job queued	Idle or picks next job	Ready for next task

💡 Job finishes after performing task; worker waits for next scheduled job.

Variable Tracker

Variable	Start	After Step 2	After Step 4	After Step 5	Final
Job State	Not defined	Queued with timestamp	Ready to run	Running	Done
Worker Status	Idle	Idle	Picks job	Executes job	Idle

Key Moments - 3 Insights

Why doesn't the job run immediately after scheduling?

Because the job is scheduled with a delay (wait: 1.hour), the worker waits until the scheduled time before running it, as shown in steps 3 and 4.

What happens if the worker checks the queue but the job is not ready?

The worker stays idle or checks other jobs until the scheduled time arrives, as seen in step 3 where no job runs yet.

How does the job know what task to perform?

The job class defines the perform method with the task code; the worker calls this method when running the job (step 5).

Visual Quiz - 3 Questions

Look at the execution table, what is the Job State at Step 4?

A Queued with timestamp

B Running

C Ready to run

D Done

💡 Hint

Check the 'Job State' column at Step 4 in the execution_table.

At which step does the worker start executing the job's perform method?

A Step 5

B Step 4

C Step 3

D Step 6

💡 Hint

Look for when 'Worker executes perform method' happens in the execution_table.

If the job was scheduled with wait: 0.seconds, how would Step 3 change?

A Job would remain queued longer

B Worker would pick job immediately, no waiting

C Worker would ignore the job

D Job would be deleted

💡 Hint

Consider the 'Job queued with timestamp' and worker action timing in Step 3.

Concept Snapshot

Scheduled jobs in Rails run tasks later or repeatedly.
Define a job class with perform method.
Schedule with set(wait: time).perform_later.
Background workers run jobs at scheduled time.
Useful for cleanup, emails, reports.

Full Transcript

Scheduled jobs in Rails let you run code later or repeatedly without blocking the main app. You create a job class inheriting from ApplicationJob and define a perform method with the task. Then you schedule it using set(wait: time).perform_later, which queues the job with a timestamp. Background workers check the queue and run jobs when their scheduled time arrives. This process helps keep your app responsive by handling tasks like deleting old users or sending emails in the background. The execution table shows each step from defining the job to completion, tracking job state and worker actions. Key points include understanding the delay before execution and how the worker picks and runs the job. This visual trace helps beginners see how scheduled jobs flow in Rails.