Debugging Rails Active Jobs with the Vanilla Adapters

Short reference on how to quickly debug the vanilla Rails job adapters.

Queue Adapters by Environment

Development (:async)

Jobs run in background threads ( Concurrent Ruby ThreadPoolExecutor Show archive.org snapshot ) within the process that called the job.

• Jobs execute immediately in a background thread within bin/rails s and write to the server logs.
• bin/jobs does nothing in development, jobs already run in-process via :async.
• Scripts and rake tasks log go to log/development.log

Watch out for this within the Rails or development logs:

CopyEnqueued HelloJob (Job ID: xxx) to Async(asap)
Performing HelloJob (Job ID: xxx)
Performed HelloJob (Job ID: xxx) in 3.5s

For quick debugging, add logging or run synchronously to add a debugger:

Copy# Skip queue, run immediately in current thread
HelloJob.perform_now(membership)

class HelloJob
  def perform
    puts "Hello" # → stdout of calling process (server or script terminal)
    Rails.logger.info "Hello" # → log/development.log (always)
    debbuger # → Work only when called within `perform_now`
  end
end

Use tail -f log/development.log or tail -f log/development.log | grep -i Hello

perform_later vs perform_now

Within perform_later the debugger will just shut down once your main process is killed or finished. Until then it will hang there waiting for input and is blocking the job.

Production (:solid_queue)

• Jobs persist to solid_queue_* tables.
• Requires bin/jobs worker running.
• You can also check /log/production.log.

Copy# Check pending jobs
SolidQueue::ReadyExecution.count

# Check failed jobs
SolidQueue::FailedExecution.last&.error

# Find specific job
SolidQueue::Job.where(class_name: 'HelloJob').last

Test (:test)

Jobs are not executed and only stored for assertions.

• Spawning a debugger will work independent from using perform_now or perform_later.
• For system tests you can check /log/test.log.

Copyassert_enqueued_with(job: HelloJob, args: [membership])

# Or execute all queued jobs
perform_enqueued_jobs do
  HelloJob.perform_later('matthew')
  assert_performed_jobs 1
end

Further Reading

• Concurrent Ruby ThreadPoolExecutor Show archive.org snapshot : The thread pool backing :async
• Rails AsyncAdapter source Show archive.org snapshot : How Rails wraps Concurrent Ruby
• Solid Queue Show archive.org snapshot : The production queue backend