I'm upgrading an app to Rails 6 and after fixing all breaking changes I'm now facing an error when sending emails from background jobs.
I use Sidekiq through ActiveJob and I believe I've added the necessary config changes:
# config/application.rb
...
config.load_defaults 6.0
# config/initializers/new_framework_defaults_6_0.rb
...
Rails.application.config.action_mailer.delivery_job = "ActionMailer::MailDeliveryJob"
I'm sending emails using deliver_later, like: UserMailer.notify(user).deliver_later
One important aspect is that the emails ARE being delivered even though I'm getting the error
Error message:
NameError:
uninitialized constant ActionMailer::MailDeliveryJob
Did you mean? ActionMailer::DeliveryJob
According to Rollbar the context of the error is ActiveJob::QueueAdapters::SidekiqAdapter::JobWrapper
Any help is appreciated, thanks!
ActionMailer::MailDeliveryJob is new for rails 6, previously it was called ActionMailer::DeliveryJob (and is still present in rails 6 but with deprecation warning for smoother migration)
Looks like you have a situation when jobs from new rails ended up in a sidekiq worker that is still running previous version. Since emails are actually being delivered - most probably you have workers with both rails versions at the same time. Some workers generate the error and job is retried until it is picked by a worker that finally delivers.
To prevent the error it's better to deploy with action_mailer.delivery_job = "ActionMailer::DeliveryJob", make sure all workers are upgraded (=restarted with new code) and only then remove deprecation warning by switching to MailDeliveryJob.