How to notify a user after background task is finished? - ruby-on-rails

Question

I use rails with ActiveJob and sidekiq as backend. When user come on a page sidekiq create a long-term background task, how can I notice a user (by render partial on the web page) when a task would be completed?
Rails and sidekiq work as different processes. This fact confused me I don't understand how to handle completed status using background job.

Answer 1

ActiveJob provides an after_perform callback which according to docs work like this:
class VideoProcessJob < ActiveJob::Base
queue_as :default
after_perform do |job|
UserMailer.notify_video_processed(job.arguments.first)
end
def perform(video_id)
Video.find(video_id).process
end
end
So, you don't have to worry to integrate directly with Sidekiq or any other queuing backend, talk to ActiveJob :)

Answer 2

My approach in this situation is:
Add sidekiq-status so that background jobs can be tracked by ID.
In the client call that creates the background job, return the newly-created job's ID.
class MyController < ApplicationController
def create
# sidekiq-status lets us retrieve a unique job ID when
# creating a job
job_id = Workers::MyJob.perform_async(...)
# tell the client where to find the progress of this job
return :json => {
:next => "/my/progress?job_id={job_id}"
}
end
end
Poll a 'progress' endpoint on the server with that job ID. This endpoint fetches job progress information for the job and returns it to the client.
class MyController < ApplicationController
def progress
# fetch job status from sidekiq-status
status = Sidekiq::Status::get_all(params[:job_id])
# in practice, status can be nil if the info has expired from
# Redis; I'm ignoring that for the purpose of this example
if status["complete"]
# job is complete; notify the client in some way
# perhaps by sending it a rendered partial
payload = {
:html => render_to_string({
:partial => "my/job_finished",
:layout => nil
})
}
else
# tell client to check back again later
payload = {:next => "/my/progress?job_id={params[:job_id]}"}
end
render :json => payload
end
end
If the client sees that the job has completed, it can then display a message or take whatever next step is required.
var getProgress = function(progress_url, poll_interval) {
$.get(progress_url).done(function(progress) {
if(progress.html) {
// job is complete; show HTML returned by server
$('#my-container').html(progress.html);
} else {
// job is not yet complete, try again later at the URL
// provided by the server
setTimeout(function() {
getProgress(progress.next, poll_interval);
}, poll_interval);
}
});
};
$("#my-button").on('click', function(e) {
$.post("/my").done(function(data) {
getProgress(data.next, 5000);
});
e.preventDefault();
});
Caveat emptor: that code is meant to be illustrative, and is missing things you should take care of such as error handling, preventing duplicate submissions, and so forth.