How should Sidekiq notify user on the web page when job is finished?

Add a RecordJobs model to your application that stores who uploaded the records, the number of records, the upload time and so on.

Create a new record_job each time someone uploads new records and pass its id to the worker. The worker can update that instance to indicate its progress.

At the same time, the application can query for existing record_job and show their progress. That can be done whenever the user reloads it page, by active polling or with web sockets (depending on your needs).

use ActionCable, here is the example with Report channel

In routes.rb add the following line

mount ActionCable.server => '/cable'

create a ReportChannel.rb inside app/channels with following code

class ReportChannel < ApplicationCable::Channel
  def subscribed 
    stream_from "report_#{current_user.id}"
  end
end

create reports.coffee inside app/assets/javascripts/channels with the following code

  window.App.Channels ||= {}
  window.App.Channels.Report ||= {}
  window.App.Channels.Report.subscribe = ->
      App.report = App.cable.subscriptions.create "ReportChannel",
        connected: ->
          console.log('connected ')

        disconnected: ->
          console.log('diconnected ')

        received: (data) ->
          console.log('returned ')
          data = $.parseJSON(data)
          #write your code here to update or notify user#

and add the following lines at the end of your job

ActionCable.server.broadcast("*report_*#{current_user_id}", data_in_json_format) 

replace report with your specific model

seems simple right :)