Do not belittle rake tasks

Transcript

1. Do Not Belittle Rake Tasks
   Mateusz Bielec
   RRUG #16, 06.11.2018
   

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2. What is a rake task?
   ● Just a script to run at any time in a console
   ● Common Rails tasks:
   ○ rake db:reset, rake db:create, rake db:migrate
   ○ rake -T
   ○ rake routes
   ● Custom task:
   desc 'Rake task description'
   task :name_of_task do
   # Your code goes here
   end
   

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3. When we use custom rake tasks?
   ● Script automation
   ● Data cleanup
   ● Long database migration
   

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4. Why is it important to write a good custom rake
   task?
   ● Usually it’s production code
   ● Readability
   ● Maintainability
   ● Testing
   ● Transparency
   

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5. https://memegenerator.net/img/instances/82302636/brace-yourself-opinions-are-coming.j
   pg
   

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6. My list of the things to consider
   ● Size of .rake file
   ● Idempotency
   ● Tracking progress
   ● Logging the work
   ● Isolated structure
   ● Testing
   ● The performance
   

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7. * without the boilerplate
   

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8. Ideal .rake file
   namespace :mailchimp
   desc 'Import users from Mailchimp'
   task import_users: :environment do
   Mailchimp::ImportUsers.call
   end
   end
   

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9. Keep .rake file as small as possible
   namespace :mailchimp
   desc 'Import users from Mailchimp'
   task :import_users do
   puts 'Importing users from Mailchimp'
   result = Mailchimp::ImportUsers.call
   puts "Successfully imported #{result} users!"
   end
   end
   

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10. https://memegenerator.net/img/instances/82298063/ive-run-my-rake-task-twice-now-they-call-me-spammer.jpg
    

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11. Idempotency
    ● It’s important on cleanups and migrations
    ● Can be easily fulfilled with:
    ○ a good query
    ○ modifying the input file
    ○ omitting already created data
    

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12. https://memegenerator.net/img/instances/82305346/is-it-started-or-is-it-finished.jpg
    

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13. Tracking progress
    ● The task executor needs to know the current status of the task
    ● Show anything
    ○ from dots
    ○ to printing a line for each processed item
    ● Or use a gem ProgressBar:
    

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14. ProgressBar gem
    namespace :cleanup
    desc 'Cleanup bad fees'
    task :fix_bad_fees do
    query = Cleanup::FixBadFees::Query.call
    progress_bar = ProgressBar.create(
    title: 'Fixing bad fees by adding a discount',
    total: query.count
    )
    # ...
    end
    end
    namespace :cleanup
    desc 'Cleanup bad fees'
    task :fix_bad_fees do
    # ...
    result = Cleanup::FixBadFees::Task.call(query: query) do
    progress_bar.increment
    end
    puts "Successfully fixed #{result} fees!"
    end
    end
    

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15. ProgressBar gem
    class Cleanup::FixBadFees::Task
    def self.call(*args, &block)
    new.self(*args, &block)
    end
    def call(query:)
    query.find_each do
    # Fix bad fees
    yield if block_given?
    end
    end
    end
    

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16. https://memegenerator.net/img/instances/82305371/one-does-not-simply-know-what-happened.jpg
    

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17. Logging
    ● Who performed the task? When? Why?
    ● Log the action
    ○ Notes
    ○ Audit trail
    ○ History events
    ● Log the task’s execution
    ● Include the executor
    ○ TASK_EXECUTOR=jon.snow@westeros rake kill_undead
    

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18. https://memegenerator.net/instance/82305394/all-the-things-put-everything-inside-the-same-directory
    

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19. Isolated structure
    ● .rake files usually in /lib/tasks
    ● The rest in /app/tasks
    ● Each task in a separated module
    

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20. https://memegenerator.net/img/instances/82298452/i-dont-always-test-my-custom-rake-task-but-when-i-do-i-do-it-in-production.jpg
    

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21. Testing custom rake tasks
    ● Automated tests class for each PORO
    class used in a rake task
    ● No automated tests for .rake file, rely on
    manual testing
    ● Don’t be lazy
    

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22. https://memegenerator.net/img/instances/82305309/hmmmm-to-jebie.jpg
    

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23. Performance
    ● Predict the scale at the very beginning
    ● Define bottlenecks
    ○ Reading from large file or from multiple database tables
    ○ Calling external services
    ○ Saving many rows to the database
    ● Use database close to production (locally, staging)
    

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24. Summary
    ● Rake task are a part of our application
    ● Bad task may cause a lot of damage
    ● With a little of effort we can do it right
    

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25. https://memegenerator.net/img/instances/82305270/questions.jpg
    

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