Taming Monoliths without Microservices - RubyConf AU 2019

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TAMING MONOLITHS WITHOUT MICROSERVICES Kelly Sutton — Rubyconf AU 2019

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Overview I. About Me II. Breaking the Monolith III. Tactics IV. Wrap Up kellysutton.com

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Part I: About Me

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About Me

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About Greta

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About Greta

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About Greta

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About Greta

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But that’s not why we’re here kellysutton.com

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We’re here to talk about Rails projects that push the limits kellysutton.com

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kellysutton.com

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Time Geography Money People kellysutton.com

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Correctness > Performance kellysutton.com

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What goes wrong, when things get too big kellysutton.com

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Part II: Breaking the Monolith

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The Swamp kellysutton.com

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No content

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kellysutton.com

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kellysutton.com

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The Swamp Payroll HR Beneﬁts Infra kellysutton.com

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“Let’s Extract a Service!” kellysutton.com

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Photo by Thomas Halfmann kellysutton.com

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The Swamp Payroll HR Beneﬁts Infra kellysutton.com

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The Swamp Payroll HR Beneﬁts Infra kellysutton.com

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The Swamp Payroll HR Beneﬁts Infra HR v2 kellysutton.com

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The Swamp Payroll HR Beneﬁts Infra HR v2 kellysutton.com

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The Swamp Payroll Old HR Beneﬁts Infra HR v2 kellysutton.com

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But there is a better way

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kellysutton.com

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Employee HR Payroll kellysutton.com

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Employee HR Payroll kellysutton.com

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Employee HR Payroll employee.last_name kellysutton.com

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HR Payroll kellysutton.com

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HR Payroll kellysutton.com

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HR Payroll Employee PayrollEmployee kellysutton.com

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HR Payroll Employee PayrollEmployee kellysutton.com

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HR Payroll Employee PayrollEmployee payroll_employee.last_name kellysutton.com

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HR Payroll kellysutton.com

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HR Payroll kellysutton.com

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Value Objects HR Payroll kellysutton.com

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Conceptual Compression

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Conceptual Expansion

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Part III: Tactics

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Recommendation #1 Mind and Avoid Circular Dependencies kellysutton.com

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As your Rails code base grows, question bidirectional relationships kellysutton.com

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1 # app/models/company.rb 2 class Company < ApplicationRecord 3 has_many :employees 4 end 5 6 # app/models/employee.rb 7 class Employee < ApplicationRecord 8 belongs_to :company 9 end kellysutton.com

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1 # app/models/company.rb 2 class Company < ApplicationRecord 3 has_many :employees 4 end 5 6 # app/models/employee.rb 7 class Employee < ApplicationRecord 8 belongs_to :company 9 end Do we need this? kellysutton.com

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Company Employee kellysutton.com

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Company Employee kellysutton.com

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Recommendation #2 Use Value Objects to Traverse Edges kellysutton.com

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1 # app/services/company_signed_up.rb 2 class CompanySignedUp 3 def self.call(company) 4 CompanyMailer.welcome_email(company) 5 StatsTracker.company_signed_up(company) 6 end 7 end kellysutton.com

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1 # app/services/company_signed_up.rb 2 class CompanySignedUp 3 def self.call(company) 4 user_first_name = company.admin_first_name 5 email = company.admin_email 6 7 CompanyMailer.welcome_email(email, user_first_name) 8 StatsTracker.company_signed_up(company.id) 9 end 10 end kellysutton.com

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Recommendation #3 Avoid Callbacks kellysutton.com

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1 # app/models/company.rb 2 class Company < ApplicationRecord 3 after_create :send_update_email, if: :has_email? 4 5 private 6 7 def send_update_email 8 CompanyMailer.welcome_email(self) 9 end 10 end kellysutton.com

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Company CompanyMailer kellysutton.com

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1 # app/services/create_company.rb 2 class CreateCompany 3 def self.call(company_params) 4 company = Company.create!(company_params) 5 6 CompanyMailer.welcome_email(company) 7 end 8 end kellysutton.com

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Company CompanyMailer CreateCompany kellysutton.com

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Recommendation #4 Move slowly! kellysutton.com

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Part IV: Wrap Up kellysutton.com

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–Kent Beck “Make the hard change easy (this may be hard), then make the easy change.” kellysutton.com

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Thanks! Slides and more available at kellysutton.com

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References • Bernhardt, Gary. “Boundaries.” 2012. • Bernhardt, Gary. “Functional Core, Imperative Shell.” 2012. • Evans, Eric. “Domain-Driven Design: Tackling Complexity in the Heart of Software.” 2003. • Fowler, Martin, et al. “Refactoring: Improving the Design of Existing Code.” 1999. • Feathers, Michael. “Working Eﬀectively with Legacy Code.” 2004. • Hickey, Rich. “Simple Made Easy.” 2011. • Hickey, Rich. “The Value of Values.” 2012. • Scott, James C. “Seeing Like a State.” 1999. • Searls, Justin. “My Preferred Method of TDD.” 2017 • Spolsky, Joel. “Things You Should Never Do, Part I.” 2006.

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Special Thanks • Noa Elad • Matan Zruya • Sihui Huang • Natalie Wong • Karlo Hoa • Amelie Meyer-Robinson • Quentin Balin