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Building an Umbrella Project Wojtek Mach @wojtekmach @wojtekmach

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Me • Ruby • GitHub API adapter for Ecto • OOP library for Elixir • Acme Bank

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Me • Ruby • GitHub API adapter for Ecto • OOP library for Elixir • Acme Bank

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Me • Ruby • GitHub API adapter for Ecto • OOP library for Elixir • Acme Bank

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Me • Ruby • GitHub API adapter for Ecto • OOP library for Elixir • Acme Bank

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What’s an Umbrella Project?

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Inspiration

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Inspiration Architecture: The Lost Years
 Robert C. Martin, Midwest RubyConf 2011
 • Typical Rails app • app/{models,controllers,view} • Top-level architecture should scream it’s intent

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Inspiration Architecture: The Lost Years
 Robert C. Martin, Midwest RubyConf 2011
 • Typical Rails app • app/{models,controllers,view} • Top-level architecture should scream it’s intent

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Inspiration Architecture: The Lost Years
 Robert C. Martin, Midwest RubyConf 2011
 • Typical Rails app • app/{models,controllers,views,…} • Top-level architecture should scream it’s intent

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Inspiration Architecture: The Lost Years
 Robert C. Martin, Midwest RubyConf 2011
 • Typical Rails app • app/{models,controllers,views,…} • Top-level architecture should scream it’s intent

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Inspiration Wrangling Large Rails Codebases
 Stephan Hagemann, Rocky Mountain Ruby 2012
 • Advice about writing large apps • Components

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Inspiration Wrangling Large Rails Codebases
 Stephan Hagemann, Rocky Mountain Ruby 2012
 • Advice about writing a large app • Components

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Inspiration Wrangling Large Rails Codebases
 Stephan Hagemann, Rocky Mountain Ruby 2012
 • Don’t write a large app • Components

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Inspiration Wrangling Large Rails Codebases
 Stephan Hagemann, Rocky Mountain Ruby 2012
 • Don’t write a large app • Components: gems & engines

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Inspiration The Art of Destroying Software
 Greg Young, Leetspeek 2014 
 • organize your project in a way that makes it easy to delete code.

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Inspiration The Art of Destroying Software
 Greg Young, Leetspeek 2014 
 • organize your project in a way that makes it easy to delete code.

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What’s an Umbrella Project?

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What’s an Umbrella Project? • Mixfile • apps/ directory • OTP applications

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OTP application „In Elixir (actually, in Erlang/OTP), an application is a component implementing some specific functionality, that can be started and stopped as a unit, and which can be re-used in other systems.” — Elixir API docs

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OTP application • application dependencies • configuration • start/stop behaviour • regular applications & library applications

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OTP application • application dependencies • configuration: config.exs, Application.put_env, mix.exs • start/stop behaviour • regular applications & library applications

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OTP application • application dependencies • configuration • start/stop behaviour • regular applications & library applications

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OTP application • application dependencies • configuration • start/stop behaviour • regular applications & library applications

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OTP application • application dependencies • configuration • start/stop behaviour • regular applications & library applications • standard

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OTP application „Application”

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OTP application Server

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OTP application Service

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OTP application Microservice

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Building Acme Bank

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$ mix new bank_platform --umbrella

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# mix.exs defmodule BankPlatform.Mixfile do use Mix.Project def project do [apps_path: "apps", deps: deps(), aliases: aliases()] end end Bank Platform

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First OTP App

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Bank

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$ cd apps/
 $ mix new bank --sup Bank

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# apps/bank/mix.exs defmodule Bank.Mixfile do use Mix.Project def project do [app: :bank, version: "0.1.0", build_path: "../../_build", config_path: "../../config/config.exs", deps_path: "../../deps", lockfile: "../../mix.lock", deps: deps()] end end Bank

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First Feature

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First Feature: Account Balance

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defmodule Bank.Account do defstruct name: "", balance: 0 end Naive

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defmodule Bank.Account do defstruct name: "", balance: 0 def deposit(account, amount) do %Account{account | balance: account.balance + amount} end end Naive

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Accounting 101

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Accounting 101 • Any movement of money happens between at least 2 accounts: one account is debited and the other account is credited • Example: Alice transfers $100 to Bob

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Accounting 101 • Any movement of money happens between at least 2 accounts: one account is debited and the other account is credited • Example: Alice transfers $100 to Bob

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Alice transfers $100 to Bob | Bob | :credit | 100.00 | Alice | :debit | 100.00 Accounting 101

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Bob transfers $20 to Alice | Bob | :credit | 100.00 | Alice | :debit | 100.00 | Alice | :credit | 20.00 | Bob | :debit | 20.00 Accounting 101

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Bob transfers $10 to Alice | Bob | :credit | 100.00 | Alice | :debit | 100.00 | Alice | :credit | 20.00 | Bob | :debit | 20.00 | Bob | :debit | 10.00 | Alice | :credit | 10.00 Accounting 101

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Bob’s balance = $100 - $20 - $10 = $70 | Bob | :credit | 100.00 | Alice | :debit | 100.00 | Alice | :credit | 20.00 | Bob | :debit | 20.00 | Bob | :debit | 10.00 | Alice | :credit | 10.00 Accounting 101

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Bob’s balance = $100 - $20 - $10 = $70 | Bob | :credit | 100.00 | Alice | :debit | 100.00 | Alice | :credit | 20.00 | Bob | :debit | 20.00 | Bob | :debit | 10.00 | Alice | :credit | 10.00 Accounting 101

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Alice’s balance = -$100 + $20 + $10 = -$70 | Bob | :credit | 100.00 | Alice | :debit | 100.00 | Alice | :credit | 20.00 | Bob | :debit | 20.00 | Bob | :debit | 10.00 | Alice | :credit | 10.00 Accounting 101

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Alice’s balance = -$100 + $20 + $10 = -$70 | Bob | :credit | 100.00 | Alice | :debit | 100.00 | Alice | :credit | 20.00 | Bob | :debit | 20.00 | Bob | :debit | 10.00 | Alice | :credit | 10.00 Double-entry accounting system Accounting 101

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Accounting 101 Why mention this? • it’s a Bank • it’s functional • mathematical properties • complexity

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Accounting 101 Why mention this? • it’s functional • mathematical properties • complexity

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Accounting 101 Why mention this? • it’s functional • mathematical properties • complexity

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Accounting 101 Why mention this? • it’s functional • associativity • complexity

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Accounting 101 Why mention this? • it’s functional • associativity, commutativity • complexity

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Accounting 101 Why mention this? • it’s functional • associativity, commutativity, idempotence • complexity

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Accounting 101 Why mention this? • it’s functional • CRDT • complexity

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Accounting 101 Why mention this? • it’s functional • eventual consistency [1] • complexity [1] http://highscalability.com/blog/2013/5/1/myth-eric-brewer-on-why-banks-are-base-not-acid-availability.html

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Accounting 101 Why mention this? • it’s functional • eventual consistency [1] • complexity [1] http://highscalability.com/blog/2013/5/1/myth-eric-brewer-on-why-banks-are-base-not-acid-availability.html

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Accounting 101 Why mention this? • it’s functional • eventual consistency [1] • complexity • complexity [1] http://highscalability.com/blog/2013/5/1/myth-eric-brewer-on-why-banks-are-base-not-acid-availability.html

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Bank: Entities

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Bank: Entities • Account • Entry • Customer

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Bank: Entities • Account: web/models/account.ex • Entry: web/models/entry.ex • Customer: web/models/customer.ex

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Bank: Entities • Account: lib/bank/account.ex • Entry: lib/bank/entry.ex • Customer: lib/bank/customer.ex

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Bank: Entities • Account: lib/bank/account.ex • Entry: lib/bank/entry.ex • Customer: lib/bank/customer.ex Different rates of change

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Bank: Entities • Account: lib/bank/ledger/account.ex • Entry: lib/bank/ledger/entry.ex • Customer: lib/bank/customer.ex Different rates of change

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Bank: Persistence

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Bank: Persistence • Ecto • Where to put Repo access?

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Bank: Persistence • Ecto • Where to put Repo access?

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Bank.Ledger # lib/bank/ledger.ex defmodule Bank.Ledger do def balance(account) do Repo.one("SELECT SUM(...)") end def write(entries) do # ... end end

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Bank.Ledger # lib/bank/ledger.ex defmodule Bank.Ledger do def balance(account) do Repo.one("SELECT SUM(...)") end def write(entries) do # ... end end

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Bank.Ledger # lib/bank/ledger.ex defmodule Bank.Ledger do def balance(account) do Repo.one("SELECT SUM(...)") end def write(entries) do # ... end end

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Bank # lib/bank.ex defmodule Bank do def create_customer(params) do Bank.Customer.changeset(params) |> Repo.insert end end

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Bank # lib/bank.ex defmodule Bank do def create_customer(params) do Bank.Customer.changeset(params) |> Repo.insert end end

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Bank # lib/bank.ex defmodule Bank do def create_customer(params) do Bank.Customer.changeset(params) |> Repo.insert end end

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Bank Bank.create_customer/1
 Bank.Ledger.balance/1
 Bank.Ledger.write/1 • Use cases • Use in controllers, tests, iex, seeds

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Bank Bank.create_customer/1
 Bank.Ledger.balance/1
 Bank.Ledger.write/1 • Use cases • Use in controllers, tests, iex, seeds

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Bank Bank.create_customer/1
 Bank.Ledger.balance/1
 Bank.Ledger.write/1 • Use cases • Use in controllers, tests, iex, seeds

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Money

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Money • Amount + currency • Operations • Persistence • Isolation • OSS • Productivity

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Money • Amount + currency • Operations • Persistence • Isolation • OSS • Productivity

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Money • Amount + currency • Operations • Persistence • Isolation • OSS • Productivity

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Money • Amount + currency • Operations • Persistence • Isolation • OSS • Productivity

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Money • Amount + currency • Operations • Persistence • Isolation • OSS • Productivity

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Money • Amount + currency • Operations • Persistence • Isolation • OSS • Productivity

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Money # apps/bank/mix.exs defp deps do [ {:money, in_umbrella: true} ] end

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Money # apps/bank/mix.exs def application do [applications: [..., :money]] end

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BankWeb

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BankWeb $ cd apps/ $ mix phoenix.new bank_web # add bank as dependency

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BankWeb $ cd apps/ $ mix phoenix.new bank_web # add bank as dependency

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BankWeb $ cd apps/ $ mix phoenix.new bank_web # add bank as dependency

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BankWeb • boring! • connect controllers to business logic

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BankWeb • boring! • separation of concerns

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Backoffice

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Backoffice • ExAdmin. Works with umbrellas out of the box • ports setup • deployment • Phoenix is Not Your Application

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Backoffice • ExAdmin. Works with umbrellas out of the box • setup different ports in development • deployment • Phoenix is Not Your Application

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Backoffice • ExAdmin. Works with umbrellas out of the box • setup different ports in development • deployment • Phoenix is Not Your Application

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Backoffice • ExAdmin. Works with umbrellas out of the box • setup different ports in development • deployment • Phoenix is Not Your Application

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Backoffice • ExAdmin. Works with umbrellas out of the box • setup different ports in development • deployment • Phoenix is Not Your Application

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Deployment

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Deployment • Heroku • MasterProxy.

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Deployment • Heroku • MasterProxy.

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Deployment • Heroku • MasterProxy. Thanks @TheGazler! • distillery, exrm replacement, has 1st class support for umbrellas

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Deployment • Heroku • MasterProxy. Thanks @TheGazler! • distillery, exrm replacement, has 1st class support for umbrellas

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Auth

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Auth • Upfront design? • Features: audit logs

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Auth • Upfront design? • Features: strategies

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Auth • Upfront design? • Features: strategies, 2FA

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Auth • Upfront design? • Features: strategies, 2FA, tracking

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Auth • Upfront design? • Features: strategies, 2FA, tracking

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Auth • Upfront design? • Features: strategies, 2FA, tracking • Separate Repo, separate DB

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Auth • Upfront design? • Features: strategies, 2FA, tracking • Separate Repo, separate DB • Thanks @chris_mccord!

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Messenger

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Bank Platform

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BankPlatform • auth • bank • bank_web • backoffice • master_proxy • messenger • money

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BankPlatform

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BankPlatform

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BankPlatform

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Microservices

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Microservices Benefits: • Strong Module Boundaries • Independent Deployments • Technology Diversity http://martinfowler.com/articles/microservice-trade-offs.html

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Microservices Benefits: • Strong Module Boundaries • Independent Deployments • Technology Diversity http://martinfowler.com/articles/microservice-trade-offs.html Drawbacks: • Distribution • Eventual Consistency • Operational Complexity

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Conclusion

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Conclusion • keep an eye on the big picture

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Conclusion • keep an eye on the big picture • don’t write a large app

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Conclusion • keep an eye on the big picture • don’t write a large app • isolate by functionality and rate of change

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Conclusion • keep an eye on the big picture • don’t write a large app • isolate by functionality and rate of change • delete code liberally

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Thanks! wojtekmach/acme_bank