Onion Architecture Boilerplate

DESCRIPTION

This repository is a real life example of Onion Architecture with use of Node.js / Express and Typescript

Diagram available here

Diagrams have copyrights, if you want to use it on larger scale, feel free to contact me.

BUSINESS CONTEXT

Project is a simple simulator of warehouse and managing storage space. There are two separate perspectives Administrative and Client facing app.

User Stories

Portal - Client facing app

Given that I'm not a Client
And I would like to create account
When I provide required data
Then my account is created

Given I'm not authenticated Client 
And I would like to authenticate
When I provide proper authentication details
Then I'm able to get into system

Given I'm authenticated Client 
And I would like to delete account
When I perform delete action
Then I'm no longer able to authenticate

Given I'm authenticated Client
When I get into my profile
Then I can see my account data

Given I'm authenticated Client
And I would like to create equipment
When I provide all required data
Then Equipment is created

Given I'm authenticated Client
And I have equipment
When I select Warehouse
Then I receive price preview

Given I'm authenticated Client
And I have multiple equipment items
Then I can preview it

Given I'm authenticated Client
Then I can preview available Warehouses

Given I'm authenticated Client
And I have equipment
When I select Warehouse
And perform store item action
Then I receive Warehouse Item with cost included

Administration - Admin facing app

Given I'm authenticated Admin
Then I can preview all equipment
And Users related to equipment

Given I'm authenticated Admin
And I would like to create equipment
When I provide required data
Then Equipment is created

Given I'm authenticated Admin
Then I can preview all warehouses
And related Warehouse Items

Given I'm authenticated Admin
Then I can preview specific warehouse
And related Warehouse Items

Given I'm authenticated Admin
And I would like to create new Warehouse
When I provide all required data with State
Then Warehouse is created

Given I'm authenticated Admin
And there is existing Warehouse
When I provide new data with State
Then Warehouse data is updated

Given I'm authenticated Admin
And there is existing WarehouseItem
Then I can preview it

Given I'm authenticated Admin
And there are many existing WarehouseItems
Then I can preview all of them

Given I'm authenticated Admin
And I would like to create new WarehouseItem
When I provide all required data with Warehouse
Then WarehouseItem is created

Given I'm authenticated Admin
And there is existing WarehouseItem
When I provide new data with Warehouse
Then WarehouseItem is updated

Given I'm authenticated Admin
Then I can preview all Users

Given I'm authenticated Admin
Then I can preview all States
And related Rates

Given I'm authenticated Admin
Then I can preview all Rates

TECHNICAL ASPECT

Technologies used

1. Typescript ( v3.7.5 )
2. Inversify.js
3. TypeOrm
4. Express.js
5. Apollo Server
6. GraphQL
7. Mocha / Chai for testing

Structure

1. core ( Application Core )

    Contains application core related layers like application services, domain and domain services
   

2. dependency ( Dependency injection layer )

    Contains definition for Container and whole project dependencies
   

3. infrastructure

    Contains definition of data sources in case of this boilerplate - database
   

4. ui

    Contains definition of presentation layer like controller, express setup etc  
   

Data flow

It's important to keep data flow as simple as possible. Generally it's simple to follow - for entry data always specify request object, for output translate data to specific layer. For easier understanding I've prepared a diagram.

Diagram available here

Architecture layers access restrictions

Every layer has its own rules when it comes to access to another layer.

• Dependency injection has access to every layer to provide proper implementations.
• UI have access only to Core Layer
  • Domains can be grouped into Bounded Context
  • Given Domains do not see each other, but defines protocol of communication like CLI, REST etc.
• Infrastructure have access only to Core Layer
  • Functionalities can be grouped into Functionality Group like Messaging, Persistence etc
  • Given Functionalities do not see each other, but have access to Data Source
• Core Layer don`t have access to any layer. It means that it's fully independent of implementations and can be extracted from project if needed
  • Application Service here have access to Domain Services and Domain Models
  • Domain Serivce have access only to domain models, and Domain Services don`t see one each other
  • Domain Model don`t have access to any upper layer

Visual representation of above restrictions can be seen in a diagram.

Diagram available here

Architecture layers in details

To understand in details how whole architecture works together with applied design patterns etc take a look at detailed diagrams per layer.

Diagram available here

Diagram available here

Diagram available here

Architecture Growth Lifecycle

It's natural that every project evolve with time. From my perspective process of growth can be divided into specific phases.

• Initial Phase
  • Introducing Onion Architecture to project by layering codebase - separating code into UI, CORE, INFRASTRUCTURE layers
• Bounded Context Phase
  • Grouping domains into Bounded Contexts
• Bounded Context Growth Phase
  • Separating whole project into Multiple Bounded Contexts
• Modularization Phase
  • Dividing Project into Modules. Usually you will notice that you can rollback your code to Initial Phase as modules are separation was based on Bounded Contexts
• Modularization Growth Phase
  • Every Module evolve in its own pace up to Bounded Context Growth Phase. You may have also Common Module which is shared across other modules.
• Microservices Phase
  • After some time you may notice that having multiple modules within one codebase is too much, or you may se that specific module is a potential candidate to Microservice. If you decide to detach Module into Microservice you may start application lifecycle from the beginning or from any phase you like up to Modularization Growth Phase. You may even start from initial phase and move through all the phases within specific Microservice. Every Microservice Architecture lifecycle is independent ( like in Modularization Growth Phase)

Visual representation of above process can be seen in a diagram.

Diagram available here

Database Structure

To have better context on general example of architecture, it's also good to understand database structure and how whole project structure is aligned to it.

What is supported?

1. Multiple environment setup
2. DB Agnostic setup, supports multiple datasource
3. Infrastructure -> Domain Mapping -> UI Mapping
4. Migrations, Fixtures, Seeds
5. Multiple API versions support ( REST implementation )
6. Global Error Handling
7. Test Parallelization
8. Multiple protocols within one codebase ( GraphQL / REST )

Reference

Inspired by following articles:

https://dev.to/remojansen/implementing-the-onion-architecture-in-nodejs-with-typescript-and-inversifyjs-10ad

https://herbertograca.com/2017/11/16/explicit-architecture-01-ddd-hexagonal-onion-clean-cqrs-how-i-put-it-all-together

https://www.slideshare.net/matthidinger/onion-architecture

PREREQUISITIES

• Yarn

• NVM ( tested on v10.13.0+)

  wget -qO- https://raw.githubusercontent.com/nvm-sh/nvm/v0.34.0/install.sh | bash`
  

• PostgreSQL ( tested on v11+)

SETUP

1. Database
   • Look at the ormconfig.sample.js file. It's a sample setup of database connection, you can provide your own data for database if needed. From app perspective you have to manually create a database for development ( in sample with name onion_dev ) and for testing onion_test.
   • Migrations will autorun on application start
2. Env Variables

   • .env.example contains example env config - for local / dev use you can use same values as provided in sample

   • for production use generate token with following command

       node -e "console.log(require('crypto').randomBytes(256).toString('base64'));"   
     

HOW TO RUN LOCALLY

1. Follow SETUP section first and install PREREQUISITIES
2. Yarn install - installing dependencies
3. Yarn dev - run app with watch and rebuild

WORKING WITH DATABASE

1. To prepare a database with the latest migrations run yarn db:reload, it also removes all data from db and recreates it. Useful when playing with seed data.
2. To seed database run yarn db:seed
3. To generate migration based on changes in entity object run yarn db:generate <my_migration_name>

SWAGGER

When there is a swagger host provided in .env file then you can navigate to http://localhost:3000/api-docs/

Update swagger.json file located at ui > config every time you apply changes to api.

GRAPHQL PLAYGROUND

Navigate to http://localhost:3000/graphql to make queries through GraphQL playground

TESTING

1. Prepare tests database first ( SETUP SECTION )
2. Run yarn test - should run mocha tests in parallel

Mutational Testing

1. Read guide here to setup global dependencies
2. Run yarn test:mutate command

APPLIED CONCEPTS

There are some universal concepts in programming ( designed patterns ) which are common for general engineering, but it's not always obvious how to use environment specific concepts. In this boilerplate I'm going to show how to handle that.

Request Object

Request object defines parameters / input to specific module input ( domain / infrastructure ), and holds required data which cannot be changed on the fly.

Unit Of Work

Unit Of Work is simply speaking - a wrapper. It wraps repositories and performs required operations usually in transaction. It solves issue related to circular repository dependency in ioc, or nested repository dependency on each other. With unit of work specific repository methods don't have any reference to external repositories which makes them more atomic.

Interactor / UseCase / Scenario

Interactor is a single, independent action to execute in any place of the system. It contains logic related to specific problem ( usually also to specific domain ) and can be shared across multiple domains. It has clear input definition and output. The idea of interactor is to avoid need of nesting services in each other. If you need to nest services then you also combine domains, and you will face cross domain issues. As interactor is independent operation to reuse, it CANNOT have service as dependency ( repository is allowed ). It can be injected into service though.

UseCase you can see it as a wrapper, if you have business use case which depends on multiple interactor results, and you need to apply some logic on those results, then UseCase is a way to go. UseCase may have multiple interactors as dependencies + repositories.

Scenario is a wrapper around UseCases. Same way of thinking as in UseCase - if you have a complex, reusable across multiple domains / modules operation, which depends on multiple UseCases, Interactors, repositories results, and you need to apply specific logic on those results, then scenario is a way to go.

All of those concepts should be presented as single action to execute - there shouldn't be multiple methods / functions applied to their interfaces, just execute.

Mapper

The Simple concept, where one module data structure is translated to another module

Infrastructure -> Domain Mapper

This mapper is prepared for mapping data source format data into domain format. The Simplest example would be that, in a database we store first_name and last_name in separate columns, but in a domain we need to have field name which is combined value of previously mentioned columns. In that case we define domain model with required fields and new name field. In a Mapper, we can perform merging of those 2 values. Thanks to that we can have separation between definition of Entity and Domain, and also we have just plain values in domain object instance without any overhead related to persistence data etc, which for sure would be stored by Entity object instance. We can also calculate simple values in mappers etc.

Domain -> UI Mapper

This mapper is for preparing Domain data format into specific ui data format. Sometimes we may need to perform some logic in domain services on domain object format, but we would like to make a response in totally different format. For example, we may fetch data as array from a database, perform operations in services on an array but on UI, we would like to group array elements into map structure in a different format. In a repository, we mapped User domain object into User ui object where UI object do not contain password field and contains only required fields for authentication purposes.

Migrations

Used for managing database changes. In a repository, we generate migrations based on entity changes. So we can add a new column on entity and then just use one command to generate required migration. It's recommended to split database related changes into multiple migrations instead creating one migration for all related feature changes. For example, it's better to have separate migration for creating x table and separate migration for adding / updating table columns definition to table y.

Seeds

Used for local development or testing - it's just data for specific use cases which can be also used for dev environment where QA's can test specific endpoints or screens. It's also useful as start data for local development especially when you are working as a full stack.

Tests parallelization

Every test runs on it's separate database, and we can spawn multiple tests at the same time, and run in transaction specific test cases, thanks to which we don't have to clear db after running every test.

Mutational testing

Mutational testing is integrated with Mocha test runner and shows how many mutations are still available in system, and where we should apply additional test coverage.

Integration testing

We are testing whole layers data flow - from UI layer up to Infrastructure. We are testing not only responses but also saved data in database and authentication context.

STILL TODO

• Prepare FP version of architecture - separate repo
• Introduce the Docker into project
• Prepare testing infrastructure for GraphQL endpoints, add more tests, update testing and fix issues
• Provide example of project modularization ( lerna + yarn workspaces )
• Resolve TODO's comments

KNOWN ISSUES

• To authenticate provide token this way as swagger 2.0 do not support bearer strategy https://github.com/OAI/OpenAPI-Specification/issues/583#issuecomment-267554000

• http context is empty in controllers, looks like http context is incorrectly injected into controller, everything is fine though in middlewares - applied workaround take a look at getCurrentUser helper