BANCO - A crude bank backend API

FUNCTIONALITY

• Create User in the banco system
  • Each user can create multiple accounts, but accounts must have different currency
  • Only user, authenticated into banco system can manage their accounts(create, list, update, delete - CRUD)
• Transactions - money can be transferred from one user account to other
  • To perform transaction, user must be authenticated into banco system
  • User can only send money from their account
  • Transaction can only take place between accounts of same currency
  • Each transaction is consistent

REQUIREMENTS

• Go
• Docker
  • Postgres
• Make

DB design/architecture

TECHNICAL DETAILS

• Database setup scripts in scripts/db.sh
• SQLC to generate models and crud code
• golang-migrate for migrations
• environment variable setup in makefile (best practice)
• Nice way to implements DB transaction for money transfer
  • transaction lock and deadlock handling while updating user account balances
  • For each transaction
  • transfer details are stored in transfer table(fromAccount, toAccount, amount)
  • Two entries created in entry table, how much money got added/deducted from toAccount and fromAccount
  • Update account balance of fromAccount and toAccount
• Testing
  • Unit tests
  • Integration tests
  • testing via mocking (dependency injection - db layer is injected into api layer)
  • go-mockery is used for mocking
  • Test containers are used to run integration tests
  • There is no service layer, as it seems to be a little overkill for this project.
• In api request - custom param validator (used reflection)
• User password encryption using bcrypt
• Use Paseto based user authentication
  • JWT authentication code is also present
  • Interface is used for Token based authentication
  • So, you can easily replace Paseto with JWT
• Github Actions is used as Pipeline
• Docker and docker compose setup
• Pushing latest images to digital oceans private registery on push

SETUP

Export variables

  export POSTGRES_USER=postgres
  export POSTGRES_PASSWORD=anything
  export DB_HOST=localhost # for local setup
  export DB_HOST=host.docker.internal # for docker setup
  export TOKEN_SYMMETRIC_KEY=blahblahblahblahblahblahblahblah # 32 in length

local setup

• bancoadmin and bancodb is defined in app.env

  make run-postgres
  make create-db
  make server

Run Migrations

• Migrations are run by default when app restarts
• But, if you want to run migrations from cli, POSTGRES_URL variables must be exported

export POSTGRESQL_URL='postgres://${POSTGRES_USER}:{$POSTGRES_PASSWORD}@localhost:5432/bancodb?sslmode=disable'
cli-migrate-up

Run tests

make test

Docker setup

  export DB_HOST=host.docker.internal
  make run-postgres
  docker network create banco
  docker network  connect banco postgres-banco
  docker build -t banco .
  docker run --name banco -p 8080:8080 --network banco -e DB_USER=${POSTGRES_USER} -e POSTGRES_PASSWORD=${POSTGRES_PASSWORD} -e TOKEN_SYMMETRIC_KEY=${TOKEN_SYMMETRIC_KEY} -e DB_HOST=${DB_HOST} -e GIN_MODE=release banco

Docker compose setup

export DB_HOST=host.docker.internal

• If you want to run any command line snippets for docker compose setup, use concept of start.sh. more details

• All the above instructions can be bundled together into makefile target or some script, but I like it this way as it will become very easier to debug if you know what is happening under the hood.

Use API

• Export the below collection in postman or thunder-client(vscode)
• After create-user, run user user-login to get the token to perform any other api action API Collection