/wallet-api

Test assessment task for the job

Primary LanguageGoMIT LicenseMIT

wallet-api

Build Status

Service stores account balances and provide one with functionality of transferring money from one account to another.

Domain

For detailed API documentation see /docs/API.md. You can find DDD like description at code-level in services/transfers/domain.go.

Business assumptions

  • All IDs here are uuid4.
  • Service support multiple currencies each one with precision specified in DB.
  • Term transfer suits better than payment.
  • No functionality for deposit/withdraw - just inner transfer.
  • Each transfer consist of one(deposit/withdraw) or two(inner) parts that are denormalized (for better read performance).
  • Transfer amount rounding without any error if there is extra precision specified.

Business conventions

  • 'USD' and 'usd' means the same, but we use first for inner representation.
  • Transfer operations positive-idempotent(means after succeeded once it will always return 'OK' without duplication).

Tech assumptions

  • Service simplified - there is no prometheus metrics, tracing and extra logging.
  • It's supposed to run in k8s - there is no service discovery logic.
  • For supported configuration flags see ./cmd/api/config.go.
  • When started server tries connect to DB until succeed or retries count exceeded(see configuration options).
  • To stop server gracefully you need to send SIGHUP, and it will try do it in time specified via configuration.

DB layout

DB Schema

Configuration

Usage of /bin/api:
  -db string
    	db connections credentials
  -dbRetryCount uint
    	retry count for connecting to db (default 10)
  -dbRetryTimeout duration
    	retry timeout for connecting to db (default 2s)
  -logLevel string
    	debug|info|warn|error (default "info")
  -port string
    	port (default "8080")
  -shutdownTimeout duration
    	graceful shutdown timeout (default 10s)

Questions and features to be considered for future

  • Separation for booking and spending for 2-phase transactions.
  • Pagination for 'all' methods.
  • Currencies exchange.
  • Deposit/Withdraw from outside world.
  • Additional API methods.

How to run code or develop

Preparations

You need install:

Run locally

task build_dev_tools # builds tooling image
task up # run all in docker compose
# wait some time until PostgreSQL will statred
task migrate # apply migrations inside docker-compose started by task up
task -l # for available tasks for development

Development

Some task commands may require tools that presented in docker image that can build from tools/Dockerfile-tools via task build_dev_tools.

Attaches git hooks for running test/linter in development process lifecycle, also prepending each commit msg with [<branch_name>] prefix for later investigations via git blame.

task attach_hooks

After you start and change something modd rebuild and restart app via ./tools/modd.conf There is also ./integration/init.sql file that maybe useful if you decide to populate DB with test data.

Tests

task test # if have go installed or inside go-dev-tools docker image
task run_integration_tests # runs integration tests via docker-compose

Build Docker image for deployment

Be aware you need to run migrations before image deploy (e.g. via k8s job)

IMAGE_NAME=wallet-api:1.0.0 task build_api_image

Things used

Code

Tools