Dcard_2023_backend_intern_homework

Hi, I'm Sun. This is my Dcard's 2023 backend intern homework.

Environment

• Go 1.20
• PostgreSQL 15.2

Installation

1. Set up environment configurations

cp .env.example .env
cp docker-compose.yml.prod.example docker-compose.yml # There are two example files (development and production for different situation)
# edit `.env` and `docker-compose.yml` before continue

2. Create and Start containers

docker-compose up -d

3. Run migrations

Install golang-migrate and run commands below. (install it first)

migrate -database postgres://postgres:{password}@db:5432/postgres?sslmode=disable -source file://migrations up # change the password here
# and run for testing database
migrate -database postgres://postgres:{password}@db:5432/testing?sslmode=disable -source file://migrations up # change the password here

Done! the application is running!

Testing

1. change .env file from:

...
DB_DATABASE=postgres
...

to:

...
DB_DATABASE=testing
...

2. enter the container go, and run test

go test -p 1 -count 1 ./...

APIs

POST /head

request

{
    "key": "head1"
}

response

http status: 201

POST /node

request

{
    "key": "node1",
    "value": "content",
    "prev": "head1"
}

response

http status: 201

GET /head/:key

Get head by key.

response

{
    "key": "head1",
    "next": "node1",
    "created_at": "2023-04-05T14:20:59.206051Z",
    "updated_at": "2023-04-05T14:20:59.206051Z"
}

GET /node/:key

Get node by key.

response

{
    "key": "node1",
    "value": "some content",
    "next": "node2",
    "created_at": "2023-04-05T14:01:43.666822Z",
    "updated_at": "2023-04-05T14:01:43.666822Z"
}

DELETE /head/:key

response

http status: 204

DELETE /node/:key

response

http status: 204

Why PostgreSQL?

Why use PostgreSQL for this key-value system?

First. Because in the system, the two neighboring nodes are linked together. So we can benefit from the cascade feature in relational database. For example, if there are nodes like:

NodeA -> NodeB -> NodeC

When we delete NodeC, we need to update NodeB's link after deletion successful. But we have linked two node in our database. So we can do it by simply set cascade as set null on delete.

Second. Because the structure of the table is fixed. We can use the same schema to finish this system.

Base on the reason above, I choose the relational database. And I want to use PostgreSQL instead of MySQL (or other relational db) at this time because it has more feature than MySQL (although not used this time). So I thought it's a good idea to give it a try on a simple project.

Some TODOs

There are some more features I plan to do, but there is no time QQ

• Use migration
• Refactor with DI
• Add a reverse proxy in front of the application
• More formal API documents
• Automation testing by GitHub Actions
• Package Release by GitHub Actions
• Use gRPC instead of RESTful API
• Stress testing and benchmark