grpc-service-user

This is a small basic grpc service for managing user data stored in postgres database.

Building and Running Project

This project compiles to a binary that runs two different commands:

• server command to start the grpc server, and
• e2e command to run e2e basic tests.

You don't have to compile the binary manually as the project ships a Makefile which automate all the building and testing with docker-compose environment:

# to run unit tests:
make test

# to run e2e tests:
make test-e2e

# to lint project:
make lint

# to build a naked binary:
make build

# to generate protobuf files:
make generate

# to run project in a docker-compose env:
make composer-up

GRPC Endpoints:

The following endpoint are implemented:

+-----------+-------------+--------------------+------------------+
|  SERVICE  |     RPC     |    REQUEST TYPE    |  RESPONSE TYPE   |
+-----------+-------------+--------------------+------------------+
| UserStore | CheckHealth | CheckHealthRequest | CheckHealthReply |
| UserStore | AddUser     | AddUserRequest     | AddUserReply     |
| UserStore | UpdateUser  | UpdateUserRequest  | UpdateUserReply  |
| UserStore | DeleteUser  | DeleteUserRequest  | DeleteUserReply  |
| UserStore | ListUsers   | ListUsersRequest   | User             |
+-----------+-------------+--------------------+------------------+

Refer to api/user.proto for more details about the endpoints and the requests and replies structures.

Server Configurations

The server expects configurations via env vars. The following golang struct explains all the expected environment vars:

type envVars struct {
    Port int `env:"PORT" envDefault:"8080"`
	PostgresHost     string `env:"POSTGRES_HOST" envDefault:"postgres"`
	PostgresPort     int    `env:"POSTGRES_PORT" envDefault:"5432"`
	PostgresUser     string `env:"POSTGRES_USER" envDefault:"admin"`
	PostgresPassword string `env:"POSTGRES_PASSWORD" envDefault:"password"`
	PostgresDB       string `env:"POSTGRES_DB" envDefault:"userdb"`

	NotifierWebHooks []string `env:"NOTIFIER_WEBHOOKS" envSeparator:","`
}

NOTIFIER_WEBHOOKS is a comma seperated string for all web hooks urls used to notify other systems upon user data changes.

Design

1. Storing User Data

I decided to use postgres to store the user data. Postgres is pretty much a good choice for such a use case. I used gorm library to simplify the data access layer code. I never used this lib before but wanted to give it a try.

2. Providing API to do CRUD

Only two options to choose from (rest and grpc). Typically, I would use rest for use case unless wire efficiency and latency is crucial. Here, I used grpc just to be cool :).

3. Pagination and Filtering Endpoint

This feature is implemented via UserStore.ListUsers endpoint. Nothing special to design here. Example call:

# using grpcurl tool:
grpcurl -plaintext -d '{"page": 2, "page_size": 6, "filters": {"email": "me@example.com"}  }'  localhost:8080  api.UserStore.ListUsers

##$ 2. Asynchronous Notification Mechanism

To allow other services getting notified when changes to use data happens, I decided to implement web hook for that. A comma seperated string of webhooks should be configured via NOTIFIER_WEBHOOKS. The server will fire post requests asynchronously. These requests encode both the changed user data (via request body) and the type of the change (via /add /delete /update) paths.

For simplicity, I used a very simple channel + single goroutine to implement a FIFO queue to queue the notifications to be sent asynchronously. For larger and more serious systems, an auto-scaling jobs queue with more goroutines need to be implemented.