Microservices with Golang

Table of Contents.

• Introduction
• Architecture
• Getting Started
  • Prerequisites
  • Installation
  • Running the Services
• Services
  • API Gateway
  • Authentication Service
  • Logger Service
  • Mailer Service
  • Listener Service
  • Payment Service
• Technologies Used
• Contributing
• License

Introduction

This repository contains a microservices-based application built with Golang. The application demonstrates how to use microservices to create a scalable and maintainable architecture. It includes services for authentication, logging, mailing, and a listener service that processes events from RabbitMQ.

Architecture

The architecture is composed of multiple services that communicate with each other through REST APIs and message queues. The services are:

• API Gateway: The entry point for all client requests.
• Authentication Service: Handles user authentication.
• Logger Service: Page application events.
• Mailer Service: Sends emails.
• Listener Service: Listens for events from RabbitMQ and processes them.
• Payment Service: Listens for gRPC calls from api-gateway to Process payments using credit card.

Getting Started

Prerequisites

Before you begin, ensure you have the following installed:

• Golang
• Docker
• Docker Compose

Installation

1. Clone the repository:

   git clone https://github.com/Meenachinmay/microservices-golang.git
   cd microservices-golang

2. Create an .env file in the root directory and set the necessary environment variables. An example .env file is provided as .env.example.

   cp .env.example .env

Running the Services

1. Build and run the services using Docker Compose using Makefile:

   make up_build

2. The services will be available at the following ports:

   • API Gateway: http://localhost:8080
   • Authentication Service: http://localhost:8081
   • Logger Service: http://localhost:8082
   • Mailer Service: http://localhost:8083
   • Listener Service: http://localhost:8084
   • Payment Service: http://localhost:8085

Services

API Gateway (Broker-service)

The API Gateway is the main entry point for all incoming requests. It routes requests to the appropriate service based on the action specified.

Authentication Service

The Authentication Service handles user authentication. It provides endpoints for login, signup, and password reset. (as of now just login is there for simulation, I will add more like signup, session, cookies and everything)

Logger Service

The Logger Service logs application events. It listens for log events from RabbitMQ and stores them in a log file.

Mailer Service

The Mailer Service sends emails. It listens for mail events from RabbitMQ and sends emails using the configured SMTP server. (I am using mailhog as of now, later I will use sendgrid)

Listener Service

The Listener Service listens for events from RabbitMQ and processes them. It handles log and mail events, delegating tasks to the appropriate services.

Payment Service

The payment service uses stripe payment gateway API to enable credit card payment for now. Payment service need to communicate with async calls with api-gateway and api-gateway with client, so for the communication between api-gateway and Payment service I am enabling gRPC calls, rather than using RabbitMQ. In this service I planned to use rabbitMQ to generate email invoices for payments on a completion of successful payments from users.

Technologies Used

• Golang: The primary language used for building the services.
• Docker: Used for containerizing the services.
• Docker Compose: Used for orchestrating the multi-container Docker application.
• RabbitMQ: Used for messaging between services.
• PostgreSQL: The database used by the Authentication Service.
• MongoDB: The database used by the Logger Service.
• gRPC: Communication method between api-gateway and other services where it needs async calls.

Command to generate gRPC code

     protoc --go_out=. --go_opt=paths=source_relative --go-grpc_out=. --go-grpc_opt=paths=source_relative <name of file>.proto

Service methods and Diagram

Services:

1. Api-gateway
2. Enquiry-service -> Postgres DB
3. Mail-service
4. Logger-service -> Postgres DB
5. Listener-service
6. frontend

DB tables:

• users table
• enquiry tables
• schedules table
• logs tables

Microservice communication

• http
• gRPC
• Rabbitmq message broker

Containerization

• Docker

Databases

• Postgres -> data store
• Redis -> Cache, Rate Limiting

3rd party API Integration

• Sendgrid

Service wise methods

Api-gateway

HTTP

func HandleSubmission(c *gin.Context)
func (lac *LocalApiConfig) FetchAllProperties(c *gin.Context)
func connect() (*amqp.Connection, error)

gRPC

func EnquiryViaGRPC(c *gin.Context, enquiryPayload types.EnquiryPayload)
func (lac *LocalApiConfig) GetAllLogs(c *gin.Context)
func (lac *LocalApiConfig) WriteLog(c *gin.Context)
func (lac *LocalApiConfig) CreateNewUser(c *gin.Context, userPayload types.UserPayload)

Enquiry-service

HTTP

func (localApiConfig *LocalApiConfig) HandleFetchAllProperties(c *gin.Context)

func StartGrpcServer(localApiConfig *handlers.LocalApiConfig)
func connect() (*amqp.Connection, error)
func connectToDB() *sql.DB
func ProcessScheduledTasks(s *handlers.EnquiryServer)

handlers

func StartGrpcUserServer(localApiConfig *handlers.LocalApiConfig)
func (e *EnquiryServer) HandleCustomerEnquiry(ctx context.Context, request *enquiries.CustomerEnquiryRequest) (*enquiries.CustomerEnquiryResponse, error)
func (e *EnquiryServer) getTotalEnquiriesLastWeek(c context.Context, updatedUser database.User) (int, error)
func (e *EnquiryServer) SendEmail(payload EnquiryMailPayloadUsingSendgrid) error
func (e *EnquiryServer) notifyUserAboutEnquiry(input *enquiries.CustomerEnquiry, totalEnquiries int, mailPayload EnquiryMailPayloadUsingSendgrid) error
func (e *EnquiryServer) executeTask(input *enquiries.CustomerEnquiry, mailPayload EnquiryMailPayloadUsingSendgrid) error
func (e *EnquiryServer) scheduleTask(input *enquiries.CustomerEnquiry, mailPayload EnquiryMailPayloadUsingSendgrid) error
func (u *UserServer) CreateNewUser(ctx context.Context, request *users.CreateUserRequest) (*users.CreateUserResponse, error)

rabbitmq actions

func (e *Emitter) declareExchange(ch *amqp.Channel) error
func (e *Emitter) Emit(event string) error
func NewEmitter(conn *amqp.Connection, exchange, routingKey string) (*Emitter, error)

Listener-service

rabbitmq actions

func DeclareExchange(ch *amqp.Channel) error
func DeclareRandomQueue(ch *amqp.Channel) (amqp.Queue, error)
func DeclareMailExchange(ch *amqp.Channel) error
func DeclareMailQueue(ch *amqp.Channel) (amqp.Queue, error)
func DeclareEnquiryMailQueue(ch *amqp.Channel) (amqp.Queue, error)
func NewLogConsumer(conn *amqp.Connection) (*LogConsumer, error)
func (consumer *LogConsumer) ConsumeLogs(topics []string) error
func logEvent(log LogPayload) error
func NewMailConsumer(conn *amqp.Connection) (*MailConsumer, error)
func (consumer *MailConsumer) ConsumeMails() error
func (consumer *MailConsumer) ConsumeEnquiryMails() error
func sendEnquiryMail(payload EnquiryMailPayloadUsingSendgrid) (time.Duration, error)
func logMailSendingResult(payload EnquiryMailPayloadUsingSendgrid, elapsed time.Duration, err error) error
func startLogConsumer(conn *amqp.Connection)
func startMailConsumer(conn *amqp.Connection)
func startEnquiryMailConsumer(conn *amqp.Connection)

Logger-service

HTTP

func (apiConfig *LocalApiConfig) WriteLog(c *gin.Context)

gRPC

func (l *LogServer) WriteLog(ctx context.Context, req *logs.LogRequest) (*logs.LogResponse, error)
func (l *LogServer) GetAllLogs(ctx context.Context, request *logs.GetAllLogsRequest) (*logs.GetAllLogsResponse, error)
func GRPCListener(localApiConfig *LocalApiConfig)

Mail-service

HTTP

func (app *Config) SendMailViaSendGrid(w http.ResponseWriter, r *http.Request)

Diagram

Contributing

Contributions are welcome! Please read the CONTRIBUTING.md file for more information on how to contribute to this project.

License

This project is licensed under the MIT License. See the LICENSE file for details.