Email Queue Implementation

Overview

This is a scalable email queue implementation in Go, utilizing Redis for queue management and providing a flexible email sending system with retry mechanisms and template support.

Features

• Redis-backed Queue: Leverages Redis for reliable email task queuing
• Retry Mechanism: Automatic retries for failed email sends
• Template Engine: Supports dynamic email templating
• Configurable: Highly configurable through environment variables
• SMTP Email Sending: Supports configurable SMTP email sending
• Bulk Email Sending: Support for sending multiple emails in a single request

API Endpoints

Health Check

• Endpoint: GET /health
• Description: Checks the health of the application
• Response:

  {
    "status": "ok",
    "timestamp": {
      "server": {
        "time": "2024-03-27T10:15:30Z",
        "timezone": "UTC"
      }
    }
  }

Single Email Send

• Endpoint: POST /api/send
• Description: Enqueue a single email to be sent
• Request Body:

  {
    "to": "[email protected]",
    "subject": "Mail regarding license update",
    "templateName": "license_update",
    "data": {
      "username": "License creator"
    }
  }

• Successful Response:

  {
    "message": "email was successfully added to the queue",
    "details": {
      "recipient": "[email protected]",
      "subject": "Mail regarding license update"
    }
  }

• Error Responses:
  • 400 Bad Request: Validation errors
  • 500 Internal Server Error: Queueing failure

Bulk Email Send

• Endpoint: POST /api/bulk-send

• Description: Enqueue multiple emails in a single request

• Request Body:

  {
    "emails": [
      {
        "to": "[email protected]",
        "subject": "Welcome User 1",
        "templateName": "license_update",
        "data": {
          "username": "License creator"
        }
      },
      {
        "to": "[email protected]",
        "subject": "Welcome User 2",
        "templateName": "license_update",
        "data": {
          "username": "License creater"
        }
      }
    ]
  }

• Request Validation:

  • Minimum 1 email
  • Maximum 50 emails per request

• Successful Response (All emails queued):

  {
    "message": "all emails successfully queued",
    "successCount": 2,
    "successEmails": [
      "[email protected]",
      "[email protected]"
    ]
  }

• Partial Success Response:

  {
    "message": "partial success in queueing emails",
    "successCount": 1,
    "failedCount": 1,
    "successEmails": ["[email protected]"],
    "failedEmails": ["[email protected]"]
  }

Configuration

Environment Variables

Variable	Description	Default
SERVER_PORT	HTTP server port	8080
CACHE_HOST	Redis host	localhost
CACHE_PORT	Redis port	6379
CACHE_PASSWORD	Redis password	""
CACHE_DB_INDEX	Redis database index	0
EMAIL_SMTP_SERVER	SMTP server address	smtp.gmail.com
EMAIL_SMTP_PORT	SMTP server port	587
EMAIL_SMTP_USERNAME	SMTP username	[email protected]
EMAIL_SMTP_PASSWORD	SMTP password	-
EMAIL_SENDER_ADDRESS	Sender email address	[email protected]
EMAIL_SENDER_NAME	Sender display name	Rohan

Email Queue Workflow

1. Create an EmailTask with recipient, subject, template, and data
2. Enqueue the email task to Redis
3. Background worker picks up the task
4. Attempts to send email with configurable retries
5. Logs success or failure

Retry Strategy

• Maximum retries: 3
• Retry delay: 5 seconds between attempts
• Queue check interval: 1 second

Installation

# Clone the repository
git clone https://github.com/rohansen856/redis-go-mailing-bulk.git

# Set required environment variables

# Run the application
go run ./cmd/server/main.go

Dependencies

• Go 1.20+
• Redis
• gin-gonic/gin
• go-redis/redis
• html/template standard library

Performance Considerations

• Uses connection pooling for Redis
• Non-blocking queue processing
• Configurable pool sizes and timeouts
• Structured logging for performance tracking

Security

• URL and HTML escaping in templates
• Configurable SMTP authentication
• Environment-based configuration management
• Input validation for email tasks

Authors

Rohan