Image Metadata Service

A REST API service for storing, retrieving, and searching image metadata using Redis as the backend storage and caching layer.

Features

• Fast Storage & Retrieval: Store and retrieve image metadata with Redis hash structures
• Advanced Search: Search images by tags, format, and size with intelligent caching
• Performance Optimized: Built-in search result caching with automatic cache invalidation
• Statistics Dashboard: Real-time service statistics including memory usage
• RESTful API: Clean HTTP endpoints for all operations

Prerequisites

• Go 1.25.1 or higher
• Redis server running on localhost:6379

Installation

1. Clone the repository:

git clone https://github.com/ajitashwath/image-metadata.git
cd image-metadata

2. Install dependencies:

go mod tidy

3. Start Redis server (in WSL):

redis-server

4. Run the service:

go run main.go

The service will start on http://localhost:8080

API Endpoints

Store Image Metadata

POST /images

Store metadata for a new image.

Request Body:

{
  "id": "img001",
  "name": "sunset.jpg",
  "tags": ["nature", "sunset", "landscape"],
  "size": 1024000,
  "format": "jpg",
  "width": 1920,
  "height": 1080
}

Response:

{
  "status": "stored"
}

Get Image by ID

GET /images/{id}

Retrieve metadata for a specific image.

Response:

{
  "id": "img001",
  "name": "sunset.jpg",
  "tags": ["nature", "sunset", "landscape"],
  "size": 1024000,
  "format": "jpg",
  "width": 1920,
  "height": 1080
}

Search Images

GET /search?q={query}

Search for images using various criteria.

Query Formats:

• tag:nature - Search by tag
• format:jpg - Search by format
• size:>500000 - Search by size (greater than)
• size:<2000000 - Search by size (less than)

Response:

{
  "query": "tag:nature",
  "count": 2,
  "results": [
    {
      "id": "img001",
      "name": "sunset.jpg",
      "tags": ["nature", "sunset"],
      "size": 1024000,
      "format": "jpg",
      "width": 1920,
      "height": 1080
    }
  ]
}

Service Statistics

GET /stats

Get service statistics and Redis memory usage.

Response:

{
  "total_images": 150,
  "cached_searches": 25,
  "redis_memory_usage": "2.5M"
}

Usage Examples

Store Image Metadata

curl -X POST http://localhost:8080/images \
  -H "Content-Type: application/json" \
  -d '{
    "id": "img001",
    "name": "mountain.jpg",
    "tags": ["nature", "mountain", "landscape"],
    "size": 2048000,
    "format": "jpg",
    "width": 2560,
    "height": 1440
  }'

Search by Tag

curl "http://localhost:8080/search?q=tag:nature"

Search by Format

curl "http://localhost:8080/search?q=format:png"

Search by Size

# Images larger than 1MB
curl "http://localhost:8080/search?q=size:>1000000"

# Images smaller than 500KB
curl "http://localhost:8080/search?q=size:<500000"

Get Specific Image

curl http://localhost:8080/images/img001

Get Service Statistics

curl http://localhost:8080/stats

Architecture

Data Storage

• Image Metadata: Stored as Redis hashes with key pattern image:{id}
• Tag Indexes: Redis sets with key pattern tag:{tagname} containing image IDs
• Format Indexes: Redis sets with key pattern format:{format} containing image IDs

Caching Strategy

• Search results are cached for 5 minutes using key pattern search:{query}
• Cache is automatically invalidated when new images with matching tags/formats are stored
• Cache hits and misses are logged for monitoring

Performance Features

• Indexed Searches: Fast O(1) lookups for tags and formats using Redis sets
• Intelligent Caching: Search results cached with automatic invalidation
• Bulk Operations: Efficient batch processing for search results
• Memory Monitoring: Real-time Redis memory usage tracking

Configuration

The service uses the following default Redis configuration:

• Host: localhost
• Port: 6379
• Database: 0

To modify these settings, update the NewService() function in main.go.

Error Handling

The API returns appropriate HTTP status codes:

• 200 OK - Successful operations
• 400 Bad Request - Invalid request format or query
• 404 Not Found - Image not found
• 500 Internal Server Error - Server-side errors

Dependencies

• gorilla/mux: HTTP router for REST endpoints
• go-redis/redis/v8: Redis client for data storage
• Standard Library: JSON encoding, HTTP handling, logging

Development

Running Tests

go test ./...

Building for Production

go build -o image-service main.go
./image-service

Monitoring

The service provides built-in monitoring through:

• Request logging for cache hits/misses
• Redis memory usage statistics
• Image count and cached search metrics

Access monitoring data via the /stats endpoint or check application logs.