Resizer Service

The Resizer service is responsible for resizing images using imgproxy. It connects to the render-queue service via Redis Streams to get resize tasks.

Architecture

The service works with two key components:

1. Redis Streams for task distribution
2. imgproxy for actual image resizing

Task Processing Flow

1. Resize tasks are published to a Redis Stream (resize_stream) by other services
2. Multiple resizer instances join a consumer group (resize_group) to read tasks in a round-robin fashion
3. Each instance processes its tasks and acknowledges completion
4. If a task processing fails, it remains in the "pending" state and can be claimed by other instances

Features

• Horizontal Scaling: Multiple resizer instances can work together through Redis Streams consumer groups
• Fault Tolerance: If one instance fails, tasks are automatically redistributed
• Load Balancing: Tasks are distributed evenly across all resizer instances
• Retry Mechanism: Automatically claims failed tasks after a timeout period

Configuration

The service can be configured using environment variables:

| Variable | Description | Default | | ---------------------- | ----------------------------------------------- | ----------------------- | | IMGPROXY_URL | URL of the imgproxy service | http://localhost:8101 | | MAX_CONCURRENT_TASKS | Maximum number of tasks to process concurrently | 3 | | HEALTH_PORT | Port for the health check server | 8095 | | REDIS_ADDR | Redis server address (host:port) | localhost:6379 | | REDIS_PASSWORD | Redis password | "" (empty) | | CONSUMER_ID | Optional unique ID for this consumer | Auto-generated |

Installation and Setup

Local Development

1. Install dependencies:

   npm install

2. Make sure Redis is running and accessible at your configured REDIS_ADDR

3. Start the service in development mode:

   npm run dev

Docker Deployment

1. Build the Docker image:

   npm run docker:build

2. Run the container:

   docker run -p 8095:8095 --env-file .env -d snowcone-monorepo-resizer

Health Check

The service provides a health check endpoint at:

GET http://localhost:8095/healthz

Task Queuing

Tasks are added to the Redis Stream by the render-queue service. The task format is:

{
  "id": "resize_12345678",
  "type": "resize",
  "params": {
    "params": {
      "assetUrl": "https://example.com/image.jpg",
      "maxWidth": 800,
      "tempFileUrlForResizer": "https://example.com/temp-file.jpg"
    },
    "callbackUrl": "https://callback.example.com/endpoint"
  }
}

Monitoring

You can monitor the Redis Streams and consumer groups using Redis CLI:

# View tasks in the resize stream
redis-cli XRANGE resize_stream - + COUNT 10

# View consumer group info
redis-cli XINFO GROUPS resize_stream

# View pending tasks (not acknowledged)
redis-cli XPENDING resize_stream resize_group