Building Resilient Real-Time Streaming Workers with DynamoDB Leases

Managing fleets of stateful real-time streaming workers that maintain hundreds of persistent WebSocket connections presents significant challenges in distributed systems. When workers fail, redeploy, or scale, ensuring that each connection is owned by exactly one healthy worker, and that ownership is gracefully transferred upon failure, is critical to prevent data loss and reduce operational overhead. This pattern demonstrates how to achieve resilient connection management using a lease-based approach with DynamoDB.

The Challenge: Statefulness in WebSocket Clients

Unlike stateless HTTP requests, WebSocket connections are persistent and bidirectional, requiring workers to maintain an open TCP connection and handle continuous message flow. This statefulness introduces several operational challenges for a worker fleet acting as WebSocket *clients*:

• Worker Failures: Unexpected worker termination drops connections, leading to data loss unless quickly reassigned.
• Rolling Deployments: Terminating old tasks during deployments drops connections, creating unmanaged connection windows.
• Horizontal Scaling: While adding workers is simple, gracefully removing them requires draining connections and verifying new ownership.
• Double-Claiming: Two workers attempting to own the same connection can lead to data duplication or errors.

Solution Overview: Distributed Lease Management with DynamoDB

The core of the solution is a distributed lease management system built on Amazon DynamoDB. Each WebSocket connection is represented by a lease record in DynamoDB, tracking its desired state, upstream URL, and crucially, its current owner (worker ID) and lease expiration time. DynamoDB's conditional writes are leveraged to provide atomic operations for acquiring and renewing leases, acting as a distributed lock.