Mastering WebSocket Load Balancing: Unlocking Resilience with Sticky IPs and Session Routing

Introduction

In high-demand real-time applications like ride-hailing or booking platforms, maintaining a stable connection between the client and server is crucial.

Load balancing for WebSocket connections presents unique challenges, especially in routing the client to the same backend instance consistently.

Here, we’ll explore two effective solutions: IP-based sticky sessions and WebSocket routing via session identifiers, detailing their benefits, limitations, and practical applications.

Example Scenario:

Imagine a booking app like Uber, where users rely on real-time updates for driver locations and estimated arrival times. Using IP-based sticky sessions ensures that once a user connects to a server instance, subsequent updates and data are delivered consistently from the same instance, preventing session disruptions.

Limitations:

• Can be unreliable for clients with dynamic IP addresses or those behind proxies/VPNs.


• IP address changes can disrupt session consistency, causing users to be routed to a different server.

Example Scenario:

In a ride-hailing app, once a user initiates a connection to track their driver, a session ID is assigned. The load balancer uses this session ID to ensure all updates and real-time notifications come from the same server instance, avoiding reconnections or missed messages.

Limitations:

• Requires additional setup to manage session ID generation and validation.


• Slightly more complex to implement compared to IP-based routing.

Comparison of Both Methods