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Stateful Scaling: Laravel Session Management in Kubernetes Clusters

16-01-2024 12:45 PM

Kubernetes is an excellent option for scaling Laravel applications. Kubernetes offers scalability, high availability, service discovery, and load balancing. Specifically for Laravel deployments, Kubernetes can help with stateless horizontal scaling, easy management of background processing, and storage flexibility.
But it can come at a cost. The ephemerality of Kubernetes pods and the way they scale makes session management in Laravel difficult. Using the default file session driver can lead to lost data if the pod restarts or is replaced, so developers must shift to a different mechanism.
Here, we want to take you through some of the gotchas in Laravel session management you’ll experience as you move to a Kubernetes deployment. The good news is that they are all fixable with an understanding of the internal workings of containerization.

The Benefits of Using Kubernetes With Laravel
Let’s start with why you might want to do this. You can deploy Laravel applications in myriad different ways, so why choose one that will immediately give you this session headache? Well, the core benefits of deploying a Laravel application on Kubernetes are:

1.Stateless horizontal scaling. Laravel is inherently designed to be stateless for most of its components (excluding sessions and cache if stored locally). This design complements Kubernetes’ scaling capabilities. When traffic to your Laravel application increases, Kubernetes can quickly spawn more replicas of your Laravel application to handle the load, and vice-versa when traffic decreases.

2.Background processing. Laravel’s job and queue system, built around tools like Laravel Horizon, can benefit from Kubernetes’ deployment strategies. For instance, worker containers can be scaled independently of the main application, allowing for effective processing of queued jobs.

3.Configuration management. Laravel’s configuration system relies heavily on environment variables. Kubernetes’ ConfigMaps and Secrets make it easy to manage and inject these environment variables consistently and securely across different environments (development, staging, production).

4.Storage flexibility. If your Laravel application requires file storage (for example, for user uploads), Kubernetes offers Persistent Volume Claims (PVCs) that abstract the underlying storage backend. This means your Laravel application can seamlessly store files whether you’re on cloud object storage, a block storage device, or a network file system.

5.Service mesh integration. If you adopt a service mesh like Istio with your Laravel application on Kubernetes, you gain enhanced observability, traffic management, and security features without modifying the Laravel application itself.

However, while Kubernetes offers these benefits, it also introduces complexity, with session management being a casualty of this complexity. One of the benefits above is a primary culprit in causing session management problems–stateless horizontal scaling. This causes session management problems by introducing multiple replicas of your Laravel application, which may not inherently share session state.
In traditional single-server setups, a user’s session data is typically stored locally, making it instantly available for subsequent requests from that user. In Kubernetes, with multiple replicas handling requests, a user may be served by a different replica with each request.