How to Create Routing for Apps Deployed via Spring Cloud Data Flow in Kubernetes

Learn how to enable external access to applications running in a Kubernetes cluster with Spring Cloud Data Flow, similar to PCF routing.
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How to Create Routing for Apps Deployed via Spring Cloud Data Flow in Kubernetes

Setting up external access to applications deployed in a Kubernetes cluster using Spring Cloud Data Flow can be challenging, especially for teams migrating from platforms like PCF (Pivotal Cloud Foundry) where routes are straightforward. In this guide, we will tackle the issue of enabling external access to your deployed apps in Kubernetes, focusing on creating routes that can efficiently replace your previous PCF routes.

Understanding the Problem

When deploying applications using Spring Cloud Data Flow in a Kubernetes environment, many users find that accessing their apps from outside the cluster isn't as intuitive as it was with PCF. While PCF offers a straightforward way to specify domains and routes, Kubernetes doesn't inherently include similar constructs. Instead, Kubernetes requires users to configure Services to manage access.

Common Challenges

No simple equivalent to PCF routes: Kubernetes requires more manual configuration of services.

Pending external IPs: Using LoadBalancer services can sometimes result in a pending state.

Configuration not reflecting in SCDF dashboard: Missing properties or configurations can lead to confusion.

Solution Breakdown

In this section, we'll explore how to create an equivalent route in Kubernetes for your Spring Cloud Data Flow applications, using the correct service types and deployment properties.

Step 1: Set Deployment Properties

When deploying your stream applications, you need to specify the following property to create a LoadBalancer type service:

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This configuration instructs Kubernetes to create a service that exposes the application externally via a cloud provider's load balancer.

Step 2: Deploy Your Stream Application

Assuming you are deploying a stream named httplogger that includes an HTTP sink, the deployment will automatically create a service of type LoadBalancer as long as your cluster supports it.

Step 3: Access the External URL

Once your stream is up and running, you can retrieve the external URL for your application using the following command with curl and jq:

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Explanation of the command:

The command fetches the JSON representation of the stream's status.

Using jq, it extracts the external URL of the http application in the stream.

Step 4: Troubleshooting Pending External IPs

If you encounter a pending external IP when deploying your load balancer:

Ensure that your Kubernetes cluster is set up with a cloud provider that supports external load balancers.

Check your cluster's resource limits and configurations to ensure that load balancer requests aren't being throttled.

Alternative: Using NodePort

While the LoadBalancer service type is ideal, you might also consider using the NodePort service type, which exposes the service on a port of each node in the cluster. For this, you’d specify the following property:

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This method can be useful for development purposes or internal access, but it's less suited for applications needing stable external access.

Conclusion

Enabling external routing for applications deployed via Spring Cloud Data Flow in Kubernetes requires understanding the different service types and configuring your deployment properties correctly. By setting the appropriate properties and making use of Kubernetes services, you can create a configuration that mirrors the simplicity of PCF routes.

If you follow the steps outlined in this post, you should be equipped to set external access for your applications and ease your migra

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