2-dynamic

Dynamic API Load Balancer - Example

Membrane API Gateway can balance requests across backend nodes that are added and removed dynamically at runtime.

Nodes can be organized in clusters. You can manage them either through the web-based administration console or via a simple URL-based API.

What You Will Run

• One Membrane router as the load balancer
• Three sample web apps simulating backend nodes (ports 4000, 4001, 4002)
• A web-based admin console for cluster and node management
• An HTTP API for programmatic node control

Run the Example

1. Go to the examples/loadbalancing/2-dynamic directory.

   cd examples/loadbalancing/2-dynamic

2. Start Membrane:

   • macOS/Linux: ./membrane.sh
   • Windows: membrane.cmd

3. Open in a browser:

   http://localhost:4000
   

   You will see a simple counter app. Identical apps are also available on ports 4001 and 4002.

4. Open the Admin Console:

   http://localhost:9000/admin
   

5. Go to the Load Balancing tab.

   • Click the entry Default.
   • Enter Default as the cluster name.
   • Click Add Cluster.

6. Add the first node:

   • Host: localhost
   • Port: 4000
   • Click Add Node.

7. Open in a browser:

   http://localhost:8080
   

   Refresh a few times. All requests go to node 4000.

8. Add a second node (localhost:4001) using the same steps.

9. Open:

   http://localhost:8080
   

   Now requests are distributed between node 4000 and node 4001.

10. Add a third node (localhost:4002) to see full load balancing across three backends.

Managing Nodes with an API

Nodes can also be controlled programmatically using the Cluster Manager API. For example, to temporarily disable node localhost:4001:

curl "http://localhost:9010/clustermanager/down?balancer=default&host=localhost&port=4001"

Re-enable the node with .../up?balancer=....

Notes

• The adminConsole and clusterNotification interceptors in proxies.xml are optional. You can remove them if you only want programmatic control.
• This example defaults to round-robin balancing.

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See:

• proxies.xml
• balancer reference