Demo Telepresence Intercept

In this lesson, you’ll learn how to use Telepresence to intercept traffic from a Kubernetes service and run the workload locally for fast, iterative debugging.

Prerequisites

• A Kubernetes cluster and kubectl configured to the correct context
• Telepresence CLI installed (brew install telepresence or see the official docs)
• Node.js (v14+) and npm

1. List Your Deployments

Identify the deployment you want to intercept:

kubectl get deployment
# Example output:
# NAME             READY   UP-TO-DATE   AVAILABLE   AGE
# auth-depl        1/1     1            1           4h55m
# inventory-depl   1/1     1            1           5h32m
# products-depl    1/1     1            1           4h47m

2. Create an Intercept

First, connect Telepresence to your cluster if you haven’t already:

telepresence connect

Then run:

telepresence intercept auth-depl -p 8000:3000

Here’s the relevant snippet from the Kubernetes manifest:

# Deployment spec excerpt
spec:
  template:
    spec:
      containers:
      - name: auth
        image: sanjeevkt720/telepresence-auth
        ports:
        - containerPort: 3000
          name: web
---
apiVersion: v1
kind: Service
metadata:
  name: auth-service
spec:
  selector:
    app: auth
  ports:
    - port: 3000
      targetPort: 3000

You should see output similar to:

Using Deployment auth-depl
  Intercept name          : auth-depl
  State                   : ACTIVE
  Workload kind           : Deployment
  Destination             : 127.0.0.1:8000
  Service Port Identifier : 3000/TCP
  Volume Mount Point      : /tmp/telfs-1680244885
  Intercepting            : all TCP connections

3. Run the Service Locally

Switch to your local service directory and start the server on port 8000:

cd ~/telepresence/auth
npm install
npm run dev

Ensure your Express app listens on port 8000:

// index.js
const express = require("express");
const app = express();
const port = 8000;

app.get("/", (req, res) => {
  res.json({ message: "auth service running locally via Telepresence" });
});

app.listen(port, () => {
  console.log(`Auth service listening on port ${port}`);
});

4. Verify the Intercept

Use curl to hit the Kubernetes service name. Telepresence will route this to your local process:

curl http://auth-service:3000

Expected response:

{"message":"auth service running locally via Telepresence"}

5. Inspect the Pod

Observe both the original container and Telepresence’s traffic agent:

POD_NAME=$(kubectl get pod -l app=auth -o jsonpath='{.items[0].metadata.name}')
kubectl describe pod $POD_NAME

Look for two containers:

• auth (port 3000/TCP)
• traffic-agent (port 9900/TCP)

6. Remove the Intercept

When you’re done debugging, clear the intercept:

telepresence leave auth-depl
telepresence list
# Should report: No active intercepts

7. Switch to the Products Service

1. Stop your local auth service (Ctrl+C)

2. List deployments again:

   kubectl get deployment
   

3. Intercept the products deployment:

   telepresence intercept products-depl -p 8000:3000
   

4. Run the products service locally:

   cd ~/telepresence/products
   npm install
   npm run dev
   

5. Verify with:

   curl "http://products-service:3000/?product_ids=1,2,3"
   

8. Debugging an Error

If your request hangs and you see:

TypeError: Failed to parse URL from undefined?product_ids=1,2,3

Inspect your route handler:

app.get("/", async (req, res) => {
  try {
    const productIds = req.query.product_ids;
    const idsArray = productIds.split(",").map(id => parseInt(id, 10));
    const response = await fetch(`${apiURL}?product_ids=${idsArray.join(",")}`);
    // ...
  } catch (error) {
    console.error(error);
  }
});

9. Import Environment Variables

To mirror the Pod’s settings, pull the env vars into your local shell:

# Fetch one of the app pods
POD_NAME=$(kubectl get pod -l app=products -o jsonpath='{.items[0].metadata.name}')
# Export all environment variables from the container to your local session
kubectl exec $POD_NAME -- printenv | grep API_URL | sed 's/^/export /' > pod-env.sh
source pod-env.sh

Now restart your local service so it picks up API_URL and any other Pod-specific variables.

Links and References

• Telepresence Documentation
• Kubernetes Services
• Express.js Guide
• Docker Hub: sanjeevkt720/telepresence-auth