Demo Env file

In this guide, we’ll walk through intercepting the products deployment with Telepresence, exporting its Kubernetes environment variables into a .env file, and running the service locally so it can call the inventory service exactly as it does inside the cluster.

1. Reproducing the Error

First, start an intercept on the products deployment:

telepresence intercept products-depl -p 8000

When you request multiple products, you’ll see this in your local logs:

TypeError: Failed to parse URL from undefined?product_ids=1,2,3
    at new URL (node:internal/url:816:29)
    at new Request (node:internal/deps/undici:9474:25)
    at fetch (node:internal/deps/undici:10203:26)
  code: 'ERR_INVALID_URL',
  input: 'undefined?product_ids=1,2,3'
}

This error shows that API_URL is undefined in your local environment.

2. Application Code (index.js)

The service reads API_URL from the environment and queries the inventory service:

const express = require("express");
const fetch = require("node-fetch");
const app = express();
const port = 8000;

const apiURL = process.env.API_URL; // undefined when running without .env
console.log("API_URL:", apiURL);

const products = [
  { id: 1, name: "iphone 14", price: 900, category: "electronics", onSale: false },
  { id: 2, name: "Samsung 40in TV", price: 500, category: "electronics", onSale: true },
  { id: 3, name: "Apple MacbookPro", price: 2500, category: "electronics", onSale: false }
];

app.get("/", async (req, res) => {
  try {
    const productIds = req.query.product_ids;
    const idsArray = productIds.split(",").map(id => parseInt(id.trim(), 10));
    const filtered = products.filter(p => idsArray.includes(p.id));

    const response = await fetch(`${apiURL}?product_ids=${idsArray.join(",")}`);
    if (!response.ok) throw new Error(`HTTP error! Status: ${response.status}`);

    const data = await response.json();
    res.json({ data });
  } catch (error) {
    console.error(error);
    res.status(500).send("Internal Server Error");
  }
});

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

3. Kubernetes Deployment Spec

Normally, the Pod spec injects API_URL:

spec:
  template:
    spec:
      containers:
        - name: products
          ports:
            - containerPort: 8000
              name: web
          env:
            - name: API_URL
              value: "http://inventory-service:3000/"
---
apiVersion: v1
kind: Service
metadata:
  name: products-service
spec:
  type: LoadBalancer

Since Telepresence runs the container locally, those Pod environment variables won’t be available by default.

4. Pulling Environment Variables with Telepresence

1. Stop and remove the current intercept

   telepresence list
   telepresence leave products-depl
   

2. Restart with .env dump and mount

   telepresence intercept products-depl \
     -p 8000 \
     --env-file my-envs.env \
     --mount=true
   

   This generates my-envs.env:

   API_URL=http://inventory-service:3000/
   AUTH_SERVICE_PORT=tcp://10.100.10.52:3000
   INVENTORY_SERVICE_PORT_3000_TCP_ADDR=10.100.246.69
   KUBERNETES_PORT_443_TCP_ADDR=10.100.1.1
   ...
   

5. Loading the .env File in Node.js

Install and configure dotenv:

npm install dotenv

At the top of index.js, override existing env vars:

require("dotenv").config({ override: true });
const express = require("express");
const fetch = require("node-fetch");
// ... rest of the code ...

Now when you run the intercept, process.env.API_URL matches the cluster’s value.

6. Testing the Setup

With the intercept active, send a request through your cluster’s LoadBalancer:

curl http://a45190821a848c3d9760c9e3b9-515600148.us-east-1.elb.amazonaws.com:3000/?product_ids=1,2,3

You should receive:

{
  "data": [
    {
      "id": 1,
      "name": "iphone 14",
      "price": 900,
      "category": "electronics",
      "onSale": false,
      "inventoryCount": 158
    },
    {
      "id": 2,
      "name": "Samsung 40in TV",
      "price": 500,
      "category": "electronics",
      "onSale": true,
      "inventoryCount": 54
    },
    {
      "id": 3,
      "name": "Apple MacbookPro",
      "price": 2500,
      "category": "electronics",
      "onSale": false,
      "inventoryCount": 607
    }
  ]
}

This confirms that your local service reads the same environment variables as in Kubernetes and correctly calls the inventory service.

Links and References

• Telepresence Documentation
• dotenv on npm
• node-fetch GitHub