Demo Volumes

Intercept a Kubernetes pod using Telepresence, mount its ConfigMap volume on your local machine, and access configuration data as if the service were running in-cluster.

Table of Contents

• Prerequisites
• Node.js Service Example
• Kubernetes Deployment with ConfigMap Volume
• ConfigMap Definition
• Intercepting with Telepresence and Mounting Volumes
• Exploring the Mounted Volume
• Customizing the Local Mount Path
• References

Prerequisites

• Kubernetes cluster access with kubectl configured
• Telepresence installed
• A local .env file for environment variables

Node.js Service Example

The products service is an Express.js app that reads API_URL from environment variables:

require('dotenv').config({ override: true });
const express = require("express");
const app = express();
const port = 8000;

const apiURL = process.env.API_URL;
console.log("API_URL:", apiURL);

const products = [
  {
    id: 1,
    name: "iPhone 14",
    price: 900,
    category: "electronics",
    onSale: false,
  },
];

app.get("/products", (req, res) => {
  res.json(products);
});

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

Kubernetes Deployment with ConfigMap Volume

Deploy the products-depl Deployment and mount a ConfigMap called db-info at /tmp:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: products-depl
spec:
  selector:
    matchLabels:
      app: products
  template:
    metadata:
      labels:
        app: products
    spec:
      volumes:
        - name: db-config
          configMap:
            name: db-info
      containers:
        - name: products
          image: sanjeevkt720/telepresence-products
          imagePullPolicy: Always
          ports:
            - containerPort: 8000
              name: web
          volumeMounts:
            - name: db-config
              mountPath: /tmp
          env:
            - name: API_URL
              value: "http://api.example.com"

ConfigMap Definition

Define your database connection details in a ConfigMap:

apiVersion: v1
kind: ConfigMap
metadata:
  name: db-info
data:
  DB_HOST: "prod.db"
  DB_USERNAME: "myusername123"
  DB_PASSWORD: "mypassword123"

Intercepting with Telepresence and Mounting Volumes

1. Check for existing intercepts:

   telepresence list
   

2. Create an intercept on port 8000, inject your .env, and mount the pod’s volumes:

   telepresence intercept products-depl \
     --port 8000 \
     --env-file .env \
     --mount
   

Example output (identifiers will vary):

Using Deployment products-depl
  Intercept name          : products-depl
  State                   : ACTIVE
  Workload kind           : Deployment
  Destination             : 127.0.0.1:8000
  Service Port Identifier : 8000/TCP
  Volume Mount Point      : /tmp/telfs-2391723209
  Intercepting            : all TCP connections

Exploring the Mounted Volume

In a new terminal:

cd /tmp/telfs-2391723209/tmp
ls
cat DB_HOST
# prod.db

You now have file-based access to the ConfigMap data.

Customizing the Local Mount Path

1. End the current intercept:

   telepresence leave products-depl
   

2. Start a new intercept with a custom mount location:

   telepresence intercept products-depl \
     --port 8000 \
     --env-file .env \
     --mount=/tmp/example123
   

Files now appear under /tmp/example123/tmp:

cd /tmp/example123/tmp
ls
# DB_HOST  DB_PASSWORD  DB_USERNAME

Adjust your application or use symbolic links to consume these local files seamlessly.

References

• Telepresence Documentation
• Kubernetes ConfigMap
• Kubernetes Deployments
• Express.js Guide