Fast development workflow with Docker and Kubernetes

Keeping development environments in sync is a constant pain. Containerizing your development environment enables your service to run in the exact same environment everywhere, from your laptop to production (for more details on the benefits of a container native development workflow, see this post by Matt Butcher.)

Telepresence, in conjunction with a containerized development environment, gives the developer a fast development workflow in developing a multi-container application on Kubernetes. Telepresence lets you run a Docker container locally while proxying it to your Kubernetes cluster.

In this HOWTO, we'll walk through how to use Telepresence with a containerized Docker environment to build a fast development workflow.

Quick example

We'll start with a quick example. Apply this manifest to create a deployment and service both named hello-world, exposed on port 8000. Then confirm that the deployment becomes ready:

It may take a minute or two for the pod running the server to be up and running, depending on how fast your cluster is.

You can now run a Docker container using Telepresence that can access that service, even though the process is local but the service is running in the Kubernetes cluster:

Setting up a development environment in Docker

So how would we use Telepresence to do actual development of the hello-world service? We'll set up a local Dockerized development environment for hello-world. Clone the hello-world repo:

In the repository is a Dockerfile that builds a runtime environment for the hello-world service.

Build the runtime environment and tag it hello-dev:

We'll use Telepresence to swap the hello-world deployment with the local Docker image. Behind the scenes, Telepresence invokes docker run, so it supports any arguments you can pass to docker run. In this case, we're going to also mount our local directory to /usr/src/app in your Docker container. Make sure your current working directory is the hello-world directory, since we're going to mount that directly into the container.

We can test this out. In another terminal, we'll start a pod remotely on the Kubernetes cluster.

Let's change the message in server.py. At a shell prompt in the hello-world directory, modify the file using sed:

or just use your editor to change the file. The change we have made is very simple:

Rerun the curl command from your remote pod:

Notice how the output has updated in realtime. Congratulations! You've now:

• Routed the hello-world service to the Docker container running locally
• Configured your Docker service to pick up changes from your local filesystem
• Made a live code edit and seen it immediately reflected in production

How it works

Telepresence will start a new proxy container and then call docker run with whatever arguments you pass to --docker-run to start a container that will have its networking proxied. All networking is proxied:

• Outgoing to Kubernetes.
• Outgoing to cloud resources outside the cluster
• Incoming connections from the cluster to ports specified with --expose.

Volumes and environment variables from the remote Deployment are also available in the container.

Cleaning up and next step

• Quit your remote pod shell (exit) to clean up that pod.
• Press Ctrl-C at your Telepresence terminal. Telepresence will swap the deployment back to its original state.
• In a real development situation, you would commit your development work and let CI do its thing. Or build and deploy your changes however you normally would.

Still have questions? Ask in our Slack chatroom or file an issue on GitHub