Previous:Why your development workflow is so important for microservices
A basic development workflow for Kubernetes services lets a developer write some code, commit it, and get it running on Kubernetes. It's also important that your development environment be as similar as possible to production, since having two different environments will inevitably introduce bugs. In this tutorial, we'll walk through a basic development workflow that is built around Kubernetes, Docker, and Envoy/Ambassador.
This tutorial relies on two components in the cloud, Kubernetes and Ambassador. If you haven't already, go ahead and set them up.
You need a development environment for Kubernetes services. We recommend the following approach:
You'll need the following tools installed on your laptop:
kubectl, to manage your deployment
Go ahead and install them now, if you haven't already.
In a traditional application, the release / operations team manages the deployment of application updates to production. In a microservices architecture, the team is responsible for deploying service updates to production.
We're going to deploy and publish a microservice, from source, into Kubernetes.
We've created a simple Python microservice that you can use as a template for your service. This template includes:
Dockerfilethat specifies how your development environment and runtime environment are configured and built.
service.yamlfile that customizes deployments for different scenarios (e.g., production, canary, development).
k8s/deployment.yaml) that defines how the service is run in Kubernetes. It also contains the annotations necessary to configure Ambassador for the given service.
git clone https://github.com/datawire/hello-world-python
We're going to use Forge to automate and template-ize the deployment process. Run the Forge configuration process:
The process of getting a service running on a Kubernetes cluster involves a number of steps: building a Docker image, pushing the image to a repository, instantiating a Kubernetes manifest to point to the image, and applying the manifest to the cluster. We're going to tell Forge to use the
stable profile, which will deploy the service in a production configuration (by default, Forge is set up to deploy to development). Forge automates this entire process of deployment:
cd hello-world-python forge --profile stable deploy
Now, we're going to test the service. Get the external IP address of Ambassador:
kubectl get services ambassador NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE ambassador 10.11.250.208 126.96.36.199 80:31622/TCP 4d
Access the service via Ambassador:
curl 188.8.131.52/hello/ Hello World (Python)! (up 0:03:13)
When developing, you want a fast feedback cycle. You'd like to make a code change, and immediately be able to build and test your code. The deployment process we just went through adds latency into the process, since building and deploying a container with your latest changes takes time. Yet, running a service in Kubernetes lets that service access other cloud resources (e.g., other services, databases, etc.).
Telepresence lets you develop your service locally, while creating a bi-directional proxy to a remote Kubernetes cluster.
You'd like for your development environment to be identical to your runtime environment. We're going to do that by using the exact same Dockerfile we use for production to build a development image. Make sure you're in the
hello-world-python directory, and type:
docker build . -t hello-world-dev
Now, we can swap the existing
hello-world service on Kubernetes for a version of the same service, running in a local container.
telepresence --swap-deployment hello-world-stable --docker-run \ --rm -it -v $(pwd):/service hello-world-dev:latest
(Note that Forge has automatically appended a
stable suffix to the deployment name to indicate that the service has been deployed with the
stable profile specified in the
docker run to start the container. It also mounts the local filesystem containing the Python source tree into the container. Change the "Hello World" message in
app.py to a different value:
def root(): return "Hello World via Telepresence! (up %s)\n" % elapsed()
Now, if we test our service via Ambassador, we'll see that we're now routing to the modified version of our service.
curl 184.108.40.206/hello/ Hello World via Telepresence! (up 0:04:13)
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