The CI/CD and DevOps Blog

Kubernetes Tutorial: Deploying a load-balanced Docker application

Kubernetes is a Production grade container orchestration platform with automated scaling and management of containerized applications. It is also open source, so you can install Kubernetes on any cloud like AWS, Digital Ocean, Google Cloud Platform, or even just on your own machines on premises. Kubernetes was started at Google and is also offered as a hosted Container Service called GKE. With Shippable, you can easily hook up your automated DevOps pipeline from source control to deploy to your Kubernetes pods and accelerate innovation.

In this blog, we demonstrate how to deploy a load balanced, multi-container application to multiple Kubernetes environments on GKE. The deployment occurs in multiple stages in a Shippable defined workflow.


Kubernetes Deployment spec

The pods and services (load balancer) for the application are created using a deployment spec. Instead of creating and maintaining a deployment spec per environment which is a common practice, we create a single deployment spec template. This template has placeholders for the image and service/pod labels. When we deploy the application to a specific environment, we use powerful yet simple Shippable platform functions and resources to  replace these placeholders at run time when the deployment actually happens.

The deployment spec template (located here in our public repository) defines the label selectors placeholders in the .spec.selector section and the labels for the pods in the .spec.template.metadata.labels section. Labels are defined for both the front end voting application (FE_LABEL) as well as the Redis service (BE_LABEL) which the front ends makes API calls on via another load balancer.   

Configuring Multi-Stage CI

In this blog, we demonstrate how to use the Shippable platform to perform Multi-Stage CI on your repositories. The key benefit of Multi-Stage CI is to split a time-consuming CI process into smaller stages to detect issues in code quality / tests as early as possible and shorten the feedback loop on every checkin. This often entails refactoring or designing your application into smaller components and testing each component in isolation first before running more expensive integration tests of your component with other components in the system.

What is multi-stage CI?

In our multi-stage CI scenario, we split the CI of a Node.js app into several stages.

  • Stage 1: Stage 1 runs on every PR and lints the source code in the repository to find style errors. To learn more about the benifits of linting your javascript code, look at this article. The idea behind Stage 1 is to perform a quick code quality check on every PR and shorten the feedback loop for any errors in coding style and bugs found during static analysis. This allows developers to quickly find and fix issues in their PRs.
  • Stage 2: Stage 2 runs on successful completion of Stage 1. In Stage 2, we run a small subset of tests to quickly validate the PR.
  • Stage 3: Stage 3 runs on the merged commit to the repository. Here we run a broader set of core unit tests that take longer to run than Stage 2.