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Kubernetes in Practice

Dealing with Bad Releases

Learn how we can manually and automatically prevent bad releases.

We'll cover the following...

Deployments also allow us to mitigate the risk of a bad release either by letting us manually rollback this release or by automatically preventing this release from happening.

Let’s test that out by creating a new version that simulates an issue. Here’s the updated code for our app:

Manually blocking the bad release

Ruby
require "sinatra"
set :bind, "0.0.0.0"
$counter = 0
get "*" do
  $counter += 1
  if $counter > 3
    raise "Whoops, something is wrong"
  end
  "[buggy] Hello, Kubernetes!\n"
end

After three successful responses, the app crashes with an exception. This allows us to simulate a case where the app starts running correctly but after some time it starts failing. We’ve pushed this buggy image to Docker Hub by using the following commands:

Rust 1.40.0
docker build . -t brianstorti/hellok8s:buggy
docker push brianstorti/hellok8s:buggy

Let’s update the manifest to start using this new image.

YAML
apiVersion: apps/v1
kind: Deployment
metadata:
  name: hellok8s
spec:
  replicas: 2
  selector:
    matchLabels:
      app: hellok8s
  template:
    metadata:
      labels:
        app: hellok8s
    spec:
      containers:
      - image: brianstorti/hellok8s:buggy
        name: hellok8s-container

We can apply this manifest using the following command to see the rolling update happening again until all the pods running are using this new ...