su-tiko / k8s-deployment-strategies

Kubernetes deployment strategies explained

Kubernetes deployment strategies

In Kubernetes there is few different way to release an application, you have to carefully choose the right strategy to make your infrastructure resilient.

• recreate: terminate the old version and release the new one
• ramped: release a new version on a rolling update fashion, one after the other
• blue/green: release a new version alongside the old version then switch traffic
• canary: release a new version to a subset of users, then proceed to a full rollout
• a/b testing: release a new version to a subset of users in a precise way (HTTP headers, cookie, weight, etc.). This doesn’t come out of the box with Kubernetes, it imply extra work to setup a smarter loadbalancing system (Istio, Linkerd, Traeffik, custom nginx/haproxy, etc).
• shadow: release a new version alongside the old version. Incoming traffic is mirrored to the new version and doesn't impact the response.

Before experimenting, checkout the following resources:

• CNCF prensentation
• CNCF prensentation slides
• Kubernetes deployment strategies
• Six Strategies for Application Deployment.
• Canary deployment using Istio and Helm
• Automated rollback of Helm releases based on logs or metrics

Getting started

These examples were created and tested on Minikube running with Kubernetes v1.10.0.

$ minikube start --kubernetes-version v1.10.0 --memory 8192 --cpus 2

Visualizing using Prometheus and Grafana

The following steps describe how to setup Prometheus and Grafana to visualize the progress and performance of a deployment.

Install Helm

To install Helm, follow the instructions provided on their website.

$ helm init

Install Prometheus

$ helm install \
    --namespace=monitoring \
    --name=prometheus \
    --version=7.0.0 \
    stable/prometheus

Install Grafana

$ helm install \
    --namespace=monitoring \
    --name=grafana \
    --version=1.12.0 \
    --set=adminUser=admin \
    --set=adminPassword=admin \
    --set=service.type=NodePort \
    stable/grafana

Setup Grafana

Now that Prometheus and Grafana are up and running, you can access Grafana:

$ minikube service grafana

To login, username: admin, password: admin.

Then you need to connect Grafana to Prometheus, to do so, add a DataSource:

Name: prometheus
Type: Prometheus
Url: http://prometheus-server
Access: Server

Create a dashboard with a Graph. Use the following query:

sum(rate(http_requests_total{app="my-app"}[5m])) by (version)

To have a better overview of the version, add {{version}} in the legend field.

Example graph

Recreate:

Ramped:

Blue/Green:

Canary:

A/B testing:

Shadow: