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05_google_kubernetes_engine.md

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Definition

Google Kubernetes Engine is an implementation of containers as a service (CaaS) technology. Basically it's a K8s managed platform.

Creation

This is a 3-node cluster deployed to the us-east-1b zone running on n1-standard-1 machine:

gcloud container clusters create simple-gke-cluster --zone us-east-1b --machine-type n1-standard-1

Much of a cluster's configuration is immutable(cannot be changed without deleting the cluster and recreating it with a different configuration)

The high-level constructs that make up a GKE cluster include:

  • Container clusters == deployable units that can be created, scheduled, and managed. They are a logical collection of containers that belong to an application.
  • Nodes == workers that run tasks as delegated by the master. Nodes can run one or more container clusters. Each provides an application-specific virtual host in a containerized environment.
  • Cluster master - the central control point that provides a unified view of the cluster. There is a single master node that controls multiple nodes.

GCP Container Registry (GCR) provides a secure, reliable, and performant location to store all docker images. Main advantages:

  • Automatically building and pushing container images to Container Registry from your source repository
  • Triggering builds by source code or tag changes in Google Cloud Source Repositories, GitHub, or Bitbucket
  • Running unit tests, export artifacts, and more as part of your CI/CD pipelines

Deployment

There are 3 options:

  • kubectl run using command line parameters
  • kubectl apply using YAML deployment file
  • Kubernetes Engine Workloads dashboard (can generate the YAML deployment file for a workload, and consequently switch to option #2)

Exposing GKE Services

  • Cluster IP: Exposes the workload via internal IP to the cluster
  • Node port: Exposes the workload via a specific port on each node within the cluster
  • Load balancer: Creates a load balancer which then exposes the workload via an external IP address

Creating/Storing secrets

kubectl create secret generic creds --from-literal=username=user1 --from-literal=password=pwd
kubectl create secret generic credentials --from-file ./username.txt --from-file ./password.txt

Rolling Updates

  1. Building a new image:
docker build -t gcr.io/${PROJECT_ID}/hello-world-upd:v2
  1. Uploading updated image (either manually or via an automated process) to Google Container Registry:
gcloud docker -- push gcr.io/${PROJECT_ID}/hello-world-upd:v2
  1. The actual rolling update command is quite straightforward, with all the heavy lifting being performed under the covers by GKE and Kubernetes:
kubectl set image deployment/hello-world hello-world=gcr.io/${PROJECT_ID}/hello-world-upd:v2

Rolling back

kubectl rollout undo deployment/$(DEPLOYMENT_NAME) --to-revision=2