Deploying loklak Server on Kubernetes with External Elasticsearch
Kubernetes is an open-source system for automating deployment, scaling, and management of containerized applications. - kubernetes.io Kubernetes is an awesome cloud platform, which ensures that cloud applications run reliably. It runs automated tests, flawless updates, smart roll out and rollbacks, simple scaling and a lot more. So as a part of GSoC, I worked on taking the loklak server to Kubernetes on Google Cloud Platform. In this blog post, I will be discussing the approach followed to deploy development branch of loklak on Kubernetes. New Docker Image Since Kubernetes deployments work on Docker images, we needed one for the loklak project. The existing image would not be up to the mark for Kubernetes as it contained the declaration of volumes and exposing of ports. So I wrote a new Docker image which could be used in Kubernetes. The image would simply clone loklak server, build the project and trigger the server as CMD - FROM alpine:latest ENV LANG=en_US.UTF-8 ENV JAVA_TOOL_OPTIONS=-Dfile.encoding=UTF8 WORKDIR /loklak_server RUN apk update && apk add openjdk8 git bash && \ git clone https://github.com/loklak/loklak_server.git /loklak_server && \ git checkout development && \ ./gradlew build -x test -x checkstyleTest -x checkstyleMain -x jacocoTestReport && \ # Some Configurations and Cleanups CMD ["bin/start.sh", "-Idn"] [SOURCE] This image wouldn’t have any volumes or exposed ports and we are now free to configure them in the configuration files (discussed in a later section). Building and Pushing Docker Image using Travis To automatically build and push on a commit to the master branch, Travis build is used. In the after_success section, a call to push Docker image is made. Travis environment variables hold the username and password for Docker hub and are used for logging in - docker login -u $DOCKER_USERNAME -p $DOCKER_PASSWORD [SOURCE] We needed checks there to ensure that we are on the right branch for the push and we are not handling a pull request - # Build and push Kubernetes Docker image KUBERNETES_BRANCH=loklak/loklak_server:latest-kubernetes-$TRAVIS_BRANCH KUBERNETES_COMMIT=loklak/loklak_server:kubernetes-$TRAVIS_COMMIT if [ "$TRAVIS_BRANCH" == "development" ]; then docker build -t loklak_server_kubernetes kubernetes/images/development docker tag loklak_server_kubernetes $KUBERNETES_BRANCH docker push $KUBERNETES_BRANCH docker tag $KUBERNETES_BRANCH $KUBERNETES_COMMIT docker push $KUBERNETES_COMMIT elif [ "$TRAVIS_BRANCH" == "master" ]; then # Build and push master else echo "Skipping Kubernetes image push for branch $TRAVIS_BRANCH" fi [SOURCE] Kubernetes Configurations for loklak Kubernetes cluster can completely be configured using configurations written in YAML format. The deployment of loklak uses the previously built image. Initially, the image tagged as latest-kubernetes-development is used - apiVersion: apps/v1beta1 kind: Deployment metadata: name: server namespace: web spec: replicas: 1 template: metadata: labels: app: server spec: containers: - name: server image: loklak/loklak_server:latest-kubernetes-development ... [SOURCE] Readiness and Liveness Probes Probes act as the top level tester for the health of a deployment in Kubernetes. The probes are performed periodically to ensure that things are working fine and appropriate steps are taken if they fail. When a new image is updated, the older pod still runs and servers the requests. It is replaced by the new ones only when the probes are…