dyvakumar/myproject

#Create a CI/CD Pipeline For a Java Application

In this lab, we are building a continuous delivery (CD) pipeline. We are using a very simple application written in Java (Hello World). For the sake of simplicity, we are going to run only one type of test against the code. The prerequisites for this lab are as follows:

Run & test the application from CLI

Jenkins instance

Create a Docker image, run the container and test it

Create Kubernetes deployment and test it

Let’s get started!

Step 01 :

A running Jenkins instance. It must be publicly accessible from the internet so that the repository can connect to Jenkins through web-hooks.

Image registry: Docker Registry is used to create Images.

An account on GitHub.

The pipeline can be created as follows:

Create a CI/CD pipeline with Kubernetes and Jenkins.

The Application Files Our sample application will respond with ‘Hello World’ to any GET request. Create a new file called App.java and Since we are building a CD pipeline, we should have some tests in place. Our code is so simple that it only needs one test case which is AppTest.java = Source code can be found in src.

The Docker File where we package our Application

The Dockerfile is a multistage one to keep the image size as small as possible. The Dockerfile is avaible in repository to view.

The Service Since we are using Kubernetes as the platform on which we host this application, we need at least a service and a deployment.

The deployment The application itself, once dockerized, can be deployed to Kubernetes through a Deployment resource. The deployment.yml file available in repositoty.

The Playbook

In this lab, we are using Ansible as our deployment tool. There are many other ways to deploy Kubernetes resources including Helm Charts, but we uses Ansible here. Ansible uses playbooks to organize its instructions. Our playbook.yml file placed in repository.

Ansible already includes the k8s module for handling communication with the Kubernetes API server. So, we don’t need kubectl installed but we do need a valid kubeconfig file for connecting to the cluster.

Step 02 :-

Install Jenkins, Ansible, and Docker Let’s install Ansible and use it to automatically deploy a Jenkins server and Docker runtime environment.

Step 03: Configuring Jenkins User To Connect To The Cluster Jenkins runs with jenkins user /home/jenkins/.kube/config kube config file is placed in above path.jenkins user have access to kubernetes cluster where it will deploy the apps.

Step 04: Create The Jenkins Pipeline Job

Create a new Jenkins job and select the Pipeline type. We used the Poll SCM as the build trigger; setting this option instructs Jenkins to check the Git repository on a periodic basis (every minute as indicated by * * * * *). If the repo has changed since the last poll, the job is triggered. In the pipeline itself, we specified the repository URL and the credentials. The branch is master. In this lab, we are adding all the job’s code in a Jenkinsfile that is stored in the same repository as the code.

Step 05: Configure Jenkins Credentials For GitHub and Docker Hub

Go to /credentials/store/system/domain/_/newCredentials and add the credentials to both targets.

Step 06: Create the kubernetes cluster

Kubernetes cluster is created in AWS using kops As shown below, cluster worker node and master is spread across mulitple AZ to avoid impact of AZ failure. As 3 master nodes are created,we will high availabilty if any of the master node is failed.

kops create cluster --kubernetes-version 1.15 --network-cidr 10.10.18.0/21 --vpc XXXXXXX --zones us-west-2d,us-west-2e,us-west-2f --bastion --topology=private --networking=weave --master-zones=us-west-2d,us-west-2e,us-west-2f --dns-zone=XXXXXX --name=kube.test.example.com --master-size=t2.medium --node-size=t2.medium --cloud=aws For details steps to create kubernetes cluster ,Please refer kubernetes_cluster_steps file.

Steps 07:Create deployment file and other resources

  7.1 Deployment file:

Image id is parameterized and latest build number is given as command line argument in ansible play book.

podAntiAffinity (topologyKey: kubernetes.io/hostname,topologyKey: failure-domain.beta.kubernetes.io/zone) is included to avoid more than one pod to be scedhuled in same hostname and AZ.Liveness and readiness probe are configured with 8080 port.

memory limit is specified as 2 GB ,even memory leak is happened due to the code issue, it will affect worker node where it is deployed

 7.2 other resources

kubernetes_app_HPA.yaml -->It will autoscale number of pods based on memory utilization

kubernetes_app_service.yaml--> application is exposed as load balancer and ssl is configured.

kubernetes_app_PDB.yaml--> PodDisruptionBudget is specified , at any given time maximum one pod can be unavailablee and at least one pod should be in available

kubernetes_external_dns.yaml-->Ext_DNS role have acess to Route53.external dns will update hostname entry in hosted zone

Step 08: Create the Jenkinsfile

The Jenkinsfile is what instructs Jenkins about how to build, test, dockerize, publish, and deliver our application. Jenkinsfile is available in repository to view.

Compile-Package stage

Build is taken using maven and packaged as jar file.

Build Docker Image stage

Image is created using docker file.docker file have steps to copy the jar file into base alphine and exposed in port 8080. Image is tagged with dockerhub userid and jenking build number.

Docker Image Push stage

Docker hub credential is configured in jenkins. Image is pushed to docker hub using that credentials.

Deploy stage

Docker image is deployed using ansible play book.Image id is passed as command line argument.

Step 09: Test Application

curl https://webapp-test.test.example.com:8080/