CICD (Jenkins) Basics

What is DevOps?

• DevOps is a software development approach which involves Continuous Development, Continuous testing, Continuous Integration, Continuous Deployment and Continuous Monitoring throughout its development lifecycle.

  

DevOps Stages

• There are 4 stages:

  

• Pipeline is a logical step or a series of steps which define how software development lifecycle occurs

  

• Integration means putting all the code together from all the contributing developers and then merging the code and building it as whole.

• We call it continuous integration because everything happens in DevOps continuously.

• For Creating Pipeline in Jenkins we can have 3 jobs:
  • To build the project
  • To test the project
  • To deploy the project

What is CI and CD?

• CI/CD, which stands for continuous integration (CI) and continuous delivery (CD)

CI - Continuous Integration :

• A process where team members integrate their work continuously in a shared repository. Best achieved using some SCM tools like GIT.
• Can be daily or as needed Every integration or check-in in the repo is validated by automated build, automated by unit or integration tests

CD - Continuous Delivery :

• After the CI process, Deploying on a Prod like env and running automation tests to ensure the build is ready for release.

• Ensure the build is always in a Deployment state.

• Pre-prod or staging environment: exactly same as prod env, to make sure anything not crash in prod env, first deploy change in pre-prod/staging env.

CD - Continuous Deployment :

• Automated Deployment to Prod. Every change that passes through Automation Tests is deployed to Production

Jenkins - The ultimate CI Tool

• Jenkins is an open source automation tool written in Java with plugins built for Continuous Integration purpose. Plugins allows integration of various DevOps stages.

  

• Jenkins is a tool for continuous integration, Jenkins role is only till the application is packaged, now if it has to be delivered then we need some tools to deliver that product.

• Once the product/software moves on to the staging server to deploy it, we need tools like docker.

• Installing Jenkins on Windows : https://github.com/LinkedInLearning/learning-jenkins-3003221/tree/01_02
  • Need to install Java (OpenJDK), Git, before installing Jenkins.
• Plugins: A software package that extends Jenkins’ core functionality.

What is Docker

• Docker file builds a Docker image and that image contains all the project’s code
• We can run that image to create as many docker containers as we want

• Then this Image can be uploaded on Docker hub, from Docker hub any one can pull the image and build a container

  

  

Project or Job

• A user-configured description of the work that Jenkins will manage.

• Job and project used interchangeably

  

Artifacts

• Most jenkings jobs will generate some sort of products at the end of each build.
• It can be compiled executable like and .exe, an archive like a jar file or it might even be a report in the text file.

• These products are referred to as artifacts.

  

• ** - this tells jenkins to search for the file in the workspace without giving the exact path.

• Parameters and environment variables :

  

  @echo off
  @echo ENVIRONMENT = %ENVIRONMENT%

Scheduling Jobs :

• Updating software
• Monitoring system details
• Downloading and processing data
• Similar to Cron :
  • A time-based job scheduler in Unix-like operating systems
  • Jenkins uses a format similar to cron for scheduling jobs
  • Execution times are defined by an expression representing the schedule

Jenkins Scheduler Format& Aliases :

• Jenkins Scheduler Format is as follows:
  
• Use H for hashed values to spread out jobs around the desired time
• Use simple aliases for general times
  • @hourly
  • @daily
  • @midnight (To run any time after 12AM and before 3AM)
  • @weekly
  • @annualy

Time Zones :

• Time zones are relative to the server
• Many servers use the Universal Time, UTC time zone
  • If our Local time and the server time are different, make sure we account for that in our schedule.
• Plan your schedule accordingly

Views and Folder :

Views :

• Views provide a way of associating jobs on the dashboard and displaying them together.
• Views display jobs that meet a criteria
• Views are like a filter
• If we delete a view, all content inside will remain as it is.

Folders :

• Folders allow us to create structures that are very similar to file systems on a disk
• Folders group things together
• Folders contain jobs, views, and other folders
• Folders provide a namespace that is separate from other folders in jenkins
• If we delete a folder, all content inside will also got deleted.

Pipelines :

• Jenkins also allows us to configure jobs as code (instead of Jenkins user interface).
• These types of jobs are called pipelines.
• Stored in a file named Jenkinsfile
• Can be versioned in a code repository
• Configure Jenkins jobs

• Contain stages and steps

• Pipeline stages: Stages are sections of the pipeline

    pipeline {
        stages{
            stage ('Build') {
                Steps {
                    Echo "Checking out code…"
                }
                Steps {
                    Echo "Compiling code…"
                }
            }
            stage ('Test') {
            }
            stage ('Deploy') {
            }
        }
    }
  

  • Each stage must have a step, like build stage can have pull code from git
  • Steps are the actions to take

References

• [CI CD Pipeline Using Jenkins

  Continuous Integration and Deployment

  DevOps Tutorial

  Edureka](https://www.youtube.com/watch?v=m0a2CzgLNsc&ab_channel=edureka%21)

• https://www.linkedin.com/learning/learning-jenkins-14423877
• https://github.com/LinkedInLearning/learning-jenkins-3003221
• https://github.com/managedkaos/apache-maven-hello-world
• https://www.jenkins.io