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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

DevOps Stages

  • There are 4 stages:

    DevOps Stages

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

    Pipeline

  • 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

CICD-1

CICD-2

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

  • 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

    Docker-1

    Docker-2

Project or Job

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

  • Job and project used interchangeably

    Project/Job

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.

    Post Build Actions

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

  • Parameters and environment variables :

    Post Build Actions

    @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:
    Format
  • 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