Docker contd
Containerization
- This refers to the process of running the application in containers
- This majorly means creating a Dockerfile for every application developed by your dev team
Case-Study: spring petclinic
- This is a sample java application
- Application download location Refer Here
- To run this application we need java 11 and 8080 port to access the application
- How this application is executed
Manual steps:
- Create an ubuntu linux vm and login into that
- Now install jdk 11
sudo apt update
sudo apt install openjdk-11-jdk -y
- Now download the application
cd /tmp
wget https://referenceapplicationskhaja.s3.us-west-2.amazonaws.com/spring-petclinic-2.4.2.jar
- Now to run the application
java -jar /tmp/spring-petclinic-2.4.2.jar
* Now access the application http://<public-ip>:8080
Problem statement
- We need to create a docker image for the application whenever there are code changes.
- The process
- cannot be manual
- has to simple
- supports making changes
- steps needs to be version controlled.
Docker Image information
- Docker hub has 3 types of images
- official images
- Verified Publisher
- Community Images
- Registries like DockerHub have repositories.
- Each Docker Image will have a Repository
- Docker image name convention
# for non official images
<username>/<repository>:<tag>
# for offical images
<repository>:<tag>
- Tag in Docker image represents a version.
- If the tag is not specified docker will replace tag with
latest
# image name
nginx
=> official repo => nginx
=> tag is latest
jenkins/jenkins:lts-jdk11
=> username = jenkins
=> repo => jenkins
=> tag => lts-jdk11
Port forwarding
- Overview
- Example:
docker container run -d --name mynginx -p 44444:80 nginx
Ways of Working Building Docker Images
- Choose the right base image
- Composing a Dockerfile
