DevOps Classroomnotes 08/Nov/2022

Activity 1: Containerize the Java (Spring boot) Application

• Spring boot: This helps in building web based java applications with built in middleware
• Generally to extension of the java package is jar to run the spring boot application the command is java -jar <package>.jar
• Lets try to run an application spring pet clinic
• To run this application we need java 11
• when we run this application it exposes port 8080
• Manual steps

sudo apt update
sudo apt install openjdk-11-jdk -y 
java -version
wget https://referenceapplicationskhaja.s3.us-west-2.amazonaws.com/spring-petclinic-2.4.2.jar
java -jar spring-petclinic-2.4.2.jar

• To access the petclinic application navigate to http://<publicip-vm>:8080
  

Creating a container image using Dockerfile – Approach 1

• Refer Here for all the Dockerfile instructions
• For this activity lets stick closer to manual approach
  • Pick a base image => ubuntu:22.04
  • spring petclinic runs on port 8080
  • Steps to install are
    bash
sudo apt update
sudo apt install openjdk-11-jdk -y
wget https://referenceapplicationskhaja.s3.us-west-2.amazonaws.com/spring-petclinic-2.4.2.jar
  • steps to start application => java -jar spring-petclinic-2.4.2.jar
• On a highlevel to choose a base image instruction is FROM Refer Here
• To execute any commands to install/configure application the instruction is RUN Refer Here
• To expose the port command is EXPOSE Refer Here
• To start the application when container is created the instruction is CMD Refer Here
• Lets try to write a Dockerfile

FROM ubuntu:22.04
RUN apt update
RUN apt install openjdk-11-jdk wget -y
RUN wget https://referenceapplicationskhaja.s3.us-west-2.amazonaws.com/spring-petclinic-2.4.2.jar
EXPOSE 8080
CMD ["java", "-jar", "/spring-petclinic-2.4.2.jar"]

• Now create a new folder and a file with Dockerfile as a name and cpy the above contents. Create the docker image

docker image build -t spc_one:1.0 .
docker image ls

* Lets create a container in a detached mode with name processone

docker container run -d --name processone -p 8081:8080 spc_one:1.0

* Now access the application http://<vm-ip>:8081

Approach 2:

• To run spring pet clinic i need java 11, but in the previous image i have started from ubuntu which is not necessary
• Lets use amazon correto Refer Here
• ADD instruction is used to copy the files into images

FROM amazoncorretto:11
ADD https://referenceapplicationskhaja.s3.us-west-2.amazonaws.com/spring-petclinic-2.4.2.jar /spring-petclinic-2.4.2.jar
EXPOSE 8080
CMD ["java", "-jar", "/spring-petclinic-2.4.2.jar"]

• Build the image docker image build -t spc_two:1.0 .
• list the images
  
• Create the container docker container run --name processtwo -d -P spc_two:1.0
  
• Now access the application
  
• Generally all the image publisher have slim options which further reduces the size of container on disk
• Exercise: Try using amazoncorreto:11-alpine-jdk as base image and build spc_three

Exercise

• Refer Here for game of life
• To run this application we need tomcat 9 or 8 with java 8
• This application runs on port 8080 => http://<public-vm>:<port>/gameoflife
• Steps:

# copy the gameoflife.war into webapps folder of tomcat