In order to deploy a Java application into AWS ECS (Elastic Container Service) using Terraform, we need to consider a few different things.
Step 1 - Java Application
Create a file called HelloWorld.java and add the following code to it:
public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello, World!");
}
}
We now need to build our class as follows:
javac HelloWorld.java
Once this is done, we can package our application into a jar file:
jar cvf my-app.jar HelloWorld.class
Step 2 - Dockerfile
Next create a file called Dockerfile and copy the following code into it:
FROM openjdk:11-jre-slim
WORKDIR /app
COPY target/my-app.jar /app
CMD ["java", "-jar", "my-app.jar"]
Note that target/my-app.jar in this code is the relative path from the Dockerfile to the my-app.jar that we packaged in step 1 above.
Step 3 - Terraform
Next we will focus on the Terraform. To do this, we can either create different Terraform files, but in this example, we will simply create a single file called main.tf.
In this file, we will first create an ECS task definition:
resource "aws_ecs_task_definition" "my_task_definition" {
family = "my-task-definition"
container_definitions = jsonencode([
{
name = "my-container"
image = "my-docker-image"
cpu = 256
memory = 512
portMappings = [
{
containerPort = 8080
hostPort = 8080
}
]
}
])
}
Followed by an ECS service:
resource "aws_ecs_service" "my_service" {
name = "my-service"
cluster = aws_ecs_cluster.my_cluster.id
task_definition = aws_ecs_task_definition.my_task_definition.arn
desired_count = 1
network_configuration {
subnets = [aws_subnet.my_subnet.id]
security_groups = [aws_security_group.my_security_group.id]
assign_public_ip = true
}
}
Step 4 - Running the Terraform
Now we need to run the Terraform code, which we can do from the terminal as follows:
terraform init
terraform apply