What happens to old image in ECR with latest tag when I push a new image with same tag?

Question

So, I was new to ECR/ECR I already pushed an image to my repo with latest tag. But what happens when I push another image with latest tag to the same repo? Will the old one tag changes because I want them to be there. Also, I can't change the tag every time as I wrote a pipeline as below. Do we have to redeploy the image to ECS? Or is it done automatically when we push new image to ECR ?

stage('docker image') {
            steps {
                   sh  ''' #!/bin/bash
                    set -x
                    cd $WORKDIR/search-adapter-service
                    if [[ -f "/home/jenkins/.m2/settings.xml" ]]
                    then
                       mv /home/jenkins/.m2/settings.xml /home/jenkins/.m2/settings.xml_back
                    fi
                    
                    $WORKDIR/apache-maven-3.6.3/bin/mvn clean install                    
                    '''
                    dir("$WORKDIR/search-adapter-service"){
                      script{
                         sh(script: "sudo docker build -t ${DOCKER_REGISTRY_REPO}:latest .")
                         sh(script: "sudo docker push ${DOCKER_REGISTRY_REPO}:latest")

1.I am expecting to it change the tag automatically for the old image. 2. Will it automatically also deploy to ECS? once we push? Or do we need to do it manually? If it can be automated. How do we achieve that?

Answer 1

The old image with the latest tag will sill be in ECR, it will just have the latest tag removed from it. If it had other tags it would still be accessible by those other tags. If it didn't have other tags, you would have to use the docker image ID (digest) to address it. All this is visible in the ECR web console.

ECS will not automatically deploy when you push a new image to ECR. You will need to trigger an ECS deployment via the command:

aws ecs update-service --cluster <cluster> --service <service> --force-new-deployment