Show image tags for each revisions of Kubernetes deployments

Oct 16, 2020 · 2 min read · kubectl kubernetes  ·
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One of the useful and powerful function is the roll back for me. Basically, all applications on our cluster are deployed automatically by CodePipeline in AWS but if some trouble happen, rolling back to the previous version is one of our options. At that time, all I have to do is the following command.

1$ kubectl rollout undo deployment my-app

When I execute the following command, the list of the revisions which are still remaining on the database on the Kubernetes cluster will be displayed.

1$ kubectl rollout history deployment my-app

The command’s response is:

 1REVISION  CHANGE-CAUSE
 229        <none>
 330        <none>
 431        <none>
 532        <none>
 633        <none>
 734        <none>
 835        <none>
 936        <none>
1037        <none>
1138        <none>
1239        <none>

And then, if the application should be rolled back to the specific revisions, the following command will work.

1$ kubectl rollout undo deployment my-app --to-revision=35

However, I want to know which image was used for each revision because we use the date string like "yyyymmddHHMMSS" for image tags as I posted before.

Docker: What’s better image tag than latest, none, and versions?

So, If I can see the list of revision numbers and image tags will be helpful for me. However, there’s no function in the kubectl command so I made a shell script like this.

 1#!/bin/bash
 2deployment_name=${1:-NONE}
 3
 4if [ $deployment_name == NONE ];then
 5    echo "USAGE: $0 DEPLOYMENT_NAME"
 6    exit 1
 7fi
 8
 9resource_name=`kubectl rollout history deployment $deployment_name -o name`
10echo "Resource name: $resource_name"
11for rev in `kubectl rollout history $resource_name | egrep '^[0-9]+' | awk '{print $1}'`
12do
13    image=`kubectl rollout history $resource_name --revision=${rev} | grep Image: | awk '{print $2}'`
14    printf "%02d : %s\n" $rev $image
15done

And its response is like this.

 1Resource name: deployment.apps/my-app
 232 : my-registry/my-app:202010061110
 333 : my-registry/my-app:202010070906
 434 : my-registry/my-app:202010080051
 535 : my-registry/my-app:202010080202
 637 : my-registry/my-app:202010130703
 738 : my-registry/my-app:202010130728
 839 : my-registry/my-app:202010080300
 940 : my-registry/my-app:202010130754
1041 : my-registry/my-app:202010130823
1142 : my-registry/my-app:202010130823
1243 : my-registry/my-app:202010130940

As a result of this, I can choose the relevant revision by the deployment date.