image-cloner
This is just an exercise.
It's a kubernetes controller that watches the Deployments and “caches” the images by re-uploading to your own registry repository and reconfiguring the applications to use these copies.
To configure the backup image registry you must specify the following environment variables:
| Variable | Description | Example |
|---|---|---|
| IMAGE_CLONER_REGISTRY | target registry | localhost:5000 |
| IMAGE_CLONER_USER | target registry login username | testuser |
| IMAGE_CLONER_PASS | target registry login password | testpass |
| IMAGE_CLONER_SKIP_NAMESPACES | namespaces to skip | ns1,...,nsN |
For example, an option could be saving:
Local development and testing
Clone this project
$ git clone https://github.com/lucasepe/image-cloner.git
Change directory to examples.
$ cd examples
Start KinD with a local docker registry enabled
$ make kind.up
when you are done, to destroy the cluster, type:
$ make kind.down
Run the controller
Go back to root folder:
$ cd ..
Run the controller:
$ go run cmd/main.go
You should see something like this:
2021-12-18T18:46:48.693+0100 INFO controller-runtime.metrics metrics server is starting to listen {"addr": ":8080"}
2021-12-18T18:46:48.693+0100 INFO setup starting manager
2021-12-18T18:46:48.693+0100 INFO controller-runtime.manager starting metrics server {"path": "/metrics"}
2021-12-18T18:46:48.693+0100 INFO controller.image-cloner Starting Controller
2021-12-18T18:46:48.693+0100 INFO controller.image-cloner Starting workers {"worker count": 1}
2021-12-18T18:46:48.693+0100 INFO controller-runtime.manager.controller.deployment Starting EventSource {"reconciler group": "apps", "reconciler kind": "Deployment", "source": "kind source: /, Kind="}
2021-12-18T18:46:48.693+0100 INFO controller-runtime.manager.controller.deployment Starting Controller {"reconciler group": "apps", "reconciler kind": "Deployment"}
2021-12-18T18:46:48.795+0100 INFO controller-runtime.manager.controller.deployment Starting workers {"reconciler group": "apps", "reconciler kind": "Deployment", "worker count": 1}
Create a deployment and watch the logs
$ kubectl apply -f examples/deploy-nginx.yml
As soon as the deployment will be ready, the controller will clone the image.
In the next iteration, during the reconciliation loop, the controller will realize that the image has already been cloned and will skip the backup.
2021-12-18T18:51:25.484+0100 DEBUG controller.image-cloner inspecting deployment {"name": "nginx", "namespace": "demo-system"}
2021-12-18T18:51:25.484+0100 DEBUG controller.image-cloner checking deployment container {"name": "nginx", "namespace": "demo-system", "image": "nginx:1.21.4-alpine"}
2021-12-18T18:51:25.484+0100 DEBUG controller.image-cloner cloning deployment image {"name": "nginx", "namespace": "demo-system", "image": "nginx:1.21.4-alpine"}
2021-12-18T18:51:32.077+0100 DEBUG controller.image-cloner updating deployment image {"name": "nginx", "namespace": "demo-system", "From": "nginx:1.21.4-alpine", "To": "localhost:5000/nginx:1.21.4-alpine"}
2021-12-18T18:51:32.086+0100 DEBUG controller.image-cloner deployment image reference updated {"name": "nginx", "namespace": "demo-system", "image": "localhost:5000/nginx:1.21.4-alpine"}
2021-12-18T18:51:32.086+0100 DEBUG controller.image-cloner inspecting deployment {"name": "nginx", "namespace": "demo-system"}
2021-12-18T18:51:32.086+0100 DEBUG controller.image-cloner checking deployment container {"name": "nginx", "namespace": "demo-system", "image": "localhost:5000/nginx:1.21.4-alpine"}
2021-12-18T18:51:32.086+0100 DEBUG controller.image-cloner image already cloned {"name": "nginx", "namespace": "demo-system", "image": "localhost:5000/nginx:1.21.4-alpine"}
Deploying this controller to your Kubernetes cluster
Deploy the RBAC
Since this controller must be able to update deployments in any namespace, it will at least need a cluster role that gives permissions to list, get and update those resources.
To apply RBAC, type:
$ kubectl apply -f examples/rbac.yml
Deploy the Controller
$ kubectl apply -f examples/image-cloner.yml
Watch the logs
Loook at the image-cloner-system namespace to find the pod name:
$ kubectl get pods -n image-cloner-system
Retrieve the controller log stream:
$ kubectl logs --follow -n image-cloner-system image-cloner
