kube-exec-controller is an admission controller for handling container drift (caused by kubectl exec, attach, cp, or other interactive requests) inside a Kubernetes cluster. It runs as a Deployment and can be referred in a ValidatingWebhookConfiguration (see the provided demo/ as an example) to detect and evict interacted Pods after a pre-defined interval. This project also includes a kubectl plugin, named kubectl-pi (pod-interaction), for checking such interacted Pods or extending their eviction time.
Here is an overview of running a kubectl exec command in a K8s cluster with this admission controller service enabled:
If you have a local K8s cluster up running, you can deploy kube-exec-controller and apply its validating admission webhooks simply by:
$ git clone git@github.com:box/kube-exec-controller.git
$ cd kube-exec-controller
$ make deploy
You should get a demo app and its admission webhooks deployed after the above make deploy command completes:
$ kubectl get pod,service -n kube-exec-controller
NAME READY STATUS RESTARTS AGE
pod/demo-deploy-5d5cd95f94-jwf5b 1/1 Running 0 9s
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/demo-service ClusterIP 10.96.211.63 <none> 443/TCP 9s
$ kubectl get ValidatingWebhookConfiguration
NAME WEBHOOKS AGE
demo-validating-webhook-config 2 24s
To see how kube-exec-controller works, let's create a test Pod in your local cluster and send a kubectl exec request to it:
$ kubectl run test --image=nginx
pod/test created
$ kubectl exec test -- touch new-file
You will see the test Pod has some labels attached and receives corresponding K8s events from our controller app:
$ kubectl get pod --show-labels
NAME READY STATUS RESTARTS AGE LABELS
test 1/1 Running 0 2s box.com/podInitialInteractionTimestamp=1634408037,box.com/podInteractorUsername=kubernetes-admin,box.com/podTTLDuration=2m0s,run=test
$ kubectl describe pod test
...
Warning PodInteraction 20s kube-exec-controller Pod was interacted with 'kubectl exec/attach' command by a user 'kubernetes-admin' initially at time 2021-10-16 18:04:44.5257517 +0000 UTC m=+27.185038701
Warning PodInteraction 21s kube-exec-controller Pod will be evicted at time 2021-10-16 18:06:44 +0000 UTC (in about 1m59s)
You can also utilize the kubectl pi plugin to get more detailed info or request an extension to the test Pod's eviction time:
$ kubectl pi get
POD-NAME INTERACTOR POD-TTL EXTENSION EXTENSION-REQUESTER EVICTION-TIME
test kubernetes-admin 2m0s 2021-10-16 18:06:44 +0000 UTC
$ kubectl pi extend --duration=1m
Successfully extended the termination time of pod/test with a duration=1m
$ kubectl pi get
POD-NAME INTERACTOR POD-TTL EXTENSION EXTENSION-REQUESTER EVICTION-TIME
test kubernetes-admin 2m0s 1m kubernetes-admin 2021-10-16 18:07:44 +0000 UTC
$ kubectl describe pod test
...
Warning PodInteraction 30s kube-exec-controller Pod eviction time has been extended by '1m', as requested from user 'kubernetes-admin'. New eviction time: 2021-10-16 18:07:44 +0000 UTC
Warning PodInteraction 30s kube-exec-controller Pod will be evicted at time 2021-10-16 18:07:44 +0000 UTC (in about 2m21s)
$ kube-exec-controller --help
Usage of kube-exec-controller:
-api-server string
URL to K8s api-server, required if kube-proxy is not set up
-cert-path string
Path to the PEM-encoded TLS certificate
-extend-chan-size int
Buffer size of the channel for handling Pod extension (default 500)
-interact-chan-size int
Buffer size of the channel for handling Pod interaction (default 500)
-key-path string
Path to the un-encrypted TLS key
-log-level debug
Log level. debug, `info`, `warn`, `error` are currently supported (default "info")
-namespace-allowlist string
Comma separated list of namespaces that allow interaction without evicting their Pods
-port int
Port for the app to listen on (default 8443)
-ttl-seconds int
TTL (time-to-live) of interacted Pods before getting evicted by the controller (default 600)
$ kubectl pi --help
Get pod interaction info or request an extension of its termination time
Usage:
kubectl pi [command] [flags]
Examples:
# get interaction info of specified pod(s)
kubectl pi get <pod-name-1> <pod-name-2> <...> -n POD_NAMESPACE
# get interaction info of all pods under the given namespace
kubectl pi get -n <pod-namespace> --all
# extend termination time of interacted pod(s)
kubectl pi extend -d <duration> <pod-name-1> <pod-name-2> <...> -n POD_NAMESPACE
# extend termination time of all interacted pods under the given namespace
kubectl pi extend -d <duration> -n <pod-namespace> --all
Flags:
-a, --all if present, select all pods under specified namespace (and ignore any given pod podName)
--cluster string The name of the kubeconfig cluster to use
--context string The name of the kubeconfig context to use
-d, --duration string a relative duration such as 5s, 2m, or 3h, default to 30m (default "30m")
-h, --help help for kubectl
-n, --namespace string If present, the namespace scope for this CLI request
...
Refer to CONTRIBUTING.md
Copyright 2021 Box, Inc. All rights reserved.
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.