- Ensure you're logged in with correct AWS account first (with
$ aws configure) $ aws eks --region {aws-region} update-kubeconfig --name {cluster-name}
View all contexts available:
$ kubectl config get-contexts
Switch to the specific context:
$ kubectl config use-context arn:aws:eks:{aws-region}:{aws-account-id}:cluster/{cluster-name}
$ kubectl config set-context --current --namespace=learning-hour
You can use this command to switch to any named namespace that you have access to.
$ kubectl get namespaces
Deployment — the configuration of the running application on the cluster. Controls & manages the actual pods and containers.
$ kubectl get deployments
You should see something like:
NAME READY UP-TO-DATE AVAILABLE AGE
hello-world-deployment 1/1 1 1 8m31s
$ kubectl describe deployment hello-world-deployment
You should see something like:
Name: hello-world-deployment
Namespace: learning-hour
CreationTimestamp: Mon, 05 Sep 2022 09:32:41 +0200
Labels: app=hello-world
Annotations: deployment.kubernetes.io/revision: 1
Selector: app=hello-world
Replicas: 1 desired | 1 updated | 1 total | 1 available | 0 unavailable
StrategyType: RollingUpdate
MinReadySeconds: 0
RollingUpdateStrategy: 25% max unavailable, 25% max surge
Pod Template:
Labels: app=hello-world
Containers:
server:
Image: tddfellow/nodejs-hello-world:latest
Port: 8080/TCP
Host Port: 0/TCP
Environment:
PORT: 8080
Mounts: <none>
Volumes: <none>
Conditions:
Type Status Reason
---- ------ ------
Available True MinimumReplicasAvailable
Progressing True NewReplicaSetAvailable
OldReplicaSets: <none>
NewReplicaSet: hello-world-deployment-7c76b9b7f4 (1/1 replicas created)
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal ScalingReplicaSet 9m13s deployment-controller Scaled up replica set hello-world-deployment-7c76b9b7f4 to 1
Pod — an actual instance of the application running on the cluster. It can have 1 or more docker containers running inside of it.
$ kubectl get pods
You should see something like:
NAME READY STATUS RESTARTS AGE
hello-world-deployment-7c76b9b7f4-xcl48 1/1 Running 0 10m
The part 7c76b9b7f4-xcl48 might differ. When deployment restarts the pod it generates a new unique value every time.
$ kubectl describe pod {pod-name}
Usually, you have to copy the pod name from the pod list.
You should see something like this:
Name: hello-world-deployment-7c76b9b7f4-xcl48
Namespace: learning-hour
Priority: 0
Node: ip-##-##-##-###.############.compute.internal/##.##.##.###
Start Time: Mon, 05 Sep 2022 09:32:41 +0200
Labels: app=hello-world
pod-template-hash=7c76b9b7f4
Annotations: kubernetes.io/psp: eks.privileged
Status: Running
IP: ##-##-##-###
IPs:
IP: ##-##-##-###
Controlled By: ReplicaSet/hello-world-deployment-7c76b9b7f4
Containers:
server:
Container ID: docker:https://##############################################
Image: tddfellow/nodejs-hello-world:latest
Image ID: docker-pullable:https://tddfellow/nodejs-hello-world@sha256:##############################################
Port: 8080/TCP
Host Port: 0/TCP
State: Running
Started: Mon, 05 Sep 2022 09:32:47 +0200
Ready: True
Restart Count: 0
Environment:
PORT: 8080
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-45rpb (ro)
Conditions:
Type Status
Initialized True
Ready True
ContainersReady True
PodScheduled True
Volumes:
default-token-45rpb:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-45rpb
Optional: false
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 13m default-scheduler Successfully assigned learning-hour/hello-world-deployment-7c76b9b7f4-xcl48 to ip-##-##-##-###.###########.compute.internal
Normal Pulling 12m kubelet Pulling image "tddfellow/nodejs-hello-world:latest"
Normal Pulled 12m kubelet Successfully pulled image "tddfellow/nodejs-hello-world:latest" in 4.385947268s
Normal Created 12m kubelet Created container server
Normal Started 12m kubelet Started container server
Output the latest logs just once and exit:
$ kubectl logs {pod-name}
Follow (or tail) the logs continuously (until interrupted with CTRL+C):
$ kubectl logs --follow {pod-name}
You should see something like this:
yarn run v1.22.19
$ node ./hello-world.js
Listening on port :8080
received GET /hello with name=world
If the pod for some reason becomes unresponsive, you may want to kill it:
$ kubectl delete pod {pod-name}
You should see the following output:
pod "hello-world-deployment-7c76b9b7f4-xcl48" deleted
However, if you list the pods again (kubectl get pods), you'll see that the pod is back up again under different name. That's a deployment ensuring that there is at least minimum number of instances of your application.
Important note: killing pod in such a manner may cause downtime. It's a very abrupt way to restart the pod.
If you have a deployment ensuring 2 or more instances, then you can perform a much safer restart (without or close to without any downtime):
$ kubectl rollout restart deployment hello-world-deployment
It will start the new instance(s) first, and then kill the old one(s). If you do kubectl get pods shortly after, you should see something like this:
NAME READY STATUS RESTARTS AGE
hello-world-deployment-58f747644d-2xzcr 1/1 Running 0 8s
hello-world-deployment-7c76b9b7f4-l2f56 0/1 Terminating 0 2m46s
Let's say, something isn't working and you're struggling to identify why. Last resort would be to drop into the pod's shell and start investigating why. You can do this with the following command:
$ kubectl exec -it {pod-name} -- sh
In a pinch, this can be used to run scripts from inside of the container:
/app # node example-script.js
If you've done everything correctly, you should see the following output:
Congratulations! You've run the example script successfully!
/app #
Service — an exposed container port (not necessarily to the world, but at least to other containers of the cluster, and some AWS resources.
$ kubectl get services
You should see something like this:
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
hello-world-service ClusterIP 172.20.76.241 <none> 8080/TCP,9090/TCP 37m
$ kubectl describe service hello-world-service
You should see something like this:
Name: hello-world-service
Namespace: learning-hour
Labels: app=hello-world
Annotations: <none>
Selector: app=hello-world
Type: ClusterIP
IP Families: <none>
IP: ###.##.##.###
IPs: ###.##.##.###
Port: http 8080/TCP
TargetPort: 8080/TCP
Endpoints: ###.##.##.###:8080
Port: secret 9090/TCP
TargetPort: 9090/TCP
Endpoints: ###.##.##.###:9090
Session Affinity: None
Events: <none>
The example application has 2 ports, one public and one "secret." The secret port can be used only by internal parts of the cloud. You can also gain temporary access to this secret port via port-forwarding:
$ kubectl port-forward service/hello-world-service 9090:9090
And then try accessing http:https://localhost:9090/secret. You should see:
{"message":"this is a secret endpoint!"}
You can stop port-forwarding by interrupting the kubectl port-forward process with CTRL+C.