Skip to content

Latest commit

 

History

History
155 lines (122 loc) · 6.46 KB

README.md

File metadata and controls

155 lines (122 loc) · 6.46 KB
Raw

Deployment

Deployments are intended to replace Replication Controllers. They provide the same replication functions (through Replica Sets) and also the ability to rollout changes and roll them back if necessary.

A deployment is a supervisor for pods, giving you fine-grained control over how and when a new pod version is rolled out as well as rolled back to a previous state.

Let’s create a deployment with a single container based on nginx:1.7.9 image, that supervises two replicas of a pod as well as a replica set:

$ kubectl apply -f nginx1.7.9-deployment.yaml
deployment.apps/nginx-deployment created

You can have a look at the deployment, as well as the the replica set and the pods the deployment looks after like so:

$ kubectl get deployments 
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment   2/2     3            3           49s

$ kubectl get rs
NAME                          DESIRED   CURRENT   READY   AGE
nginx-deployment-5754944d6c   2         2         2       3m28s

$kubectl get pods
NAME                                READY   STATUS    RESTARTS   AGE
nginx-deployment-5754944d6c-8f669   1/1     Running   0          3m54s
nginx-deployment-5754944d6c-g46jw   1/1     Running   0          3m54s

Let's update the deployment with a container based on nginx:latest image.

$ kubectl apply -f nginx_latest-deployment.yaml
deployment.apps/nginx-deployment configured

If you type get pods, you may see the old deployment instances still running while the new deployment is creating the container

$ kubectl get pods
NAME                                READY   STATUS              RESTARTS   AGE
nginx-deployment-5754944d6c-g46jw   1/1     Running             0          10m
nginx-deployment-698c64b949-6pbgq   1/1     Running             0          11s
nginx-deployment-698c64b949-vl29q   0/1     ContainerCreating   0          10s

After a while, old pod instances are terminating, the new onces are already running

$ kubectl get pods
NAME                                READY   STATUS        RESTARTS   AGE
nginx-deployment-5754944d6c-g46jw   0/1     Terminating   0          11m
nginx-deployment-698c64b949-6pbgq   1/1     Running       0          45s
nginx-deployment-698c64b949-vl29q   1/1     Running       0          44s

At the end, pod instances stay running, the old ones are not deployed anymore

$ kubectl get pods
NAME                                READY   STATUS    RESTARTS   AGE
nginx-deployment-698c64b949-6pbgq   1/1     Running   0          72s
nginx-deployment-698c64b949-vl29q   1/1     Running   0          71s

Also, a new replica set has been created by the deployment:

$ kubectl get rs
NAME                          DESIRED   CURRENT   READY   AGE
nginx-deployment-5754944d6c   0         0         0       17m
nginx-deployment-698c64b949   2         2         2       7m23s

Note that during the deployment you can check the progress using kubectl rollout status deploy/nginx-deployment

$ kubectl rollout status deploy/nginx-deployment
deployment "nginx-deployment" successfully rolled out

A history of all deployments is available via:

$ kubectl rollout history deploy/nginx-deployment
deployment.extensions/nginx-deployment 
REVISION  CHANGE-CAUSE
1         <none>
2         <none>

If there are problems in the deployment Kubernetes will automatically roll back to the previous version, however you can also explicitly roll back to a specific revision, as in our case to revision 1 (the original pod version):

$ kubectl rollout undo deploy/nginx-deployment --to-revision=1
deployment.extensions/nginx-deployment rolled back

$ kubectl rollout history deploy/nginx-deployment
deployment.extensions/nginx-deployment 
REVISION  CHANGE-CAUSE
2         <none>
3         <none>

At this point in time we’re back at where we started

What if we want to manually scale this deployment with replica = 10?

$ kubectl scale --replicas=10 deployment/nginx-deployment
deployment.extensions/nginx-deployment scaled

Verify the pods scaling

$ kubectl get pods
NAME                                READY   STATUS    RESTARTS   AGE
nginx-deployment-5754944d6c-2hrtr   1/1     Running   0          19s
nginx-deployment-5754944d6c-5c8sk   1/1     Running   0          19s
nginx-deployment-5754944d6c-5msgp   1/1     Running   0          4m33s
nginx-deployment-5754944d6c-d5qw2   1/1     Running   0          19s
nginx-deployment-5754944d6c-fp6rb   1/1     Running   0          19s
nginx-deployment-5754944d6c-grfgc   1/1     Running   0          19s
nginx-deployment-5754944d6c-kpkbb   1/1     Running   0          19s
nginx-deployment-5754944d6c-mgdp5   1/1     Running   0          4m31s
nginx-deployment-5754944d6c-rjv8h   1/1     Running   0          19s
nginx-deployment-5754944d6c-rzn2j   1/1     Running   0          19s

Let's verify how pods have been balanced between nodes

$ kubectl get pods -o wide
NAME                                READY   STATUS    RESTARTS   AGE   IP            NODE    NOMINATED NODE   READINESS GATES
nginx-deployment-5754944d6c-298qd   1/1     Running   0          12s   10.244.1.15   node1   <none>           <none>
nginx-deployment-5754944d6c-4tv4w   1/1     Running   0          7s    10.244.1.18   node1   <none>           <none>
nginx-deployment-5754944d6c-86tnb   1/1     Running   0          7s    10.244.1.19   node1   <none>           <none>
nginx-deployment-5754944d6c-czzq5   1/1     Running   0          12s   10.244.2.13   node2   <none>           <none>
nginx-deployment-5754944d6c-gjv4j   1/1     Running   0          7s    10.244.2.17   node2   <none>           <none>
nginx-deployment-5754944d6c-hbqbt   1/1     Running   0          7s    10.244.1.17   node1   <none>           <none>
nginx-deployment-5754944d6c-hrzct   1/1     Running   0          7s    10.244.2.16   node2   <none>           <none>
nginx-deployment-5754944d6c-k9cdl   1/1     Running   0          7s    10.244.1.16   node1   <none>           <none>
nginx-deployment-5754944d6c-wm5dk   1/1     Running   0          7s    10.244.2.15   node2   <none>           <none>
nginx-deployment-5754944d6c-xkqjg   1/1     Running   0          7s    10.244.2.14   node2   <none>           <none>

Finally, to clean up, we remove the deployment and with it the replica sets and pods it supervises:

$ kubectl delete deploy nginx-deployment
deployment.extensions "nginx-deployment" deleted

$ kubectl get pods
No resources found.