141 lines
4.4 KiB
Markdown
141 lines
4.4 KiB
Markdown
---
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title: Run a Stateless Application Using a Deployment
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---
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{% capture overview %}
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This page shows how to run an application using a Kubernetes Deployment object.
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{% endcapture %}
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{% capture objectives %}
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* Create an nginx deployment.
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* Use kubectl to list information about the deployment.
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* Update the deployment.
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{% endcapture %}
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{% capture prerequisites %}
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{% include task-tutorial-prereqs.md %}
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{% endcapture %}
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{% capture lessoncontent %}
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## Creating and exploring an nginx deployment
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You can run an application by creating a Kubernetes Deployment object, and you
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can describe a Deployment in a YAML file. For example, this YAML file describes
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a Deployment that runs the nginx:1.7.9 Docker image:
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{% include code.html language="yaml" file="deployment.yaml" ghlink="/docs/tasks/run-application/deployment.yaml" %}
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1. Create a Deployment based on the YAML file:
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kubectl create -f https://k8s.io/docs/tasks/run-application/deployment.yaml
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1. Display information about the Deployment:
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kubectl describe deployment nginx-deployment
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user@computer:~/kubernetes.github.io$ kubectl describe deployment nginx-deployment
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Name: nginx-deployment
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Namespace: default
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CreationTimestamp: Tue, 30 Aug 2016 18:11:37 -0700
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Labels: app=nginx
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Selector: app=nginx
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Replicas: 2 updated | 2 total | 2 available | 0 unavailable
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StrategyType: RollingUpdate
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MinReadySeconds: 0
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RollingUpdateStrategy: 1 max unavailable, 1 max surge
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Conditions:
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Type Status Reason
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---- ------ ------
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Available True MinimumReplicasAvailable
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OldReplicaSets: <none>
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NewReplicaSet: nginx-deployment-1771418926 (2/2 replicas created)
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No events.
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1. List the pods created by the deployment:
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kubectl get pods -l app=nginx
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NAME READY STATUS RESTARTS AGE
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nginx-deployment-1771418926-7o5ns 1/1 Running 0 16h
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nginx-deployment-1771418926-r18az 1/1 Running 0 16h
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1. Display information about a pod:
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kubectl describe pod <pod-name>
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where `<pod-name>` is the name of one of your pods.
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## Updating the deployment
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You can update the deployment by applying a new YAML file. This YAML file
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specifies that the deployment should be updated to use nginx 1.8.
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{% include code.html language="yaml" file="deployment-update.yaml" ghlink="/docs/tutorials/stateless-application/deployment-update.yaml" %}
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1. Apply the new YAML file:
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kubectl apply -f https://k8s.io/docs/tutorials/stateless-application/deployment-update.yaml
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1. Watch the deployment create pods with new names and delete the old pods:
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kubectl get pods -l app=nginx
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## Scaling the application by increasing the replica count
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You can increase the number of pods in your Deployment by applying a new YAML
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file. This YAML file sets `replicas` to 4, which specifies that the Deployment
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should have four pods:
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{% include code.html language="yaml" file="deployment-scale.yaml" ghlink="/docs/tutorials/stateless-application/deployment-scale.yaml" %}
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1. Apply the new YAML file:
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kubectl apply -f https://k8s.io/docs/tutorials/stateless-application/deployment-scale.yaml
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1. Verify that the Deployment has four pods:
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kubectl get pods -l app=nginx
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The output is similar to this:
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NAME READY STATUS RESTARTS AGE
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nginx-deployment-148880595-4zdqq 1/1 Running 0 25s
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nginx-deployment-148880595-6zgi1 1/1 Running 0 25s
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nginx-deployment-148880595-fxcez 1/1 Running 0 2m
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nginx-deployment-148880595-rwovn 1/1 Running 0 2m
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## Deleting a deployment
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Delete the deployment by name:
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kubectl delete deployment nginx-deployment
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## ReplicationControllers -- the Old Way
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The preferred way to create a replicated application is to use a Deployment,
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which in turn uses a ReplicaSet. Before the Deployment and ReplicaSet were
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added to Kubernetes, replicated applications were configured by using a
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[ReplicationController](/docs/concepts/workloads/controllers/replicationcontroller/).
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{% endcapture %}
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{% capture whatsnext %}
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* Learn more about [Deployment objects](/docs/concepts/workloads/controllers/deployment/).
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{% endcapture %}
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{% include templates/tutorial.md %}
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