website/v1.1/docs/user-guide/managing-deployments.md

layout, title

layout	title
docwithnav	Kubernetes User Guide: Managing Applications: Managing deployments

Kubernetes User Guide: Managing Applications: Managing deployments

You’ve deployed your application and exposed it via a service. Now what? Kubernetes provides a number of tools to help you manage your application deployment, including scaling and updating. Among the features we’ll discuss in more depth are configuration files and labels.

Table of Contents

• Kubernetes User Guide: Managing Applications: Managing deployments
  • Organizing resource configurations
  • Bulk operations in kubectl
  • Using labels effectively
  • Canary deployments
  • Updating labels
  • Scaling your application
  • Updating your application without a service outage
  • In-place updates of resources
  • Disruptive updates
  • What's next?

Organizing resource configurations

Many applications require multiple resources to be created, such as a Replication Controller and a Service. Management of multiple resources can be simplified by grouping them together in the same file (separated by --- in YAML). For example:

{% highlight yaml %} {% raw %} apiVersion: v1 kind: Service metadata: name: my-nginx-svc labels: app: nginx spec: type: LoadBalancer ports:

• port: 80 selector: app: nginx

---

apiVersion: v1 kind: ReplicationController metadata: name: my-nginx spec: replicas: 2 template: metadata: labels: app: nginx spec: containers: - name: nginx image: nginx ports: - containerPort: 80 {% endraw %} {% endhighlight %}

Multiple resources can be created the same way as a single resource:

{% highlight console %} {% raw %} $ kubectl create -f ./nginx-app.yaml services/my-nginx-svc replicationcontrollers/my-nginx {% endraw %} {% endhighlight %}

The resources will be created in the order they appear in the file. Therefore, it's best to specify the service first, since that will ensure the scheduler can spread the pods associated with the service as they are created by the replication controller(s).

kubectl create also accepts multiple -f arguments:

{% highlight console %} {% raw %} $ kubectl create -f ./nginx-svc.yaml -f ./nginx-rc.yaml {% endraw %} {% endhighlight %}

And a directory can be specified rather than or in addition to individual files:

{% highlight console %} {% raw %} $ kubectl create -f ./nginx/ {% endraw %} {% endhighlight %}

kubectl will read any files with suffixes .yaml, .yml, or .json.

It is a recommended practice to put resources related to the same microservice or application tier into the same file, and to group all of the files associated with your application in the same directory. If the tiers of your application bind to each other using DNS, then you can then simply deploy all of the components of your stack en masse.

A URL can also be specified as a configuration source, which is handy for deploying directly from configuration files checked into github:

{% highlight console %} {% raw %} $ kubectl create -f https://raw.githubusercontent.com/GoogleCloudPlatform/kubernetes/master/docs/user-guide/replication.yaml replicationcontrollers/nginx {% endraw %} {% endhighlight %}

Bulk operations in kubectl

Resource creation isn’t the only operation that kubectl can perform in bulk. It can also extract resource names from configuration files in order to perform other operations, in particular to delete the same resources you created:

{% highlight console %} {% raw %} $ kubectl delete -f ./nginx/ replicationcontrollers/my-nginx services/my-nginx-svc {% endraw %} {% endhighlight %}

In the case of just two resources, it’s also easy to specify both on the command line using the resource/name syntax:

{% highlight console %} {% raw %} $ kubectl delete replicationcontrollers/my-nginx services/my-nginx-svc {% endraw %} {% endhighlight %}

For larger numbers of resources, one can use labels to filter resources. The selector is specified using -l:

{% highlight console %} {% raw %} $ kubectl delete all -lapp=nginx replicationcontrollers/my-nginx services/my-nginx-svc {% endraw %} {% endhighlight %}

Because kubectl outputs resource names in the same syntax it accepts, it’s easy to chain operations using $() or xargs:

{% highlight console %} {% raw %} $ kubectl get $(kubectl create -f ./nginx/ | grep my-nginx) CONTROLLER CONTAINER(S) IMAGE(S) SELECTOR REPLICAS my-nginx nginx nginx app=nginx 2 NAME LABELS SELECTOR IP(S) PORT(S) my-nginx-svc app=nginx app=nginx 10.0.152.174 80/TCP {% endraw %} {% endhighlight %}

Using labels effectively

The examples we’ve used so far apply at most a single label to any resource. There are many scenarios where multiple labels should be used to distinguish sets from one another.

For instance, different applications would use different values for the app label, but a multi-tier application, such as the guestbook example, would additionally need to distinguish each tier. The frontend could carry the following labels:

{% highlight yaml %} {% raw %} labels: app: guestbook tier: frontend {% endraw %} {% endhighlight %}

while the Redis master and slave would have different tier labels, and perhaps even an additional role label:

{% highlight yaml %} {% raw %} labels: app: guestbook tier: backend role: master {% endraw %} {% endhighlight %}

and

{% highlight yaml %} {% raw %} labels: app: guestbook tier: backend role: slave {% endraw %} {% endhighlight %}

The labels allow us to slice and dice our resources along any dimension specified by a label:

{% highlight console %} {% raw %} $ kubectl create -f ./guestbook-fe.yaml -f ./redis-master.yaml -f ./redis-slave.yaml replicationcontrollers/guestbook-fe replicationcontrollers/guestbook-redis-master replicationcontrollers/guestbook-redis-slave $ kubectl get pods -Lapp -Ltier -Lrole NAME READY STATUS RESTARTS AGE APP TIER ROLE guestbook-fe-4nlpb 1/1 Running 0 1m guestbook frontend <n/a> guestbook-fe-ght6d 1/1 Running 0 1m guestbook frontend <n/a> guestbook-fe-jpy62 1/1 Running 0 1m guestbook frontend <n/a> guestbook-redis-master-5pg3b 1/1 Running 0 1m guestbook backend master guestbook-redis-slave-2q2yf 1/1 Running 0 1m guestbook backend slave guestbook-redis-slave-qgazl 1/1 Running 0 1m guestbook backend slave my-nginx-divi2 1/1 Running 0 29m nginx <n/a> <n/a> my-nginx-o0ef1 1/1 Running 0 29m nginx <n/a> <n/a> $ kubectl get pods -lapp=guestbook,role=slave NAME READY STATUS RESTARTS AGE guestbook-redis-slave-2q2yf 1/1 Running 0 3m guestbook-redis-slave-qgazl 1/1 Running 0 3m {% endraw %} {% endhighlight %}

Canary deployments

Another scenario where multiple labels are needed is to distinguish deployments of different releases or configurations of the same component. For example, it is common practice to deploy a canary of a new application release (specified via image tag) side by side with the previous release so that the new release can receive live production traffic before fully rolling it out. For instance, a new release of the guestbook frontend might carry the following labels:

{% highlight yaml %} {% raw %} labels: app: guestbook tier: frontend track: canary {% endraw %} {% endhighlight %}

and the primary, stable release would have a different value of the track label, so that the sets of pods controlled by the two replication controllers would not overlap:

{% highlight yaml %} {% raw %} labels: app: guestbook tier: frontend track: stable {% endraw %} {% endhighlight %}

The frontend service would span both sets of replicas by selecting the common subset of their labels, omitting the track label:

{% highlight yaml %} {% raw %} selector: app: guestbook tier: frontend {% endraw %} {% endhighlight %}

Updating labels

Sometimes existing pods and other resources need to be relabeled before creating new resources. This can be done with kubectl label. For example:

{% highlight console %} {% raw %} $ kubectl label pods -lapp=nginx tier=fe NAME READY STATUS RESTARTS AGE my-nginx-v4-9gw19 1/1 Running 0 14m NAME READY STATUS RESTARTS AGE my-nginx-v4-hayza 1/1 Running 0 13m NAME READY STATUS RESTARTS AGE my-nginx-v4-mde6m 1/1 Running 0 17m NAME READY STATUS RESTARTS AGE my-nginx-v4-sh6m8 1/1 Running 0 18m NAME READY STATUS RESTARTS AGE my-nginx-v4-wfof4 1/1 Running 0 16m $ kubectl get pods -lapp=nginx -Ltier NAME READY STATUS RESTARTS AGE TIER my-nginx-v4-9gw19 1/1 Running 0 15m fe my-nginx-v4-hayza 1/1 Running 0 14m fe my-nginx-v4-mde6m 1/1 Running 0 18m fe my-nginx-v4-sh6m8 1/1 Running 0 19m fe my-nginx-v4-wfof4 1/1 Running 0 16m fe {% endraw %} {% endhighlight %}

Scaling your application

When load on your application grows or shrinks, it’s easy to scale with kubectl. For instance, to increase the number of nginx replicas from 2 to 3, do:

{% highlight console %} {% raw %} $ kubectl scale rc my-nginx --replicas=3 scaled $ kubectl get pods -lapp=nginx NAME READY STATUS RESTARTS AGE my-nginx-1jgkf 1/1 Running 0 3m my-nginx-divi2 1/1 Running 0 1h my-nginx-o0ef1 1/1 Running 0 1h {% endraw %} {% endhighlight %}

Updating your application without a service outage

At some point, you’ll eventually need to update your deployed application, typically by specifying a new image or image tag, as in the canary deployment scenario above. kubectl supports several update operations, each of which is applicable to different scenarios.

To update a service without an outage, kubectl supports what is called “rolling update”, which updates one pod at a time, rather than taking down the entire service at the same time. See the rolling update design document and the example of rolling update for more information.

Let’s say you were running version 1.7.9 of nginx:

{% highlight yaml %} {% raw %} apiVersion: v1 kind: ReplicationController metadata: name: my-nginx spec: replicas: 5 template: metadata: labels: app: nginx spec: containers: - name: nginx image: nginx:1.7.9 ports: - containerPort: 80 {% endraw %} {% endhighlight %}

To update to version 1.9.1, you can use kubectl rolling-update --image:

{% highlight console %} {% raw %} $ kubectl rolling-update my-nginx --image=nginx:1.9.1 Creating my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 {% endraw %} {% endhighlight %}

In another window, you can see that kubectl added a deployment label to the pods, whose value is a hash of the configuration, to distinguish the new pods from the old:

{% highlight console %} {% raw %} $ kubectl get pods -lapp=nginx -Ldeployment NAME READY STATUS RESTARTS AGE DEPLOYMENT my-nginx-1jgkf 1/1 Running 0 1h 2d1d7a8f682934a254002b56404b813e my-nginx-ccba8fbd8cc8160970f63f9a2696fc46-k156z 1/1 Running 0 1m ccba8fbd8cc8160970f63f9a2696fc46 my-nginx-ccba8fbd8cc8160970f63f9a2696fc46-v95yh 1/1 Running 0 35s ccba8fbd8cc8160970f63f9a2696fc46 my-nginx-divi2 1/1 Running 0 2h 2d1d7a8f682934a254002b56404b813e my-nginx-o0ef1 1/1 Running 0 2h 2d1d7a8f682934a254002b56404b813e my-nginx-q6all 1/1 Running 0 8m 2d1d7a8f682934a254002b56404b813e {% endraw %} {% endhighlight %}

kubectl rolling-update reports progress as it progresses:

{% highlight console %} {% raw %} Updating my-nginx replicas: 4, my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 replicas: 1 At end of loop: my-nginx replicas: 4, my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 replicas: 1 At beginning of loop: my-nginx replicas: 3, my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 replicas: 2 Updating my-nginx replicas: 3, my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 replicas: 2 At end of loop: my-nginx replicas: 3, my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 replicas: 2 At beginning of loop: my-nginx replicas: 2, my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 replicas: 3 Updating my-nginx replicas: 2, my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 replicas: 3 At end of loop: my-nginx replicas: 2, my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 replicas: 3 At beginning of loop: my-nginx replicas: 1, my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 replicas: 4 Updating my-nginx replicas: 1, my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 replicas: 4 At end of loop: my-nginx replicas: 1, my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 replicas: 4 At beginning of loop: my-nginx replicas: 0, my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 replicas: 5 Updating my-nginx replicas: 0, my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 replicas: 5 At end of loop: my-nginx replicas: 0, my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 replicas: 5 Update succeeded. Deleting old controller: my-nginx Renaming my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 to my-nginx my-nginx {% endraw %} {% endhighlight %}

If you encounter a problem, you can stop the rolling update midway and revert to the previous version using --rollback:

{% highlight console %} {% raw %} $ kubectl kubectl rolling-update my-nginx --image=nginx:1.9.1 --rollback Found existing update in progress (my-nginx-ccba8fbd8cc8160970f63f9a2696fc46), resuming. Found desired replicas.Continuing update with existing controller my-nginx. Stopping my-nginx-02ca3e87d8685813dbe1f8c164a46f02 replicas: 1 -> 0 Update succeeded. Deleting my-nginx-ccba8fbd8cc8160970f63f9a2696fc46 my-nginx {% endraw %} {% endhighlight %}

This is one example where the immutability of containers is a huge asset.

If you need to update more than just the image (e.g., command arguments, environment variables), you can create a new replication controller, with a new name and distinguishing label value, such as:

{% highlight yaml %} {% raw %} apiVersion: v1 kind: ReplicationController metadata: name: my-nginx-v4 spec: replicas: 5 selector: app: nginx deployment: v4 template: metadata: labels: app: nginx deployment: v4 spec: containers: - name: nginx image: nginx:1.9.2 args: [“nginx”,”-T”] ports: - containerPort: 80 {% endraw %} {% endhighlight %}

and roll it out:

{% highlight console %} {% raw %} $ kubectl rolling-update my-nginx -f ./nginx-rc.yaml Creating my-nginx-v4 At beginning of loop: my-nginx replicas: 4, my-nginx-v4 replicas: 1 Updating my-nginx replicas: 4, my-nginx-v4 replicas: 1 At end of loop: my-nginx replicas: 4, my-nginx-v4 replicas: 1 At beginning of loop: my-nginx replicas: 3, my-nginx-v4 replicas: 2 Updating my-nginx replicas: 3, my-nginx-v4 replicas: 2 At end of loop: my-nginx replicas: 3, my-nginx-v4 replicas: 2 At beginning of loop: my-nginx replicas: 2, my-nginx-v4 replicas: 3 Updating my-nginx replicas: 2, my-nginx-v4 replicas: 3 At end of loop: my-nginx replicas: 2, my-nginx-v4 replicas: 3 At beginning of loop: my-nginx replicas: 1, my-nginx-v4 replicas: 4 Updating my-nginx replicas: 1, my-nginx-v4 replicas: 4 At end of loop: my-nginx replicas: 1, my-nginx-v4 replicas: 4 At beginning of loop: my-nginx replicas: 0, my-nginx-v4 replicas: 5 Updating my-nginx replicas: 0, my-nginx-v4 replicas: 5 At end of loop: my-nginx replicas: 0, my-nginx-v4 replicas: 5 Update succeeded. Deleting my-nginx my-nginx-v4 {% endraw %} {% endhighlight %}

You can also run the update demo to see a visual representation of the rolling update process.

In-place updates of resources

Sometimes it’s necessary to make narrow, non-disruptive updates to resources you’ve created. For instance, you might want to add an annotation with a description of your object. That’s easiest to do with kubectl patch:

{% highlight console %} {% raw %} $ kubectl patch rc my-nginx-v4 -p '{"metadata": {"annotations": {"description": "my frontend running nginx"}}}' my-nginx-v4 $ kubectl get rc my-nginx-v4 -o yaml apiVersion: v1 kind: ReplicationController metadata: annotations: description: my frontend running nginx ... {% endraw %} {% endhighlight %}

The patch is specified using json.

For more significant changes, you can get the resource, edit it, and then replace the resource with the updated version:

{% highlight console %} {% raw %} $ kubectl get rc my-nginx-v4 -o yaml > /tmp/nginx.yaml $ vi /tmp/nginx.yaml $ kubectl replace -f /tmp/nginx.yaml replicationcontrollers/my-nginx-v4 $ rm $TMP {% endraw %} {% endhighlight %}

The system ensures that you don’t clobber changes made by other users or components by confirming that the resourceVersion doesn’t differ from the version you edited. If you want to update regardless of other changes, remove the resourceVersion field when you edit the resource. However, if you do this, don’t use your original configuration file as the source since additional fields most likely were set in the live state.

Disruptive updates

In some cases, you may need to update resource fields that cannot be updated once initialized, or you may just want to make a recursive change immediately, such as to fix broken pods created by a replication controller. To change such fields, use replace --force, which deletes and re-creates the resource. In this case, you can simply modify your original configuration file:

{% highlight console %} {% raw %} $ kubectl replace -f ./nginx-rc.yaml --force replicationcontrollers/my-nginx-v4 replicationcontrollers/my-nginx-v4 {% endraw %} {% endhighlight %}

What's next?

• Learn about how to use kubectl for application introspection and debugging.
• Tips and tricks when working with config