Adding Callouts and Fixing Links (#64)
* Adding callouts and small edits for consistancy * fixing links * Updates per Ahmet Changed `Replicas` to replica field Gave excerpt highlighted syntax * Update README.md
This commit is contained in:
Cody Clark
Ahmet Alp Balkan
parent
d1cab528bd
commit
1fe5df1a6f
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@ -14,7 +14,7 @@ Deploying stateful distributed applications, like Cassandra, within a clustered
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**Cassandra Docker**
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The pods use the [```gcr.io/google-samples/cassandra:v12```](https://github.com/kubernetes/examples/blob/master/cassandra/image/Dockerfile)
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The Pods use the [`gcr.io/google-samples/cassandra:v12`](https://github.com/kubernetes/examples/blob/master/cassandra/image/Dockerfile)
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image from Google's [container registry](https://cloud.google.com/container-registry/docs/).
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The docker is based on `debian:jessie` and includes OpenJDK 8. This image includes a standard Cassandra installation from the Apache Debian repo. By using environment variables you can change values that are inserted into `cassandra.yaml`.
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@ -43,31 +43,30 @@ To complete this tutorial, you should already have a basic familiarity with [Pod
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* Have a supported Kubernetes Cluster running
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**Note:** Please read the [getting started guides](https://kubernetes.io/docs/setup/pick-right-solution/) if you do not already have a cluster.
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**Note:** Please read the [getting started guides](https://kubernetes.io/docs/setup/pick-right-solution/) if you do not already have a cluster.
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{: .note}
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### Additional Minikube Setup Instructions
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**Warning:** [Minikube](https://kubernetes.io/docs/getting-started-guides/minikube/) defaults to 1024MB of memory and 1 CPU which results in an insufficient resource errors.
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**Caution:** [Minikube](https://kubernetes.io/docs/getting-started-guides/minikube/) defaults to 1024MB of memory and 1 CPU which results in an insufficient resource errors during this tutorial.
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{: .caution}
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To avoid these errors, run minikube with:
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```
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minikube start --memory 5120 --cpus=4
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```
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minikube start --memory 5120 --cpus=4
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{% endcapture %}
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{% capture lessoncontent %}
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## Creating a Cassandra Headless Service
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A Kubernetes [Service](https://kubernetes.io/docs/concepts/services-networking/service/) describes a set of [Pods](https://kubernetes.io/docs/concepts/workloads/pods/pod/) that perform the same task.
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The following `Service` is used for DNS lookups between Cassandra pods and clients within the Kubernetes Cluster.
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The following `Service` is used for DNS lookups between Cassandra Pods and clients within the Kubernetes Cluster.
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1. `cd` to the folder you saved the .yaml files.
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2. Create a `Service` to track all Cassandra StatefulSet Nodes from the following `.yaml` file:
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1. Launch a terminal window in the directory you downloaded the manifest files.
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2. Create a `Service` to track all Cassandra StatefulSet Nodes from the `cassandra-service.yaml` file:
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```shell
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kubectl create -f cassandra-service.yaml
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```
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kubectl create -f cassandra-service.yaml
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{% include code.html language="yaml" file="cassandra-service.yaml" ghlink="/docs/tutorials/stateful-application/cassandra-service.yaml" %}
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@ -75,31 +74,26 @@ kubectl create -f cassandra-service.yaml
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Get the Cassandra `Service`.
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```shell
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kubectl get svc cassandra
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```
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kubectl get svc cassandra
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The response should be
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```console
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NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE
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cassandra None <none> 9042/TCP 45s
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```
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NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE
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cassandra None <none> 9042/TCP 45s
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If anything else returns, the service was not successfully created. Read [Debug Services](https://kubernetes.io/docs/tasks/debug-application-cluster/debug-service/) for common issues.
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## Using a StatefulSet to Create a Cassandra Ring
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The StatefulSet manifest, included below, creates a Cassandra ring that consists of three pods.
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The StatefulSet manifest, included below, creates a Cassandra ring that consists of three Pods.
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**Note:** This example uses the default provisioner for Minikube. Please update the following StatefulSet for the cloud you are working with.
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**Note:** This example uses the default provisioner for Minikube. Please update the following StatefulSet for the cloud you are working with.
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{: .note}
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1. Update the StatefulSet if necessary.
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2. Create the Cassandra StatefulSet from the following `.yaml` file:
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2. Create the Cassandra StatefulSet from the `cassandra-statefulset.yaml` file:
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```shell
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kubectl create -f cassandra-statefulset.yaml
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```
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kubectl create -f cassandra-statefulset.yaml
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{% include code.html language="yaml" file="cassandra-statefulset.yaml" ghlink="/docs/tutorials/stateful-application/cassandra-statefulset.yaml" %}
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@ -107,131 +101,115 @@ kubectl create -f cassandra-statefulset.yaml
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1. Get the Cassandra StatefulSet:
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```shell
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kubectl get statefulset cassandra
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```
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kubectl get statefulset cassandra
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The response should be
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```console
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NAME DESIRED CURRENT AGE
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cassandra 3 0 13s
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```
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NAME DESIRED CURRENT AGE
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cassandra 3 0 13s
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The StatefulSet resource deploys pods sequentially.
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The StatefulSet resource deploys Pods sequentially.
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{:start="2"}
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2. Get the Pods to see the ordered creation status:
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```shell
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kubectl get pods -l="app=cassandra"
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NAME READY STATUS RESTARTS AGE
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cassandra-0 1/1 Running 0 1m
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cassandra-1 0/1 ContainerCreating 0 8s
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```
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kubectl get pods -l="app=cassandra"
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The response should be
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NAME READY STATUS RESTARTS AGE
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cassandra-0 1/1 Running 0 1m
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cassandra-1 0/1 ContainerCreating 0 8s
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**Note:** It can take up to ten minutes for all three pods to deploy.
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**Note:** It can take up to ten minutes for all three Pods to deploy.
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{: .note}
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Once all pods are deployed, the same command returns:
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Once all Pods are deployed, the same command returns:
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```shell
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kubectl get pods -l="app=cassandra"
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NAME READY STATUS RESTARTS AGE
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cassandra-0 1/1 Running 0 10m
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cassandra-1 1/1 Running 0 9m
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cassandra-2 1/1 Running 0 8m
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```
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NAME READY STATUS RESTARTS AGE
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cassandra-0 1/1 Running 0 10m
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cassandra-1 1/1 Running 0 9m
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cassandra-2 1/1 Running 0 8m
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{:start="3"}
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3. Run the Cassandra utility nodetool to display the status of the ring.
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```
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kubectl exec cassandra-0 -- nodetool status
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```
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kubectl exec cassandra-0 -- nodetool status
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```console
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Datacenter: DC1-K8Demo
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======================
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Status=Up/Down
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|/ State=Normal/Leaving/Joining/Moving
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-- Address Load Tokens Owns (effective) Host ID Rack
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UN 10.4.2.4 65.26 KiB 32 63.7% a9d27f81-6783-461d-8583-87de2589133e Rack1-K8Demo
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UN 10.4.0.4 102.04 KiB 32 66.7% 5559a58c-8b03-47ad-bc32-c621708dc2e4 Rack1-K8Demo
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UN 10.4.1.4 83.06 KiB 32 69.6% 9dce943c-581d-4c0e-9543-f519969cc805 Rack1-K8Demo
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```
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The response is:
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Datacenter: DC1-K8Demo
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======================
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Status=Up/Down
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|/ State=Normal/Leaving/Joining/Moving
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-- Address Load Tokens Owns (effective) Host ID Rack
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UN 172.17.0.5 83.57 KiB 32 74.0% e2dd09e6-d9d3-477e-96c5-45094c08db0f Rack1-K8Demo
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UN 172.17.0.4 101.04 KiB 32 58.8% f89d6835-3a42-4419-92b3-0e62cae1479c Rack1-K8Demo
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UN 172.17.0.6 84.74 KiB 32 67.1% a6a1e8c2-3dc5-4417-b1a0-26507af2aaad Rack1-K8Demo
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## Modifying the Cassandra StatefulSet
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Use `kubectl edit` to modify the size of of a Cassandra StatefulSet.
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1. Run the following command:
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```shell
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kubectl edit statefulset cassandra
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```
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This command opens an editor in your terminal. The line you need to change is `Replicas`.
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kubectl edit statefulset cassandra
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This command opens an editor in your terminal. The line you need to change is the `replicas` field.
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**Note:** The following sample is an excerpt of the StatefulSet file.
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{: .note}
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```console
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# Please edit the object below. Lines beginning with a '#' will be ignored,
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# and an empty file will abort the edit. If an error occurs while saving this file will be
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# reopened with the relevant failures.
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#
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apiVersion: apps/v1beta1
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kind: StatefulSet
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metadata:
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creationTimestamp: 2016-08-13T18:40:58Z
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generation: 1
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labels:
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app: cassandra
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name: cassandra
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namespace: default
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resourceVersion: "323"
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selfLink: /apis/apps/v1beta1/namespaces/default/statefulsets/cassandra
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uid: 7a219483-6185-11e6-a910-42010a8a0fc0
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spec:
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replicas: 3
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```
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```yaml
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# Please edit the object below. Lines beginning with a '#' will be ignored,
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# and an empty file will abort the edit. If an error occurs while saving this file will be
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# reopened with the relevant failures.
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#
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apiVersion: apps/v1beta1
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kind: StatefulSet
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metadata:
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creationTimestamp: 2016-08-13T18:40:58Z
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generation: 1
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labels:
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app: cassandra
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name: cassandra
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namespace: default
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resourceVersion: "323"
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selfLink: /apis/apps/v1beta1/namespaces/default/statefulsets/cassandra
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uid: 7a219483-6185-11e6-a910-42010a8a0fc0
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spec:
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replicas: 3
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```
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{:start="2"}
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2. Increase the number of replicas to 4, and then save the manifest.
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2. Change the number of replicas to 4, and then save the manifest.
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The StatefulSet now contains 4 pods.
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The StatefulSet now contains 4 Pods.
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3. Get the Cassandra StatefulSet to verify:
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```shell
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kubectl get statefulset cassandra
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```
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kubectl get statefulset cassandra
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The response should be
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The response should be
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```console
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NAME DESIRED CURRENT AGE
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cassandra 4 4 36m
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```
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NAME DESIRED CURRENT AGE
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cassandra 4 4 36m
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{% endcapture %}
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{% capture cleanup %}
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Deleting or scaling a StatefulSet down does not delete the volumes associated with the StatefulSet. This ensures safety first: your data is more valuable than an auto purge of all related StatefulSet resources.
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**Warning:** Depending on the storage class and reclaim policy, deleting the Persistent Volume Claims may cause the associated volumes to also be deleted. Never assume you’ll be able to access data if its volume claims are deleted.
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**Warning:** Depending on the storage class and reclaim policy, deleting the Persistent Volume Claims may cause the associated volumes to also be deleted. Never assume you’ll be able to access data if its volume claims are deleted.
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{: .warning}
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1. Run the following commands to delete everything in a `StatefulSet`:
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```shell
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grace=$(kubectl get po cassandra-0 -o=jsonpath='{.spec.terminationGracePeriodSeconds}') \
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&& kubectl delete statefulset -l app=cassandra \
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&& echo "Sleeping $grace" \
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&& sleep $grace \
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&& kubectl delete pvc -l app=cassandra
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```
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grace=$(kubectl get po cassandra-0 -o=jsonpath='{.spec.terminationGracePeriodSeconds}') \
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&& kubectl delete statefulset -l app=cassandra \
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&& echo "Sleeping $grace" \
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&& sleep $grace \
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&& kubectl delete pvc -l app=cassandra
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2. Run the following command to delete the Cassandra `Service`.
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```shell
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kubectl delete service -l app=cassandra
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```
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kubectl delete service -l app=cassandra
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{% endcapture %}
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@ -29,12 +29,12 @@ This tutorial shows you how to build and deploy a simple, multi-tier web applica
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{% include task-tutorial-prereqs.md %}
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Download the following configuration files:
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1. [redis-master-deployment.yaml](https://kubernetes.io/docs/tutorials/docs/tutorials/stateless-application/guestbook/redis-master-deployment.yaml)
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1. [redis-master-service.yaml](https://kubernetes.io/docs/tutorials/docs/tutorials/stateless-application/guestbook/redis-master-service.yaml)
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1. [redis-slave-deployment.yaml](https://kubernetes.io/docs/tutorials/docs/tutorials/stateless-application/guestbook/redis-slave-deployment.yaml)
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1. [redis-slave-service.yaml](https://kubernetes.io/docs/tutorials/docs/tutorials/stateless-application/guestbook/redis-slave-service.yaml)
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1. [frontend-deployment.yaml](https://kubernetes.io/docs/tutorials/docs/tutorials/stateless-application/guestbook/frontend-deployment.yaml)
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1. [frontend-service.yaml](https://kubernetes.io/docs/tutorials/docs/tutorials/stateless-application/guestbook/frontend-service.yaml)
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1. [redis-master-deployment.yaml](https://kubernetes.io/docs/tutorials/stateless-application/guestbook/redis-master-deployment.yaml)
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1. [redis-master-service.yaml](https://kubernetes.io/docs/tutorials/stateless-application/guestbook/redis-master-service.yaml)
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1. [redis-slave-deployment.yaml](https://kubernetes.io/docs/tutorials/stateless-application/guestbook/redis-slave-deployment.yaml)
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1. [redis-slave-service.yaml](https://kubernetes.io/docs/tutorials/stateless-application/guestbook/redis-slave-service.yaml)
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1. [frontend-deployment.yaml](https://kubernetes.io/docs/tutorials/stateless-application/guestbook/frontend-deployment.yaml)
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1. [frontend-service.yaml](https://kubernetes.io/docs/tutorials/stateless-application/guestbook/frontend-service.yaml)
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{% endcapture %}
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