fix wordpress tutorial pvcs #6418

msau42 · 2017-11-23T00:43:34Z

Use the default storageclass instead of pre-provisioned hostpath PVs

Fixes kubernetes/kubernetes#52441

This change is

msau42 · 2017-11-23T00:43:51Z

/assign @foxish @saad-ali

k8sio-netlify-preview-bot · 2017-11-23T00:45:35Z

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steveperry-53 · 2017-11-28T00:34:08Z

@foxish @saad-ali Can one of you do a tech review for this? Thanks.

msau42 · 2017-11-28T00:58:38Z

I'm contemplating whether I should actually get rid of the statically created hostpath PVs altogether, and just use the default storageclass to provision the volume. WDYT?

tengqm · 2017-11-28T01:19:47Z

@msau42 Avoiding explicit setting of storage class unless you have a good reason,.. is this the encouraged practice?

msau42 · 2017-11-28T01:31:40Z

sounds good, I'll change it to just use default storage class then. Just wondering if we have any reason to keep the original behavior of using static hostpath PVs, which is now broken.

msau42 · 2017-11-28T20:15:35Z

Revamped to use the default storage class. This needs a lot of review. I had to add a lot of text about dynamic provisioning and default storage classes.

davidz627 · 2017-11-29T18:48:03Z

docs/tutorials/stateful-application/mysql-wordpress-persistent-volume.md


-### Setting up a hostPath Volume
+Many cluster environments have a default StorageClass installed.  When a StorageClass is not specified in the PersistentVolumeClaim, the cluster's default StorageClass is used instead.


quick link or note on "how to not use default storage class"? It's not always clear that in order to stop dynamic provisioning sometimes you have to make the SC=""

It is explained in detail in the PVC page.

jingxu97 · 2017-11-29T18:55:47Z

docs/tutorials/stateful-application/mysql-wordpress-persistent-volume.md

@@ -7,7 +7,7 @@ approvers:
 {% capture overview %}
 This tutorial shows you how to deploy a WordPress site and a MySQL database using Minikube. Both applications use PersistentVolumes and PersistentVolumeClaims to store data. 

-A [PersistentVolume](/docs/concepts/storage/persistent-volumes/) (PV) is a piece of storage in the cluster that has been provisioned by an administrator, and a [PersistentVolumeClaim](/docs/concepts/storage/persistent-volumes/#persistentvolumeclaims) (PVC) is a set amount of storage in a PV. PersistentVolumes and PersistentVolumeClaims are independent from Pod lifecycles and preserve data through restarting, rescheduling, and even deleting Pods. 
+A [PersistentVolume](/docs/concepts/storage/persistent-volumes/) (PV) is a piece of storage in the cluster that has been provisioned by an administrator, and a [PersistentVolumeClaim](/docs/concepts/storage/persistent-volumes/#persistentvolumeclaims) (PVC) is a set amount of storage in a PV. PersistentVolumes and PersistentVolumeClaims are independent from Pod lifecycles and preserve data through restarting, rescheduling, and even deleting Pods.  PersistentVolumes can be automatically provisioned by Kubernetes using a [StorageClass](/docs/concepts/storage/storage-classes/).


Not your change. But I feel the explanation of PVC and PV is not very clear.

a PVC is "a set amount of storage in a PV"?

PV is a piece of storage in the cluster has been provisioned by an administrator, or automatically provisioned by Kubernetes using a [StorageClass]?

+1 especially about point 1.

Another possibility:

"PV is a piece of storage in the cluster that has been provisioned (either manually by an administrator, or automatically by Kubernetes using a [StorageClass]). PVC is ..."

Updated. How about now?

steveperry-53 · 2017-11-29T19:03:29Z

This has tech approval from @tengqm. Waiting for resolution of concerns raised by @jingxu97.

verult · 2017-11-29T20:57:43Z

docs/tutorials/stateful-application/mysql-wordpress-persistent-volume.md

@@ -7,7 +7,7 @@ approvers:
 {% capture overview %}
 This tutorial shows you how to deploy a WordPress site and a MySQL database using Minikube. Both applications use PersistentVolumes and PersistentVolumeClaims to store data. 

-A [PersistentVolume](/docs/concepts/storage/persistent-volumes/) (PV) is a piece of storage in the cluster that has been provisioned by an administrator, and a [PersistentVolumeClaim](/docs/concepts/storage/persistent-volumes/#persistentvolumeclaims) (PVC) is a set amount of storage in a PV. PersistentVolumes and PersistentVolumeClaims are independent from Pod lifecycles and preserve data through restarting, rescheduling, and even deleting Pods. 
+A [PersistentVolume](/docs/concepts/storage/persistent-volumes/) (PV) is a piece of storage in the cluster that has been provisioned by an administrator, and a [PersistentVolumeClaim](/docs/concepts/storage/persistent-volumes/#persistentvolumeclaims) (PVC) is a set amount of storage in a PV. PersistentVolumes and PersistentVolumeClaims are independent from Pod lifecycles and preserve data through restarting, rescheduling, and even deleting Pods.  PersistentVolumes can be automatically provisioned by Kubernetes using a [StorageClass](/docs/concepts/storage/storage-classes/).


Another possibility:

"PV is a piece of storage in the cluster that has been provisioned (either manually by an administrator, or automatically by Kubernetes using a [StorageClass]). PVC is ..."

verult · 2017-11-29T21:04:25Z

docs/tutorials/stateful-application/mysql-wordpress-persistent-volume.md

-       kubectl get pv
-
-   The response should be like this:
+**Note:** If you are bringing up a cluster that needs to use the `hostPath` provisioner, the `--enable-hostpath-provisioner` flag must be set in the `controller-manager` component.


It's not trivial to set controller-manager flags. Is this set by default?

It is not set by default because hostpath provisioners are only meant for development/local clusters and should not be used in production.

If you use local-up.sh, there is a parameter that you can pass that will set the flag for you. But I'm not sure if we should be prescribing any specific cluster deployment methods in this tutorial.

verult · 2017-11-29T21:16:52Z

docs/tutorials/stateful-application/mysql-wordpress-persistent-volume.md


-**Warning:** Only use `hostPath` for developing and testing. With hostPath, your data lives on the node the Pod is scheduled onto and does not move between nodes. If a Pod dies and gets scheduled to another node in the cluster, the data is lost. 
+**Warning:** In local clusters, the default StorageClass uses the `hostPath` provisioner.  `hostPath` volumes are only suitable for development and testing. With `hostPath` volumes, your data lives on the node the Pod is scheduled onto and does not move between nodes. If a Pod dies and gets scheduled to another node in the cluster, the data is lost.


What's the default hostPath path? It may be a problem if the node filesystem is partially write-protected, but including the path here is good enough IMO.

/tmp/hostpath_pv/

hostpath provisioner is only for dev/local clusters, so I don't think we need to worry about node OSes here. If you run this tutorial in GCE, it will use the gce-pd provisioner, and not the hostpath provisioner.

I'll add a note here that the provisioner will create a directory under /tmp, so the data is definitely not in a permanent location.

jingxu97 · 2017-12-01T20:15:46Z

/lgtm

msau42 · 2017-12-12T03:37:14Z

@steveperry-53 would you be able to do a docs review?

msau42 · 2018-01-02T18:46:27Z

ping @steveperry-53 could you find someone to help do a docs review?

msau42 · 2018-01-03T22:55:28Z

/assign @steveperry-53

k8s-ci-robot added cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. labels Nov 23, 2017

k8s-ci-robot assigned foxish and saad-ali Nov 23, 2017

steveperry-53 added the Needs Tech Review label Nov 28, 2017

msau42 force-pushed the fix-wordpress-tutorial branch from f00a25f to f134d91 Compare November 28, 2017 20:10

k8s-ci-robot added size/L Denotes a PR that changes 100-499 lines, ignoring generated files. and removed size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. labels Nov 28, 2017

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fix wordpress tutorial pvcs

0cccf26

msau42 force-pushed the fix-wordpress-tutorial branch from f134d91 to 0cccf26 Compare November 29, 2017 23:10

k8s-ci-robot assigned jingxu97 Dec 1, 2017

k8s-ci-robot added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Dec 1, 2017

k8s-ci-robot assigned steveperry-53 Jan 3, 2018

tengqm merged commit 7d7c5a1 into kubernetes:master Jan 4, 2018

msau42 deleted the fix-wordpress-tutorial branch February 9, 2018 01:34

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fix wordpress tutorial pvcs #6418

fix wordpress tutorial pvcs #6418

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msau42 commented Jan 3, 2018


		### Setting up a hostPath Volume
		Many cluster environments have a default StorageClass installed. When a StorageClass is not specified in the PersistentVolumeClaim, the cluster's default StorageClass is used instead.


		Warning: Only use `hostPath` for developing and testing. With hostPath, your data lives on the node the Pod is scheduled onto and does not move between nodes. If a Pod dies and gets scheduled to another node in the cluster, the data is lost.
		Warning: In local clusters, the default StorageClass uses the `hostPath` provisioner. `hostPath` volumes are only suitable for development and testing. With `hostPath` volumes, your data lives on the node the Pod is scheduled onto and does not move between nodes. If a Pod dies and gets scheduled to another node in the cluster, the data is lost.

fix wordpress tutorial pvcs #6418

fix wordpress tutorial pvcs #6418

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