GlusterFS: Improve role documentation

Signed-off-by: Jose A. Rivera <jarrpa@redhat.com>

inventory/byo/hosts.byo.native-glusterfs.example

@@ -0,0 +1,51 @@
+# This is an example of a bring your own (byo) host inventory for a cluster
+# with natively hosted, containerized GlusterFS storage.
+#
+# This inventory may be used with the byo/config.yml playbook to deploy a new
+# cluster with GlusterFS storage, which will use that storage to create a
+# volume that will provide backend storage for a hosted Docker registry.
+#
+# This inventory may also be used with byo/openshift-glusterfs/config.yml to
+# deploy GlusterFS storage on an existing cluster. With this playbook, the
+# registry backend volume will be created but the administrator must then
+# either deploy a hosted registry or change an existing hosted registry to use
+# that volume.
+#
+# There are additional configuration parameters that can be specified to
+# control the deployment and state of a GlusterFS cluster. Please see the
+# documentation in playbooks/byo/openshift-glusterfs/README.md and
+# roles/openshift_storage_glusterfs/README.md for additional details.
+
+[OSEv3:children]
+masters
+nodes
+# Specify there will be GlusterFS nodes
+glusterfs
+
+[OSEv3:vars]
+ansible_ssh_user=root
+deployment_type=origin
+# Specify that we want to use GlusterFS storage for a hosted registry
+openshift_hosted_registry_storage_kind=glusterfs
+
+[masters]
+master  node=True storage=True master=True
+
+[nodes]
+master  node=True storage=True master=True openshift_schedulable=False
+# A hosted registry, by default, will only be deployed on nodes labeled
+# "region=infra".
+node0   node=True openshift_node_labels="{'region': 'infra'}" openshift_schedulable=True
+node1   node=True openshift_node_labels="{'region': 'infra'}" openshift_schedulable=True
+node2   node=True openshift_node_labels="{'region': 'infra'}" openshift_schedulable=True
+
+# Specify the glusterfs group, which contains the nodes that will host
+# GlusterFS storage pods. At a minimum, each node must have a
+# "glusterfs_devices" variable defined. This variable is a list of block
+# devices the node will have access to that is intended solely for use as
+# GlusterFS storage. These block devices must be bare (e.g. have no data, not
+# be marked as LVM PVs), and will be formatted.
+[glusterfs]
+node0  glusterfs_devices='[ "/dev/vdb", "/dev/vdc", "/dev/vdd" ]'
+node1  glusterfs_devices='[ "/dev/vdb", "/dev/vdc", "/dev/vdd" ]'
+node2  glusterfs_devices='[ "/dev/vdb", "/dev/vdc", "/dev/vdd" ]'

inventory/byo/hosts.origin.example

@@ -438,9 +438,6 @@ openshift_master_identity_providers=[{'name': 'htpasswd_auth', 'login': 'true',
 #openshift_hosted_registry_storage_openstack_volumeID=3a650b4f-c8c5-4e0a-8ca5-eaee11f16c57
 #openshift_hosted_registry_storage_volume_size=10Gi
 #
-# Native GlusterFS Registry Storage
-#openshift_hosted_registry_storage_kind=glusterfs
-#
 # AWS S3
 # S3 bucket must already exist.
 #openshift_hosted_registry_storage_kind=object

inventory/byo/hosts.ose.example

@@ -438,9 +438,6 @@ openshift_master_identity_providers=[{'name': 'htpasswd_auth', 'login': 'true',
 #openshift_hosted_registry_storage_openstack_volumeID=3a650b4f-c8c5-4e0a-8ca5-eaee11f16c57
 #openshift_hosted_registry_storage_volume_size=10Gi
 #
-# Native GlusterFS Registry Storage
-#openshift_hosted_registry_storage_kind=glusterfs
-#
 # AWS S3
 #
 # S3 bucket must already exist.

roles/openshift_storage_glusterfs/README.md

@@ -8,10 +8,18 @@ Requirements
 
 * Ansible 2.2
 
+Host Groups
+-----------
+
+The following group is expected to be populated for this role to run:
+
+* `[glusterfs]`
+
 Role Variables
 --------------
 
-From this role:
+This role has the following variables that control the integration of a
+GlusterFS cluster into a new or existing OpenShift cluster:
 
 | Name                                             | Default value           |                                         |
 |--------------------------------------------------|-------------------------|-----------------------------------------|
@@ -47,6 +55,7 @@ Example Playbook
   hosts: oo_first_master
   roles:
   - role: openshift_storage_glusterfs
+    when: groups.oo_glusterfs_to_config | default([]) | count > 0
 ```
 
 License