Adds support for specifying GID AND UID for cinder system user

Change-Id: I141509b9e2fdb132357542c6b5204ffaa6f33d56

defaults/main.yml

@@ -79,6 +79,18 @@ cinder_system_comment: cinder system user
 cinder_system_shell: /bin/false
 cinder_system_home_folder: "/var/lib/{{ cinder_system_user_name }}"
 
+## Manually specified cinder UID/GID
+# Deployers can specify a UID for the cinder user as well as the GID for the
+# cinder group if needed. This is commonly used in environments where shared
+# storage is used, such as NFS or GlusterFS, and cinder UID/GID values must be
+# in sync between multiple servers.
+#
+# WARNING: Changing these values on an existing deployment can lead to
+#          failures, errors, and instability.
+#
+# cinder_system_user_uid = <UID>
+# cinder_system_group_gid = <GID>
+
 cinder_lock_path: /var/lock/cinder
 
 ## Cinder Auth

doc/source/configure-cinder.rst

@@ -627,3 +627,27 @@ the desired qos spec dictionary.
       options:
         consumer: front-end
         write_iops_sec: 100
+
+Shared storage and synchronized UID/GID
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Specify a custom UID for the cinder user and GID for the cinder group
+to ensure they are identical on each host. This is helpful when using shared
+storage on Compute nodes because it allows instances to migrate without
+filesystem ownership failures.
+
+By default, Ansible creates the cidner user and group without specifying the
+UID or GID. To specify custom values for the UID or GID, set the following
+Ansible variables:
+
+.. code-block:: yaml
+
+    cinder_system_user_uid = <specify a UID>
+    cinder_system_group_gid = <specify a GID>
+
+.. warning::
+
+    Setting this value after deploying an environment with
+    OpenStack-Ansible can cause failures, errors, and general instability. These
+    values should only be set once before deploying an OpenStack environment
+    and then never changed.

releasenotes/notes/gid-and-uid-cinder-system-user-support-f69b87b4876c0dd8.yaml

@@ -0,0 +1,5 @@
+---
+other:
+  - Added support for specifying GID and UID for cinder system user by defining
+    ``cinder_system_user_uid`` and ``cinder_system_group_gid``. This setting is
+    optional.

tasks/cinder_pre_install.yml

@@ -16,12 +16,14 @@
 - name: create the system group
   group:
     name: "{{ cinder_system_group_name }}"
+    gid: "{{ cinder_system_group_gid|default(omit) }}"
     state: "present"
     system: "yes"
 
 - name: Create the cinder system user
   user:
     name: "{{ cinder_system_user_name }}"
+    uid: "{{ cinder_system_user_uid|default(omit) }}"
     group: "{{ cinder_system_group_name }}"
     comment: "{{ cinder_system_comment }}"
     shell: "{{ cinder_system_shell }}"