Add external LB management handler hook interface

Based on conversation on an ansible issue[1], I implemented
a LB orchestration role[2] similar to the POC here[3].

This will allow external loadbalancer management roles to hook
into a universal notify listener "Manage LB" to perform before/
after endpoint management actions when the service is being
restarted.

[1]: https://github.com/ansible/ansible/issues/27813
[2]: https://github.com/Logan2211/ansible-haproxy-endpoints
[3]: https://github.com/Logan2211/tmp-ansible-27813

Change-Id: I19818234d9c8a5ad90b6387c360d598fda03a65e

doc/source/index.rst

@@ -47,6 +47,19 @@ Example playbook
 .. literalinclude:: ../../examples/playbook.yml
    :language: yaml
 
+External Restart Hooks
+~~~~~~~~~~~~~~~~~~~~~~
+
+When the role performs a restart of the service, it will notify an Ansible
+handler named ``Manage LB``, which is a noop within this role. In the
+playbook, other roles may be loaded before and after this role which will
+implement Ansible handler listeners for ``Manage LB``, allowing external roles
+to manage the load balancer endpoints responsible for sending traffic to the
+servers being restarted by marking them in maintenance or active mode,
+draining sessions, etc. For an example implementation, please reference the
+`ansible-haproxy-endpoints role <https://github.com/Logan2211/ansible-haproxy-endpoints>`_
+used by the openstack-ansible project.
+
 Tags
 ~~~~
 
@@ -56,4 +69,3 @@ The ``cinder-install`` tag can be used to install and upgrade.
 
 The ``cinder-config`` tag can be used to maintain configuration of the
 service.
-

handlers/main.yml

@@ -67,3 +67,7 @@
     enabled: yes
     state: restarted
     daemon_reload: "{{ (ansible_service_mgr == 'systemd') | ternary('yes', omit) }}"
+
+- meta: noop
+  listen: Manage LB
+  when: false

tasks/cinder_init_systemd.yml

@@ -50,6 +50,7 @@
     group: "root"
   with_items: "{{ filtered_cinder_services }}"
   notify:
+    - Manage LB
     - Restart cinder services
 
 - name: Place the systemd init script
@@ -63,4 +64,5 @@
     config_type: "ini"
   with_items: "{{ filtered_cinder_services }}"
   notify:
+    - Manage LB
     - Restart cinder services

tasks/cinder_install.yml

@@ -80,7 +80,9 @@
     dest: "{{ cinder_bin | dirname }}"
     copy: "no"
   when: cinder_get_venv | changed
-  notify: Restart cinder services
+  notify:
+    - Manage LB
+    - Restart cinder services
 
 - name: Install pip packages
   pip:
@@ -97,7 +99,9 @@
   retries: 5
   delay: 2
   when: cinder_get_venv | failed or cinder_get_venv | skipped
-  notify: Restart cinder services
+  notify:
+    - Manage LB
+    - Restart cinder services
 
 - name: Remove python from path first (CentOS, openSUSE)
   file:

tasks/cinder_post_install.yml

@@ -40,6 +40,7 @@
       config_overrides: "{{ cinder_policy_overrides }}"
       config_type: "json"
   notify:
+    - Manage LB
     - Restart cinder services
 
 - name: Copy cinder configs
@@ -51,6 +52,7 @@
   with_fileglob:
     - rootwrap.d/*
   notify:
+    - Manage LB
     - Restart cinder services
 
 - name: Ensure cinder tgt include

tasks/cinder_uwsgi.yml

@@ -29,4 +29,5 @@
   with_items: "{{ filtered_cinder_services }}"
   when: item.wsgi_app | default(False)
   notify:
+    - Manage LB
     - Restart cinder services