From 902e638d956c858808d9084469b728df359385ec Mon Sep 17 00:00:00 2001
From: Logan V <logan2211@gmail.com>
Date: Sat, 16 Sep 2017 14:23:03 -0500
Subject: [PATCH] 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: I5aecc26606f41bc6b27fbe9a5f600914a88ff2c7
---
 doc/source/index.rst                      | 13 +++++++++++++
 handlers/main.yml                         |  4 ++++
 tasks/consoles/nova_console_novnc_ssl.yml |  4 +++-
 tasks/nova_init_systemd.yml               |  2 ++
 tasks/nova_install.yml                    |  8 ++++++--
 tasks/nova_post_install.yml               |  8 ++++++--
 tasks/nova_uwsgi.yml                      |  1 +
 7 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/doc/source/index.rst b/doc/source/index.rst
index 210ff805..29cf26c7 100644
--- a/doc/source/index.rst
+++ b/doc/source/index.rst
@@ -31,6 +31,19 @@ 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
 ~~~~
 
diff --git a/handlers/main.yml b/handlers/main.yml
index 9b4bd038..2b81ca57 100644
--- a/handlers/main.yml
+++ b/handlers/main.yml
@@ -74,3 +74,7 @@
     - "'nova_compute' in group_names"
     - "nova_discover_hosts_in_cells_interval | int < 1"
   listen: "Restart nova services"
+
+- meta: noop
+  listen: Manage LB
+  when: false
diff --git a/tasks/consoles/nova_console_novnc_ssl.yml b/tasks/consoles/nova_console_novnc_ssl.yml
index c9ea4bf2..1a5fdb6e 100644
--- a/tasks/consoles/nova_console_novnc_ssl.yml
+++ b/tasks/consoles/nova_console_novnc_ssl.yml
@@ -39,6 +39,8 @@
   with_items:
     - { content: "{{ nova_console_user_ssl_combined.stdout ~ '\n' }}", dest: "{{ nova_console_ssl_cert }}", mode: "0644" }
     - { src: "{{ nova_console_user_ssl_key }}", dest: "{{ nova_console_ssl_key }}", mode: "0640" }
-  notify: Restart nova services
+  notify:
+    - Manage LB
+    - Restart nova services
   tags:
     - nova-config
diff --git a/tasks/nova_init_systemd.yml b/tasks/nova_init_systemd.yml
index fd5c72bc..618366f2 100644
--- a/tasks/nova_init_systemd.yml
+++ b/tasks/nova_init_systemd.yml
@@ -49,6 +49,7 @@
     group: "root"
   with_items: "{{ filtered_nova_services }}"
   notify:
+    - Manage LB
     - Restart nova services
 
 - name: Place the systemd init script
@@ -62,4 +63,5 @@
     config_type: "ini"
   with_items: "{{ filtered_nova_services }}"
   notify:
+    - Manage LB
     - Restart nova services
diff --git a/tasks/nova_install.yml b/tasks/nova_install.yml
index b9d73a25..94d42b8e 100644
--- a/tasks/nova_install.yml
+++ b/tasks/nova_install.yml
@@ -118,7 +118,9 @@
     copy: "no"
   when:
     - nova_get_venv | changed
-  notify: Restart nova services
+  notify:
+    - Manage LB
+    - Restart nova services
   tags:
     - nova-pip-packages
 
@@ -138,7 +140,9 @@
   delay: 2
   when:
     - nova_get_venv | failed or nova_get_venv | skipped
-  notify: Restart nova services
+  notify:
+    - Manage LB
+    - Restart nova services
   tags:
     - nova-pip-packages
 
diff --git a/tasks/nova_post_install.yml b/tasks/nova_post_install.yml
index 3821b800..49ffa2cc 100644
--- a/tasks/nova_post_install.yml
+++ b/tasks/nova_post_install.yml
@@ -51,7 +51,9 @@
       dest: "/etc/nova/policy.json-{{ nova_venv_tag }}"
       config_overrides: "{{ nova_policy_overrides }}"
       config_type: "json"
-  notify: Restart nova services
+  notify:
+    - Manage LB
+    - Restart nova services
   tags:
     - nova-config
     - nova-post-install
@@ -64,7 +66,9 @@
     group: "root"
   with_fileglob:
     - rootwrap.d/*
-  notify: Restart nova services
+  notify:
+    - Manage LB
+    - Restart nova services
   tags:
     - nova-config
     - nova-post-install
diff --git a/tasks/nova_uwsgi.yml b/tasks/nova_uwsgi.yml
index e8aeefab..7400ddca 100644
--- a/tasks/nova_uwsgi.yml
+++ b/tasks/nova_uwsgi.yml
@@ -30,6 +30,7 @@
   with_items: "{{ filtered_nova_services }}"
   when: item.wsgi_app | default(False)
   notify:
+    - Manage LB
     - Restart nova services
 
 # Cleanup and restart nginx configuration