Reimplement external LB management handler hook

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

This reverts commit f876cf2926d5a80bd4e8b3acd6da2e9553b98e8f.

Change-Id: Ib17c9ae6f5e75ce2288d52f6368cd40e9586ffdb

defaults/main.yml

@@ -187,9 +187,6 @@ galera_ssl_address: "{{ ansible_host }}"
 # setting in the systemd unit file for MariaDB on CentOS 7 hosts.
 galera_disable_privatedevices: no
 
-# Allow the playbook to orchestrate service restart handlers
-galera_external_restart_handlers: no
-
 ## Set default mirror for openSUSE repositories
 # NOTE(hwoarang): Ensure that the full path to the 'opensuse' directory is used.
 #galera_server_opensuse_mirror_obs_url: "http://widehat.opensuse.org"

doc/source/index.rst

@@ -29,3 +29,16 @@ Example playbook
 
 .. literalinclude:: ../../examples/playbook.yml
    :language: yaml
+
+External Restart Hooks
+~~~~~~~~~~~~~~~~~~~~~~
+
+When the role performs a restart of the mariadb 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``, that way external roles
+can manage the load balancer endpoints responsible for sending traffic to the
+MariaDB 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.

handlers/main.yml

@@ -29,7 +29,6 @@
   when:
      - not galera_running_and_bootstrapped | bool
      - ansible_pkg_mgr != "zypper"
-     - not galera_external_restart_handlers | bool
   register: galera_restart
   until: galera_restart | success
   retries: 3
@@ -71,7 +70,6 @@
     - not galera_running_and_bootstrapped | bool
     - not galera_existing_cluster | bool and inventory_hostname == galera_server_bootstrap_node
     - ansible_pkg_mgr == "zypper"
-    - not galera_external_restart_handlers | bool
 
 - name: "Ensure node is not in bootstrap mode"
   lineinfile:
@@ -83,7 +81,6 @@
     - not galera_running_and_bootstrapped | bool
     - (not galera_existing_cluster | bool) or (not inventory_hostname == galera_server_bootstrap_node)
     - ansible_pkg_mgr == "zypper"
-    - not galera_external_restart_handlers | bool
 
 - name: Restart mysql on SUSE
   service:
@@ -92,7 +89,6 @@
   when:
     - not galera_running_and_bootstrapped | bool
     - ansible_pkg_mgr == "zypper"
-    - not galera_external_restart_handlers | bool
   register: galera_restart
   until: galera_restart | success
   retries: 3
@@ -103,3 +99,7 @@
   notify:
     - "Remove stale .sst"
   listen: "Restart all mysql"
+
+- meta: noop
+  listen: Manage LB
+  when: false

tasks/galera_install_yum.yml

@@ -125,6 +125,7 @@
     - ansible_pkg_mgr in ['yum', 'dnf']
     - systemd_mysql_service.stat.exists
   notify:
+    - Manage LB
     - Reload the systemd daemon
     - Restart mysql
   tags:

tasks/galera_post_install.yml

@@ -78,7 +78,9 @@
       dest: /etc/mysql/debian.cnf
       config_overrides: "{{ galera_debian_cnf_overrides }}"
       config_type: "ini"
-  notify: Restart all mysql
+  notify:
+    - Manage LB
+    - Restart all mysql
   tags:
     - galera-config
     - galera-client-user-config
@@ -103,6 +105,7 @@
     mode: "0644"
   when: ansible_pkg_mgr != 'zypper'
   notify:
+    - Manage LB
     - Restart all mysql
     - Reload the systemd daemon
   tags:
@@ -130,6 +133,7 @@
   when:
     - ansible_service_mgr == 'systemd'
   notify:
+    - Manage LB
     - Reload the systemd daemon
     - Restart all mysql
   tags: