Fixing haproxy-playbook fails when installing on multiple hosts

This bug is triggered when haproxy is deployed on multiple hosts
and external_lb_vip is different than the internal one.
As all host receive the same configuration, and are expected
to restart the haproxy service more than once
(once during role and once post_tasks), the playbook will fail,
because the restart of the service fails. The restart of the
service fails on some hosts because haproxy tries to
start/bind to an ip the host doesn't have (avoiding ip conflicts)

This allows haproxy to bind on non_local addresses by
addng a sysctl change in the playbook: net.ipv4.ip_nonlocal_bind = 1
The sysctl is changed for the containers/systems
when external_lb_vip is different than internal address and
the number of haproxy hosts is more than one thanks to a group_var.

Side-effect: other services are able to bind on non-local addresses
if the sysctl is changed.

This could be overriden by setting the variable haproxy_bind_on_non_local
in your user_* variables. If set to false, then the ip_non_local_bind
sysctl won't be changed.

Closes-Bug: #1487409

Change-Id: I41b3a5a4ba2d48192b505e3720456a77484aa92b

playbooks/inventory/group_vars/hosts.yml

@@ -226,3 +226,6 @@ swift_system_shell: /bin/bash
 swift_system_comment: swift system user
 swift_system_home_folder: "/var/lib/{{ swift_system_user_name }}"
 swift_service_region: "{{ service_region }}"
+
+## HAProxy
+haproxy_bind_on_non_local: "{% if groups.haproxy_hosts[1] is defined and internal_lb_vip_address != external_lb_vip_address %}True{% else %}False{% endif %}"

playbooks/roles/haproxy_server/defaults/main.yml

@@ -67,6 +67,7 @@ haproxy_backup_nodes: []
 #         - "httplog"
 
 galera_monitoring_user: monitoring
+haproxy_bind_on_non_local: False
 
 ## haproxy SSL
 haproxy_ssl: no

playbooks/roles/haproxy_server/tasks/haproxy_install.yml

@@ -24,7 +24,7 @@
   tags:
     - haproxy-apt-packages
 
-- name: Install HAPRoxy Packages
+- name: Install HAProxy Packages
   apt:
     pkg: "{{ item }}"
     state: latest

playbooks/roles/haproxy_server/tasks/haproxy_post_install.yml

@@ -13,6 +13,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+- name: Make haproxy bindable on non local addresses
+  sysctl:
+    name: net.ipv4.ip_nonlocal_bind
+    value: 1
+    sysctl_set: yes
+    state: present
+  when: haproxy_bind_on_non_local | bool
+
 - name: Drop base haproxy config
   template:
     src: "{{ item }}"