Improve deployment performance on large clusters

This change makes the host file prep and setup a lot faster
especially when deploying against very large clusters. The
change moves away from the lineinfile module and instead generates
a script with the same capabilities and then executes the script.
The generated script is stored in locally on the remote host
at "/usr/local/bin/openstack-host-hostfile-setup.sh" and can be
executed at any time to fix and or clean up host file problems.

Change-Id: Idca583deb403fce2b15a3dbc6255bb3bf92d9446
Signed-off-by: Kevin Carter <kevin.carter@rackspace.com>

tasks/openstack_update_hosts_file.yml

@@ -13,35 +13,15 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-- name: Update hosts file remove stale IP entries
-  lineinfile:
-    dest: /etc/hosts
-    regexp: "^{{ hostvars[item]['ansible_ssh_host'] }} (?!{{ item }}$)"
-    state: absent
-  with_items:
-    - "{{ groups['all_containers'] }}"
-    - "{{ groups['hosts'] }}"
+- name: Drop hosts file entries script
+  template:
+    src: "openstack-host-hostfile-setup.sh.j2"
+    dest: "/usr/local/bin/openstack-host-hostfile-setup.sh"
+    mode: "0755"
   tags:
     - openstack-host-hostfile
 
-- name: Update hosts file remove stale Host entries
-  lineinfile:
-    dest: /etc/hosts
-    regexp: "(?<!^{{ hostvars[item]['ansible_ssh_host'] }}) {{ item }}$"
-    state: absent
-  with_items:
-    - "{{ groups['all_containers'] }}"
-    - "{{ groups['hosts'] }}"
-  tags:
-    - openstack-host-hostfile
-
-- name: Update hosts file from ansible inventory
-  lineinfile:
-    dest: /etc/hosts
-    line: "{{ hostvars[item]['ansible_ssh_host'] }} {{ item }}"
-    state: present
-  with_items:
-    - "{{ groups['all_containers'] }}"
-    - "{{ groups['hosts'] }}"
+- name: Update hosts file
+  command: "/usr/local/bin/openstack-host-hostfile-setup.sh"
   tags:
     - openstack-host-hostfile

templates/openstack-host-hostfile-setup.sh.j2

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+# {{ ansible_managed }}
+
+set -x
+
+{% for item in groups['all'] %}
+sed -i '/^{{ hostvars[item]["ansible_ssh_host"] }}.*/d' /etc/hosts
+echo '{{ hostvars[item]["ansible_ssh_host"] }} {{ item }}' | tee -a /etc/hosts
+{% endfor %}