Use updated get_url module checksum functionality

Starting in Ansible 2.0, the get_url [1] module provides the
ability for a checksum to be provided to the get_url module
which will be verified against the local destination file
and the task skipped if it matches.

[1] http://docs.ansible.com/ansible/get_url_module.html

This patch implements the use of this functionality.

The ability to ignore a venv download failure is also removed
as this is not necessary or desirable. It is better for the
download to fail and the playbook execution to stop immediately
so that the failure point is exposed.

Change-Id: I96e815e15d697ca738b0a7d4dd21b71bde9b68ce

meta/main.yml

@@ -4,7 +4,7 @@ galaxy_info:
   description: An Ansible Galaxy Role for Deploying OpenStack Gnocchi
   company:
   license: Apache
-  min_ansible_version: 1.9
+  min_ansible_version: 2.0
   platforms:
   - name: Ubuntu
     versions:

tasks/gnocchi_install.yml

@@ -39,47 +39,15 @@
   retries: 5
   delay: 2
 
-- name: Get local venv checksum
-  stat:
-    path: "/var/cache/{{ gnocchi_venv_download_url | basename }}"
-    get_md5: False
-  when:
-    - not gnocchi_identity_only | bool
-    - not gnocchi_developer_mode | bool
-  register: local_venv_stat
-
-- name: Get remote venv checksum
-  uri:
-    url: "{{ gnocchi_venv_download_url | replace('tgz', 'checksum') }}"
-    return_content: True
-  when:
-    - not gnocchi_identity_only | bool
-    - not gnocchi_developer_mode | bool
-  register: remote_venv_checksum
-
-# TODO: When project moves to ansible 2 we can pass this a sha256sum which will:
-#       a) allow us to remove force: yes
-#       b) allow the module to calculate the checksum of dest file which would
-#          result in file being downloaded only if provided and dest sha256sum
-#          checksums differ
 - name: Attempt venv download
   get_url:
     url: "{{ gnocchi_venv_download_url }}"
     dest: "/var/cache/{{ gnocchi_venv_download_url | basename }}"
-    force: yes
-  failed_when: false
-  register: get_venv
+    checksum: "sha1:{{ lookup('url', gnocchi_venv_download_url | replace('tgz', 'checksum')) }}"
+  register: gnocchi_get_venv
   when:
     - not gnocchi_identity_only | bool
     - not gnocchi_developer_mode | bool
-    - (local_venv_stat.stat.exists == False or
-        {{ local_venv_stat.stat.checksum is defined and local_venv_stat.stat.checksum != remote_venv_checksum.content | trim }})
-
-- name: Set gnocchi get_venv fact
-  set_fact:
-    gnocchi_get_venv: "{{ get_venv }}"
-  when:
-    - not gnocchi_identity_only | bool
 
 - name: Remove existing venv
   file:
@@ -126,7 +94,7 @@
   delay: 2
   when:
     - not gnocchi_identity_only | bool
-    - gnocchi_get_venv | failed or gnocchi_developer_mode | bool
+    - gnocchi_developer_mode | bool
   notify:
     - Restart Gnocchi services
     - Restart Apache
@@ -137,4 +105,4 @@
   when:
     - not gnocchi_identity_only | bool
     - not gnocchi_developer_mode | bool
-    - gnocchi_get_venv | success
+    - gnocchi_get_venv | changed or gnocchi_venv_dir | changed