Allow a venv to be downloaded from a URL

In order to enable the ability to build venvs on a target,
then serve them via http(s) from a central storage host,
we enable the ability to set the path to be a URL. If this
is done then the venvs will be sourced from that URL when
installing.

Change-Id: I166de361f568bfdf28c0f5d916ff8175827c45f4

defaults/main.yml

@@ -70,10 +70,13 @@ venv_reuse_build_only: no
 # venvs.
 venv_reuse_build_wheels: yes
 
-# The path where a built venv should be stored on the
-# deployment host. By default, ensure that the location
-# separates venvs per distribution and architecture to
-# prevent re-use of venvs between them.
+# The path where a built venv is stored on the By default,
+# a path on the deployment host is used which ensures that
+# the location separates venvs per distribution and architecture
+# to prevent re-use of venvs between them. If the path set
+# begins with http(s):// then the install process will
+# recognise this and deploy from a URL instead of the
+# deployment host.
 venv_reuse_download_venv_path: "{{ lookup('env', 'HOME') | default('/opt', true) }}/cache/venvs/{{ venv_reuse_download_subfolder }}"
 
 # NOTE(hwoarang): ansible_distribution may return a string with spaces
@@ -81,7 +84,8 @@ venv_reuse_download_venv_path: "{{ lookup('env', 'HOME') | default('/opt', true)
 # in order to create a more sensible repo name for the distro.
 venv_reuse_download_subfolder: "{{ (ansible_distribution | lower) | replace(' ', '_') }}-{{ ansible_distribution_version.split('.')[:2] | join('.') }}-{{ ansible_architecture | lower }}"
 
-# The owner of the venv_reuse_download_venv_path
+# The owner of the venv_reuse_download_venv_path if it is
+# housed on the deployment host.
 venv_reuse_download_path_owner: "{{ lookup('env', 'USER') | default('root', true) }}"
 
 # The path where the wheels are cached on the target host

tasks/python_venv_build.yml

@@ -79,7 +79,8 @@
     - venv changed
 
 - name: Package the venv when venv_reuse_enable is enabled
-  when: venv_reuse_enable | bool
+  when:
+    - venv_reuse_enable | bool
   block:
 
   - name: Clean up the virtualenv before packaging
@@ -124,5 +125,6 @@
       - src: "{{ venv_destination_path }}.checksum"
         dest: "{{ venv_reuse_download_venv_path }}/{{ venv_destination_path | basename }}.checksum"
     when:
+      - _venv_source == 'file'
       - _venv_package_build is mapping
       - _venv_package_build | changed

tasks/python_venv_install.yml

@@ -18,14 +18,33 @@
     src: "{{ venv_reuse_download_venv_path }}/{{ venv_destination_path | basename }}.checksum"
     dest: "{{ venv_destination_path | dirname }}/"
   register: _venv_checksum_copy
+  when:
+    - _venv_source == 'file'
+
+- name: Retrieve checksum for venv download
+  uri:
+    url: "{{ venv_reuse_download_venv_path }}/{{ venv_destination_path | basename }}.checksum"
+    dest: "{{ venv_destination_path | dirname }}/"
+    return_content: yes
+  register: _venv_checksum_download
+  when:
+    - _venv_source == 'url'
+
+- name: Attempt venv download
+  get_url:
+    url: "{{ venv_reuse_download_venv_path }}/{{ venv_destination_path | basename }}.tgz"
+    dest: "{{ venv_destination_path | dirname }}/"
+    checksum: "sha1:{{ _venv_checksum_download.content | trim }}"
+  when:
+    - _venv_source == 'url'
 
 - name: Remove existing venv on target host if it is changing
   file:
     path: "{{ venv_destination_path }}"
     state: absent
   when:
-    - _venv_checksum_copy is mapping
-    - _venv_checksum_copy | changed
+    - (_venv_checksum_copy is mapping and _venv_checksum_copy | changed) or
+      (_venv_checksum_download is mapping and _venv_checksum_download | changed)
 
 - name: Create venv directory on the target host
   file:
@@ -40,6 +59,7 @@
     remote_src: no
   when:
     - (_venv_checksum_copy is mapping and _venv_checksum_copy | changed) or
+      (_venv_checksum_download is mapping and _venv_checksum_download | changed) or
       _venv_dir_create | changed
   notify:
     - venv changed
@@ -53,6 +73,7 @@
     warn: no
   when:
     - (_venv_checksum_copy is mapping and _venv_checksum_copy | changed) or
+      (_venv_checksum_download is mapping and _venv_checksum_download | changed) or
       _venv_dir_create | changed
   tags:
     - skip_ansible_lint

tasks/python_venv_preflight.yml

@@ -32,6 +32,10 @@
     - venv_reuse_build_only | bool
     - not venv_reuse_enable | bool
 
+- name: Check whether the venv_reuse_download_venv_path is a URL or a file path
+  set_fact:
+    _venv_source: "{{ (venv_reuse_download_venv_path is match('^https?://.*')) | ternary('url', 'file') }}"
+
 - name: Ensure that venv_reuse_download_path exists on the deployment host
   file:
     path: "{{ venv_reuse_download_venv_path }}"
@@ -40,6 +44,7 @@
   delegate_to: localhost
   run_once: yes
   when:
+    - _venv_source == 'file'
     - venv_reuse_enable | bool
 
 - name: Check if venv tgz is present on the deployment host
@@ -53,6 +58,7 @@
   delegate_to: localhost
   run_once: yes
   when:
+    - _venv_source == 'file'
     - venv_reuse_enable | bool
 
 - name: Ensure that virtualenv is installed on the destination host

tasks/python_venv_set_facts.yml

@@ -29,6 +29,9 @@
     - (_venv_checksum_copy is defined and
        _venv_checksum_copy is mapping and
        _venv_checksum_copy | changed) or
+      (_venv_checksum_download is defined and
+       _venv_checksum_download is mapping and
+       _venv_checksum_download | changed) or
       (_install_venv_pip_packages is defined and
        _install_venv_pip_packages is mapping and
        _install_venv_pip_packages | changed)