Add discovery and build for multiple CPU architectures

This adds support for discovery of repo build servers for multiple
CPU architectures. When multiple architectures are detected among the
repo servers, this patch allows repo-install to assign and store a list
of 'master' build servers for each CPU architecture, then use this to
build artifacts independently for each CPU architecture in the deployment.

Partially-Implements: bp/multi-arch-repo

Change-Id: Ibfb77cc4ce87c9064f9af84946c5a9bbba5e1fb4

playbooks/repo-build.yml

@@ -13,14 +13,28 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+- name: Group repo servers by architecture
+  hosts: repo_all
+  tasks:
+    - name: Group repo servers by architecture
+      group_by:
+        key: repo_servers_{{ ansible_architecture }}
+      tags:
+        - "repo-build"
+
+# repo_all[0] is built last to ensure it has all build artifacts for final indexing
 - name: Build new repo packages for a given release
-  hosts: repo_all[0]
+  hosts: repo_all[1:],repo_all[0]
   gather_facts: true
   user: root
+  serial: 1
   pre_tasks:
     - name: Load local packages
       debug:
         msg: "Loading Packages"
+      when:
+        - "groups['repo_servers_{{ ansible_architecture }}'] | length > 0"
+        - "inventory_hostname == groups['repo_servers_{{ ansible_architecture }}'][0]"
       with_py_pkgs: "{{ pkg_locations }}"
       register: local_packages
       tags:
@@ -28,6 +42,9 @@
   roles:
     - role: "repo_build"
       repo_build_release_tag: "{{ openstack_release }}"
+      when:
+        - "groups['repo_servers_{{ ansible_architecture }}'] | length > 0"
+        - "inventory_hostname == groups['repo_servers_{{ ansible_architecture }}'][0]"
       tags:
         - "repo-build"
   vars:

releasenotes/notes/multi-arch-support-a8762f6ea7fdbcef.yaml

@@ -0,0 +1,8 @@
+---
+features:
+  - The repo install process is now able to support building and synchronizing
+    artifacts for multiple CPU architectures. To support multiple architectures,
+    one or more repo servers must be created for each CPU architecture in the
+    deployment. When multiple CPU architectures are detected among the repo
+    servers, the repo-discovery process will automatically assign a repo
+    master to perform the build process for each architecture.