[windows] Fix idempotence when reinstalling same pinned version

tasks/main.yml

@@ -22,15 +22,15 @@
   include_tasks: pkg-windows.yml
   when: ansible_os_family == "Windows"
 
-- name: Linux Install Tasks (Agent 5)
+- name: Linux Configuration Tasks (Agent 5)
   include_tasks: agent5-linux.yml
   when: datadog_agent_major_version|int == 5 and ansible_os_family != "Windows"
 
-- name: Linux Install Tasks
+- name: Linux Configuration Tasks
   include_tasks: agent-linux.yml
   when: datadog_agent_major_version|int > 5 and ansible_os_family != "Windows"
 
-- name: Agent6 Install Tasks (Windows)
+- name: Windows Configuration Tasks
   include_tasks: agent-win.yml
   when: datadog_agent_major_version|int > 5 and ansible_os_family == "Windows"
 

tasks/pkg-windows.yml

@@ -4,48 +4,81 @@
     msg: "The Datadog ansible role does not currently support Agent 5"
   when: datadog_agent_major_version|int == 5
 
+# This is a best-effort solution to avoid redownloading the msi when 
+# It won't work with rc / beta builds, and won't work if the version to install
+# is not pinned (as we don't know what version latest will be before downloading
+# the package).
+- name: Check currently installed Agent version
+  win_shell: |
+    $product_name = "Datadog Agent"
+    $query = "Select Name,IdentifyingNumber,InstallDate,InstallLocation,ProductID,Version FROM Win32_Product where Name like '$product_name%'"
+    $installs = Get-WmiObject -query $query
+
+    if (!$installs -or ($installs.Count -eq 0) -or ($installs.Count -gt 1)) {
+      Write-Host ""
+    } else {
+      $ddmaj, $ddmin, $ddpatch, $ddbuild = $installs.Version.split(".")
+      Write-Host "$($ddmaj).$($ddmin).$($ddpatch)"
+    }
+  register: version_check
+  changed_when: false # By default win_shell returns changed, but we know this script doesn't change anything.
+
+- name: Initialize skip install flag to false
+  set_fact:
+    datadog_skip_windows_install: "False"
+
+- name: Set skip install flag if version already installed
+  set_fact:
+    datadog_skip_windows_install: "{{ version_check.stdout | trim == datadog_agent_windows_version }}"
+  when: datadog_agent_windows_version is defined
+
 - name: Download windows datadog agent 614 fix script
   win_get_url:
     url: "{{ datadog_windows_614_fix_script_url }}"
     dest: '%TEMP%\fix_6_14.ps1'
+  when: not datadog_skip_windows_install
 
 - name: Run 6.14.0/1 PowerShell fix
   win_shell: |
     Set-ExecutionPolicy Bypass -Scope Process -Force
     &$env:temp\fix_6_14.ps1
+  when: not datadog_skip_windows_install
 
 - include_tasks: win_agent_latest.yml
-  when: datadog_agent_windows_version is not defined
+  when: (not datadog_skip_windows_install) and (datadog_agent_windows_version is not defined)
 
 - include_tasks: win_agent_version.yml
-  when: datadog_agent_windows_version is defined
+  when: (not datadog_skip_windows_install) and (datadog_agent_windows_version is defined)
 
 - name: show URL var
   debug:
     var: dd_download_url
+  when: not datadog_skip_windows_install
 
 - include_tasks: pkg-windows-opts.yml
+  when: not datadog_skip_windows_install
 
 - name: pre-Delete temporary msi
   win_file:
     path: '%TEMP%\ddagent.msi'
     state: absent
+  when: not datadog_skip_windows_install
 
 - name: Download windows datadog agent
   win_get_url:
     url: "{{ dd_download_url }}"
     dest: '%TEMP%\ddagent.msi'
   register: download_msi_result
-
+  when: not datadog_skip_windows_install
 
 - name: Install downloaded agent
   win_package:
     path: "{{ download_msi_result.dest }}"
     arguments: "{{ win_install_args }}"
-  when: not ansible_check_mode
+  when: (not datadog_skip_windows_install) and (not ansible_check_mode)
 
 - name: Delete temporary msi
   win_file:
     path: "{{ download_msi_result.dest }}"
     state: absent
-  when: download_msi_result.status_code == 200
+  when: (not datadog_skip_windows_install) and (download_msi_result.status_code == 200)