[windows] Add environment variable RACKER_WDM_PROVIDER

This can be used to reconfigure the Vagrant virtualization backend
differently than VirtualBox.

Possible values are, in alphabetical order, `hyperv`, `virtualbox`,
`qemu`, `vmware_fusion`, `vmware_workstation`. It has been tested with
`virtualbox` only.

Author: amotl

CHANGES.rst

@@ -22,6 +22,9 @@ in progress
 - Rename environment variables used to control the Windows Docker Machine
   subsystem. The new names are ``RACKER_WDM_VCPUS``, ``RACKER_WDM_MEMORY``,
   and ``RACKER_WDM_MACHINE``.
+- Add environment variable ``RACKER_WDM_PROVIDER`` to reconfigure the
+  Vagrant virtualization backend differently than VirtualBox.
+
 
 2022-05-20 0.2.0
 ================

doc/winrunner.rst

@@ -79,8 +79,26 @@ reset the `Windows Docker Machine`_ installation directory. For example, it is:
 - On Linux: ``/root/.local/state/racker/windows-docker-machine``
 - On macOS: ``/Users/amo/Library/Application Support/racker/windows-docker-machine``
 
-Runtime
-=======
+
+VM provider
+===========
+
+`Vagrant`_ is able to use different providers as virtualization backend. By
+default, Racker selects `VirtualBox`_. In order to change the backend,
+reconfigure this environment variable::
+
+    export RACKER_WDM_PROVIDER=vmware_workstation
+
+Possible values are, in alphabetical order, ``hyperv``, ``virtualbox``,
+``qemu``, ``vmware_fusion``, ``vmware_workstation``.
+
+Please note that this has not been tested with providers other than
+`VirtualBox`_, so we would welcome to receive feedback from the community
+whether this also works well for them on other hypervisors.
+
+
+VM machine
+==========
 
 The architecture of Windows leads to container compatibility requirements that
 are different than on Linux, more background about this detail can be found at
@@ -444,6 +462,8 @@ The whole software catalog can be inquired at `Chocolatey community packages`_.
 .. _Overview of System Center release options: https://docs.microsoft.com/en-us/system-center/ltsc-and-sac-overview
 .. _Python: https://www.python.org/
 .. _Using Racker and Postroj for CrateDB CI: https://github.com/cicerops/racker/blob/main/doc/cratedb.rst
+.. _Vagrant: https://www.vagrantup.com/
+.. _VirtualBox: https://www.virtualbox.org/
 .. _Windows Container Base Images: https://docs.microsoft.com/en-us/virtualization/windowscontainers/manage-containers/container-base-images
 .. _Windows container version compatibility: https://docs.microsoft.com/en-us/virtualization/windowscontainers/deploy-containers/version-compatibility
 .. _Windows Docker Machine: https://github.com/StefanScherer/windows-docker-machine

postroj/winrunner.py

@@ -24,6 +24,7 @@
 
 class WinRunner:
 
+    VAGRANT_PROVIDER = os.environ.get("RACKER_WDM_PROVIDER", "virtualbox")
     VCPUS = os.environ.get("RACKER_WDM_VCPUS", 4)
     MEMORY = os.environ.get("RACKER_WDM_MEMORY", 4096)
 
@@ -129,7 +130,7 @@ def start(self, provision=False):
             provision_option = ""
             if provision:
                 provision_option = "--provision"
-            cmd(f"vagrant up --provider=virtualbox {provision_option} {self.wdm_machine}", cwd=self.wdmdir, use_stderr=True)
+            cmd(f"vagrant up --provider={self.VAGRANT_PROVIDER} {provision_option} {self.wdm_machine}", cwd=self.wdmdir, use_stderr=True)
 
         logger.info("Pinging Docker context")
         if not self.docker_context_online():