Reduction in Windows CI capacity

[Ben Gamari]

tl;dr. GHC's CI capacity will be a reduced due to a loss of sponsorship,
       particularly in Windows runner capacity. Help wanted in finding
       additional capacity.


Hi all,

For many years Google X has generously donated Google Compute Engine
resources to GHC's CI infrastructure. We all owe a debt of gratitude to
Google X for providing us with what has undoubtedly amounted to tens of
thousands of dollars of computational capacity over the years. I would
especially like to thank Greg Steuck, whose advocacy made this donation
possible.

Of course, organizational priorities understandably change and Google X
will be unable to continue their sponsorship in the future. This puts us
in a bit of a tricky situation; Google Compute Engine is currently the
home of nearly 100 cores worth of CI capacity, including:

  * roughly 20% of our x86-64/Linux capacity
  * our only x86-64/FreeBSD runner
  * all five of our x86-64 Windows runners

While the Linux runners are fairly easy to replace, the Windows capacity
is a bit harder since Windows cloud capacity is quite expensive (IIRC
nearly half of the cost of our Windows GCE instances is put towards the
license).

In the short term I can cover for some of this lost capacity by bringing
up a Windows runner using our generous donation from Packet [1].
However, I am extrmely wary of outspending our welcome on Packet's
infrastructure and therefore we will need to accept a small reduction in
capacity for a bit while we work out a more sustainable path forward. We
will have to see how things go but it may be necessary to disable the
Windows jobs on (non-Marge) merge request validation pipelines.

I am looking into various options for again reaching our previous
capacity, but this is an area where you might be able to help:

 * Familiarity with Windows licensing. Unfortunately the details of Windows
   licensing for virtualization purposes are a bit tricky. I suspect
   that the cheapest way forward is a single Windows Server license on a
   large machine but if you are familiar with Windows licensing in this
   setting, please do be in touch.

 * Providing Windows licenses. If you know of an organization
   that may be able to donate Windows licenses either in-kind or via
   financial support, please do be in touch.

 * Providing Windows cloud instances. If you know of an organization
   that may be able to donate Windows cloud instances, do holler.

As always, we welcome any hardware or cloud instance contributions. Do
be in touch if you may be in an position to help out.

Cheers,

- Ben


[1] https://www.packet.com/
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