Reminder: This maintenance is starting in about an
hour.
On 6/2/20 8:01 AM, Andrew Bogott wrote:
Hello!
Next week we'll be rebuilding and upgrading the hardware that
provides DNS service to cloud-vps and toolforge. These rebuilds will
start at 14:00 UTC and the whole process may take 2-3 hours. It's
likely that DNS lookups will be somewhat slower as clients fail over
between the in-progress and the working server. In theory there
should be few other user-facing effects from these upgrades.
In practice, though, this isn't something that we've done for quite a
while, and touching DNS is always risky since it underlies pretty
much everything. Here are some things to be ready for:
- As a precaution we'll be disabling Horizon during the window to
prevent new VMs or DNS changes landing in an inconsistent state.
- Some badly-behaved DNS clients won't fail over properly and will
report errors when their primary DNS server is down.
- Puppet will almost certainly experience transient failures, since
Puppet is known to be one of those badly-behaved clients.
- If things go very badly there may be periods of total DNS outage
which will result in many WMCS-hosted services failing. There's no
particular reason that this /should/ happen, but this is the
worst-case scenario.
For additional context, the phabricator task for this work is
https://phabricator.wikimedia.org/T253780
- Andrew + the WMCS team