Comment 6 for bug 2034656

pro-client doesn't run apt upgrade in any scenario or configure the system to do so.

Do we have control over any of the offending machines? I'd still like to see a `pro collect-logs` from one of them to be sure nothing unexpected is happening pro-client related.

That the major offending package is azure-specific may be a clue that it could be something happening only on Azure. We can talk to the cloud team about it. We would only see the spike on esm.ubuntu.com because clouds use mirrors for the main archive. Adding cloud-images here which I think will notify them.

I went ahead and checked default apt configuration on a couple machines and found the following:
on Azure Bionic Pro:
$ apt-config dump | grep Periodic
APT::Periodic "";
APT::Periodic::Update-Package-Lists "1";
APT::Periodic::Download-Upgradeable-Packages "0";
APT::Periodic::AutocleanInterval "0";
APT::Periodic::Unattended-Upgrade "1";

on GCP Bionic Pro:
$ apt-config dump | grep Periodic
APT::Periodic "";
APT::Periodic::Update-Package-Lists "1";
APT::Periodic::Download-Upgradeable-Packages "0";
APT::Periodic::AutocleanInterval "1";
APT::Periodic::Unattended-Upgrade "1";

So at least in those two places, "Download-Upgradeable-Packages" is disabled ("0"), which I believe is what corresponds to the apt upgrade --download-only in apt.daily, but I'm out of my depth here. Just to be sure though, I'm also adding this bug to apt in case this is a problem with default configuration there.