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Re: Planning for a mirror using Google Cloud CDN

Hi Zach

On Mon, Nov 28, 2016 at 01:04:13PM -0800, Zach Marano wrote:
> The only question I have is if the regions are synced on different
> schedules will VM's in different regions get different repo data-
> irregardless of failover issues. In other words, will a user who has a VM
> in us-central1-a and asia-east1-c get different packages over the course of
> a day.

If we use two-stage sync only within one regions, different regions may
finish updating at different times.  The exact difference depends on the
network speed, but I assume the would be at most 15 minutes apart.

With two-stage sync throughout the whole network we can get down to
maybe one minute.  Not much below, as we may want to be able to cache
them at least a little while in the CDN.

>        If so, that could break some users who may expect all of their
> instances to be in the same relative state. For example if you are using a
> config management solution and you expect after a config run that all of
> your instances have some version of package.

This can even happen now.  The updates of multiple machines are not
perfectly synchroniced and may see different versions of the archive
state (the Release file).  If you are just unlucky enough to hit the
mirror just as the sync goes the finishing touches, you'll see this
different states.  And as more machines you have, the larger is the


Those who hate and fight must stop themselves -- otherwise it is not stopped.
		-- Spock, "Day of the Dove", stardate unknown

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