EU datacenters

[alex]

I've been playing around with an app hosted on EU datacenters for the
past few days and I've gotta say it's been a freaking awesome
experience so far, especially for what concerns latency.

It's been so great that I think we'll go live next month with this app.
There's one thing I'm not sure of: it's a TT program as far I as can
tell so, when there's an issue does one create it as usually on the
issue tracker, even if it's a production one?

For instance, there's something weird going on with the memcache
service right now, it shows all 0 and says "Could not retrieve
statistics. Try again shortly."

thanks.

[Marcel Manz]

I fully agree to the low latency and especially like the long living instances ;-)

Do you know by chance if the status page (http://code.google.com/status/appengine) is showing aggregated values for both US / EU hosted apps or will Google provide a separate status page for EU apps only? From what I've seen it's unlikely that EU hosted apps are affected the same way as US hosted apps as monitored on this status page.

Thanks
Marcel

[alex]

I don't really know but it feels like they're separated so I guess app
engine team folks will add links/combo box to the status page with
eu/us. but that'll probably happen when eu location will be generally
available, I suppose.

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[Igor Kharin]

Oh, lucky you! Does it feels, well, less crowded there? :)

And more importantly, what are latencies? Like, approximately, what's
the delta between "ping ghs.google.com" and "time wget http://$EUAPP"?
From what I see with edge-cached pages it might be around 30+ ms.

Thanks.

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[alex]

So, we're planning on going live/production with an app located in EU,
unless you guys think this is too early. I don't mind interruptions
here and there, it happends but, I'd like to avoid it as much as
possible :)

There's one thing that keeps bugging me: Memcache Viewer always shows
"Could not retrieve statistics. Try again shortly." (though memcache
service works just fine)

Should I create an issue on the public tracker or send it somewhere
else? I'd like to avoid posting app ID here, for now.

Thanks!

[alex]

Hey Igor,

I'm not sure what you mean: ping and wget really use different
protocols so it's probably not a fair comparison. Plus, AFAIK
ghs.google.com and ghs.googlehosted.com resolve to different IPs based
on your location (correct me if I'm wrong), so this too wouldn't be
fair. And another thing is, myapp.appspot.com is usually a CNAME to
ghs.google.com, googlehosted.com or similar (at least, in my setup),
so myapp.appspot.com and ghs.google.com is the same thing.

[Bay]

Cant wait for this to open to the rest of us!

[alex]

> myapp.appspot.com is usually a CNAME to
> ghs.google.com, googlehosted.com

sorry, what I meant is myapp.example.org CNAME ghs.google.com

[Igor Kharin]

Since what I care is latency, protocol overhead is insignificant in my case. It's odd, but is the best measure so far.

As ghs.* gets resolved to the nearest DC (which in my case is EU one) requests are "piped" throught it to App Engine servers. This EU-DC > US-DC > EU-DC thing is what makes apps slow to European users.

As an illustration:

$ ping ghs.google.com
PING ghs.l.google.com (173.194.71.121) 56(84) bytes of data.
64 bytes from lb-in-f121.1e100.net (173.194.71.121): icmp_req=1 ttl=44 time=90.2 ms
$ time wget http://$GAEAPP/
...
real 0m0.756s
user 0m0.008s
sys 0m0.004s
$ time wget http://$GAEAPP/
...
real 0m0.198s
user 0m0.000s
sys 0m0.004s

In last "wget" page got egde-cached (served from EU front-end) while 250-800+ ms is an "actual" latency to the app (paid, zero traffic, resident instance).

P.S: Have you tried to post your question on StackOverflow?

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[Igor Kharin]

And yeah, just before anybody got frightened by my latencies--I'm in
the middle of Siberia. It's about speed of light[1], actually. It's
not so fast.

[1] http://www.igvita.com/2012/07/19/latency-the-new-web-performance-bottleneck/

[Randy Shoup]

Hi, Alex --

  Thanks for the re-report.  We are looking into your Memcache Viewer issue now.  FWIW, it looks like the behavior is intermittent, so refreshing the Viewer can show the statistics.  That's not particularly satisfying, but it might get you a bit farther at the moment.

Thanks,

-- Randy

[alex]

Hey, Randy.

huh... true. that seems to do the trick, thanks!
I'm totally happy now :)

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[Sérgio Silva]

Any way to migrate an existing app to the EU datacenter or plans to add this ability in the future?

Regards,

Sérgio