[tor-dev] Summary of meek's costs, October 2014

Tue Nov 4 17:47:10 UTC 2014

Here's the summary of meek's CDN fees for October 2014. Earlier reports:
https://lists.torproject.org/pipermail/tor-dev/2014-August/007429.html
https://lists.torproject.org/pipermail/tor-dev/2014-October/007576.html

           App Engine +  Amazon + Azure = total by month
February 2014   $0.09 +      -- +    -- =   $0.09
March 2014      $0.00 +      -- +    -- =   $0.00
April 2014      $0.73 +      -- +    -- =   $0.73
May 2014        $0.69 +      -- +    -- =   $0.69
June 2014       $0.65 +      -- +    -- =   $0.65
July 2014       $0.56 +   $0.00 +    -- =   $0.56
August 2014     $1.56 +   $3.10 +    -- =   $4.66
September 2014  $4.02 +   $4.59 + $0.00 =   $8.61
October 2014   $40.85 + $130.29 + $0.00 = $171.14
--
total by CDN   $49.15 + $137.98 + $0.00 = $187.13 grand total

Golly! I'm as shocked as you are. There was an explosion in users after
the release of Tor Browser 4.0 on October 15 (first attached image):
https://metrics.torproject.org/users.html?graph=userstats-bridge-transport&start=2014-08-01&end=2014-10-31&transport=meek#userstats-bridge-transport
Before that, we were mostly under the free thresholds on each service.
Now we're consistently exceeding those thresholds and getting charged at
the normal rate. For example, Amazon gives us 50 GB free each month;
last month we only used about 32 GB but this month it was about 480 GB.

There was really only half a month of heavy use, so next month I expect
the charges to be at least double. But I'm going to try to apply some
free credits; see below. At the moment, the most cost-effective backend
is meek-azure, because it's running on a free research grant for a year.

obfs3 is currently the most-used transport, with about 8000 simultaneous
users, compared to meek's 500.
https://metrics.torproject.org/users.html?graph=userstats-bridge-transport&start=2014-10-01&end=2014-10-31&transport=obfs3&transport=meek#userstats-bridge-transport
Just looking at the time period from October 15 to October 31, the mean
value of the obfs3 graph is 8075, and that of the meek graph is 450, a
ratio of 18:1. About 94% of October's meek users appeared after October
15. So a rough calculation of meek's monthly cost, if it were to become
as used as obfs3 is today, is
        $171.14 * 0.94 * (8075/450) * 3/2 ≈ $4300
The 3/2 comes from assuming that Azure will cost as much as the other
two eventually. The other big assumption in this calculation is that
costs scale linearly with users, which isn't quite true because of the
free thresholds and because of regional pricing differences.

== App Engine a.k.a. meek-google ==

This is the first month we had charges for "instance hours"; previously
we paid only for bandwidth. App Engine by default runs just one copy of
your app, but spins up new instances of it during increased load. You
get 28 instance hours for free each day, so as long as there's just one
instance you don't pay anything. The total cost of $40.85 broke down as
follows:
	289 GB             $34.72
	123 instance hours $6.13
The attached meek-google-costs-2014-11-01.png shows the breakdown of
costs between bandwidth and instance hours for the last few months.

On October 25 I experimented with upgrading the App Engine instance
class from "F1" to "F2".
https://cloud.google.com/appengine/docs/adminconsole/performancesettings#Setting_the_Frontend_Instance_Class
F2 has more CPU and I thought it might speed up TLS. F2 uses up instance
hours at twice the rate of F1, so even if you only have one instance you
pay for 20 hours. I downgraded the class back to F1 on October 27 when,
for the first time, we hit the daily spending limit of $5.00 I had set,
about 22 hours into the day. (I happened to be using meek-google at the
time, so I noticed right away when it stopped working.) I bumped back up
to F2 and increased the daily spending limit on October 31.

This month I'm going to try to activate a credit I have for App Engine,
which is $500 for three months. We'll probably run out of the $500
before the three months are up, because we're currently pretty close to
the $5 per day that implies.

The attached meek-google-2014-11-01.png shows B/s for the month.

== Amazon a.k.a. meek-amazon ==

The Amazon bill of $130.29 breaks down in a complicated way by region.
Each region has different free thresholds and different per-unit rates.
I've summarized it here but the actual bill has 31 line items. This
month is the first month with bandwidth charges; previously we had only
paid for the number of HTTPS requests.

Asia Pacific (Singapore)	  23M requests	$27.86	169 GB	$19.49
Asia Pacific (Sydney)		 150K requests	 $0.00	  1 GB	 $0.15
Asia Pacific (Tokyo)		  16M requests	$18.93	108 GB	$18.28
EU (Ireland)			  15M requests	$16.22	108 GB	$11.75
South America (Sao Paulo)	 180K requests	 $0.00	  1 GB	 $0.03
US East (Northern Virginia)	   8M requests	 $7.77	 92 GB	 $9.81

The attached meek-amazon-2014-11-01.png shows GB/day for the month.

== Azure a.k.a. meek-azure ==

Azure is still on a free grant for a year. Unfortunately I don't see a
way to find out what it would be costing or even get a report of monthly
bandwidth usage.

The attached meek-azure-2014-11-01.png shows GB/hour for the last seven
days of the month.

David Fifield
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