[anti-censorship-team] Need to increase number of tor instances on snowflake-01 bridge, increased usage since yesterday

[Cecylia Bocovich]

On 2022-09-27 09:49, David Fifield wrote:
> On Fri, Sep 23, 2022 at 11:01:37AM -0400, Cecylia Bocovich wrote:
>> On 2022-09-22 11:24, David Fifield wrote:
>>> There is increased usage of the snowflake-01 bridge since yesterday,
>>> likely related to protests/shutdowns in Iran. The 4 load-balanced tor
>>> instances, which recently were at about 60% CPU at the steady state, are
>>> currently near 100%.
>>>
>>> I am planning to increase the number of instances today.
>> It looks like we're also reaching proxy capacity again for the first time in
>> a while.
>>
>> I've attached a visualization of available proxies that are compatible with
>> all types of client NATs. You can see in the first image that the number of
>> idle proxies has gone to zero and all available proxies are being matched.
>> The second image shows spikes in the number of clients denied a working
>> proxy.
>>
>> The depletion of this proxy pool could be due to the high amount of mobile
>> network usage, since these networks are likely to have complex and
>> restrictive NAT topologies.
> Besides recruiting more proxies, could we stretch the existing
> unrestricted proxies further? When a proxy finds its own NAT type to be
> unrestricted, it could increase its polling frequency and/or concurrent
> capacity.

That's a good idea.

I've started working on tackling the problem from the other side[0]: we 
have a lot of clients who may not need unrestricted proxies pulling from 
that pool because their NAT type is unknown (see attached image).

If we have these clients optimistically pull from the other pool, we 
could reduce the load substantially. However, this change will take a 
while to roll out because it has to be included in a Tor Browser release.

Updating proxies to poll more frequently is easier to roll out quickly.

[0] 
https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/-/issues/40178