[tor-project] More resources required for Snowflake bridge

David Fifield david at bamsoftware.com
Tue Mar 1 23:26:48 UTC 2022

It has been great to see all the support and encouragement for people running Snowflake proxies. Thank you!

But there is a problem: the Snowflake bridge (which all the temporary proxies forward their traffic to) is going as fast as can on its current hardware. The server is running close to 100% on all CPUs more or less constantly. As more people use Snowflake, they each get a smaller share of the limited available performance. The limited capacity of the bridge is the cause of the [recent slowness of Snowflake](https://www.reddit.com/r/TOR/comments/t49i14)—in the past 2 weeks it's gone [from 12,000 to 16,000 users, without a proportional increase in bandwidth](https://metrics.torproject.org/rs.html#details/5481936581E23D2D178105D44DB6915AB06BFB7F).*

We've spent significant engineering resources already to make the most of the hardware, such as [load balancing multiple tor instances](https://github.com/net4people/bbs/issues/103) since a few weeks ago. This effort has roughly doubled the available bandwidth of the bridge, but it's still not enough. Demand will only continue to rise.

The bridge needs to be moved to faster hardware. Its current hosting is free of charge, but is already on the highest-spec VPS configuration (8 CPUs, 16 GB). Switching to a server with, say, double the CPUs will have an immediate positive effect: the proof of that is that while we were installing the load balancing on the main bridge, I paid for an only slightly higher-spec server to handle Snowflake traffic during the upgrade, and during that week the bandwidth [immediately rose to higher than where it is now](https://github.com/net4people/bbs/issues/103#issuecomment-1033067920). I used Snowflake a lot during that week, and the difference was palpable.

The minimum server required has something like 16 CPUs and 32 GB of RAM. meskio found some suitable [dedicated servers for about $200/month](https://lists.torproject.org/pipermail/anti-censorship-team/2022-February/000220.html) with unlimited bandwidth. (I estimate current needs are something like [100 TB/month of bandwidth](https://bugs.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/40095#note_2774428), of course expected to grow.)

I'm writing this to make people aware that the current cause of poor Snowflake performance is known: it's limited CPU capacity at the bridge, not general Tor slowness or slowness of the temporary proxies. Solving the problem will cost a few hundred dollars per month, at least for the near future. I am open to suggestions about what to do. I promised myself I would not again get in the situation of paying out of pocket for important infrastructure. I've already contacted the Open Technology Fund about a possible rapid response grant, but have not gotten a response yet. I'm willing to continue administering the bridge, as I do now.

* Since 2022-02-03, Tor Metrics graphs for the Snowflake bridge are 1/4 what they should be, until the fix for https://bugs.torproject.org/tpo/network-health/metrics/onionoo/40022 is deployed.

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