RethinkDNS Resolver That Deploys to CF Workers, Deno Deploy, Fastly, Fly.io

https://github.com/serverless-dns/serverless-dns

by indigodaddy • 1 year ago

106 20 1 year ago

github.com

chrisweekly2• 1 year ago

Cool! "Pi-hole -esque" is a nice descriptor.

Tangent: Bunny.net is my new favorite CDN / cloud service provider. They have scriptable DNS too.

Imustaskforhelp• 1 year ago

Bunny requires a credit card for its free trial and it seems that it would only give 7 days free trial which is really weird.

So I am off to cloudflare workers free tier.

chrisweekly2• 1 year ago

FWIW Bunny added free credits (totaling $50) so my free trial is effectively MUCH longer than 7d. They're the fastest CDN, have awesome / intuitive UX, and very robust featureset.

Onavo• 1 year ago

The Rethink DNS mobile app hasn't seen a release in years. Is the project still alive?

https://github.com/celzero/rethink-app

ementally• 1 year ago

in years.

not even past 1 year.

See https://github.com/celzero/rethink-app/discussions/1884

withinboredom• 1 year ago

the development happens on the lead developer's feature branch

Oof. This makes me cringe so hard. I once took over a project (but the developer didn't know they were getting fired) and the guy was doing everything on his laptop, from his laptop. Deployments and builds were from his laptop. Even dependencies weren't checked into the code (using global installs of them on unknown versions). The owner had me come in because after talking to several people realized he was in a bad place.

It took me ~2 months to learn everything and document all the things. Then the owner fired him. That guy kept development back for so long by simply not documenting/sharing code and configuration. Now there's an entire team with a healthy development flow. But wow, I had some flashbacks reading that...

maxloh3• 1 year ago

I doubt their choice of implementing something so performance-critical as a DNS server in JavaScript. It seems like a slow language for that purpose.

When I was looking for ad-block solutions on Android, Rethink DNS was actually on the top of my list. However, when I found out that their server was written in JavaScript, I did some benchmarking.

Rethink's server processed DNS requests in 400-500ms, which could potentially make a new webpage render up to half a second slower the first time:

  ~ > curl -w "DNS Time: %{time_namelookup}s\nConnect: %{time_connect}s\nTotal: %{time_total}s\n" -H "accept: application/dns-message" -H "content-type: application/dns-message" --data "<binary-data>" -o nul -s https://sky.rethinkdns.com/1:6AcDACIBLIDAAFQwIAAACA==
  DNS Time: 0.004995s
  Connect: 0.142332s
  Total: 0.462496s

While the Cloudflare's server took just 5-10ms, as seen below:

  ~ > curl -w "DNS Time: %{time_namelookup}s\nConnect: %{time_connect}s\nTotal: %{time_total}s\n" -H "accept: application/dns-message" -H "content-type: application/dns-message" --data "<binary-data>" -o nul -s 1.1.1.1
  DNS Time: 0.000026s
  Connect: 0.006273s
  Total: 0.008822s

In the end, I chose AdAway and have stuck to that choice.

ignoramous5• 1 year ago

Rethink's server processed DNS requests in 40-60ms, which could potentially make a new webpage render up to 50ms slower the first time, while the system default took just 5-10ms

You can choose "system default" in the Rethink Android app from Configure -> DNS -> System DNS. You don't have to use Rethink's DoH (DNS over HTTPS) / DoT (DNS over TLS) servers. You can setup any DNSCrypt, Oblivious DoH, or plain old DNS endpoint with Rethink to forward DNS requests to.

I chose AdAway and have stuck to that choice for now

A decent choice.

A word of caution when using it in non-root mode, though: AdAway borrows code from another (now discontinued but pretty solid) project viz. DNS66. From when I looked at the code, DNS66 never handled DNS over TCP. You can test this with Termux: dig +tcp example.com A.

doubt their choice of implementing something so performance-critical as a DNS server in JavaScript

For a remotely-hosted DNS resolver, network latency & concurrency is likely to dominate than performance of the code itself. You're right that JS is slow (as compared to Rust, say), but looking at metrics from serving 300m to 3bn queries/day on Cloudflare, our median (CPU time) spent processing a DNS request was consistently less than 2ms, and IO wait (there are no "disks" so, this is mostly hitting the caches or upstream resolvers) was estimated to be less than 7ms.

Also, we employ a bunch of optimizations on client & the server, as appropriate (if we're missing any we should implement, let us know).

- Coalesce multiple requests into one upstream request: For example, if there's 40 clients all wanting to resolve the same domain (say, ipv4only.arpa) within milliseconds of each other, only one request is upstreamed.

- Utilize in-process LFU cache and Cloudflare's Cache API to avoid upstreaming where possible.

- Connection pool egress to avoid reconnect overheads.

- Race response for a query from multiple upstreams in parallel.

- Support TLS session resumption.

- Prefer the lighter TLS_AES_128_GCM_SHA256 cipher suite.

- Dynamically adjust the TLS frame size. DNS queries aren't that big.

- Disable Nagling on TCP.

- Rehydrate responses for top domains stored in the in-process cache in the background.

- Admission Control (load shedding) & queuing disciplines (CoDel etc)

---

curl -w "DNS Time: %{time_namelookup}s\nConnect: %{time_connect}s\nTotal: %{time_total}s\n" -H "accept: application/dns-message" -H "content-type: application/dns-message" --data "<binary-data>" -o nul -s 1.1.1.1

Shouldn't the switch "-s" be "https://one.one.one.one/dns-query"? For DoH perf specifically, I use https://github.com/ameshkov/godnsbench as it supports parallel and cache-busting (random) queries.

Ex:

Rethink on Workers:

  ./godnsbench -a https://sky.rethinkdns.com/dns-query -p 10 -c 300 -t 1 -q {random}.dnsleaktest.com
  godnsbench with the following configuration:
  {
    "Address": "https://sky.rethinkdns.com/dns-query",
    "Connections": 10,
    "Timeout": 1,
    "QueriesCount": 300,
  }

  The test results are:
  Elapsed: 6.120078941s
  Average QPS: 49.018394
  Processed queries: 300
  Average per query: 20.400765ms
  Errors count: 0

Cloudflare 1.1.1.1:

  ./godnsbench -a https://cloudflare-dns.com/dns-query -p 10 -c 300 -t 1 -q {random}.dnsleaktest.com
  godnsbench with the following configuration:
  {
    "Address": "https://cloudflare-dns.com/dns-query",
    "Connections": 10,
    "Timeout": 1,
    "QueriesCount": 300,
  }

  The test results are:
  Elapsed: 6.780474724s
  Average QPS: 44.244383
  Processed queries: 299
  Average per query: 22.677588ms
  Errors count: 1

maxloh3• 1 year ago

I was able to reproduce your results with the provided command. In that case, Rethink DNS is 1-2 ms faster than Cloudflare DNS. However, the provided command actually runs 300 queries in a really short timeframe (specified by -c 300), which is very different from real-world use cases — in most cases, we look up a domain only once, and the result is cached by the OS.

If we set the count parameter to 1 (closer to the mentioned real-world use cases), we can reproduce the result in my comment above. Rethink DNS actually takes 450 ms to return a response.

  ./godnsbench -c 1 -q google.com -a https://sky.rethinkdns.com/dns-query
  ...
  2025/05/04 23:22:47 [info] Average per query: 452.3948ms

With Cloudflare DNS, it takes only 35 ms, even when using DNS over HTTPS.

  ./godnsbench -c 1 -q google.com -a https://cloudflare-dns.com/dns-query
  ...
  2025/05/04 23:22:49 [info] Average per query: 34.4343ms

As sky.rethinkdns.com is hosted on Cloudflare, there shouldn't be any notable network differences between Rethink DNS and Cloudflare DNS. If you inspect the list of servers in the following two lists, they are almost identical.

- https://check-host.net/check-ping?host=https://sky.rethinkdn...

- https://check-host.net/check-ping?host=https://cloudflare-dn...

If CPU time isn't the bottleneck of response time, any idea what the reason is behind the difference in response time?

pjmlp2• 1 year ago

Indeed, then someone rewrites it in a compiled language and we get yet another "40x improvement" blog post.

ignoramous5• 1 year ago

40x improvement

Could WASM AoT bring about those? ;)

rewrites ... compiled language

With stuff like AutoFDO on Android, we've come a full circle with folks "JITing" compiled blocks... https://lwn.net/Articles/995397/

karel-3d• 1 year ago

Just fyi (not talking down this project, more providing alternatives) - dnsdist (part of OpenDNS "suite") which is mostly "sold" as a DNS load balancer - is also a perfect stub resolver, that can do DoH/DoT on both ends, that can block certain websites, and is very easy on resources.

Not that many people talk about its usage as a stub resolver, and I don't know why!

RethinkDNS Resolver That Deploys to CF Workers, Deno Deploy, Fastly, Fly.io

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