[judofyr]

> What do you mean by this part? tailetc is a library used by the client of etcd.

Oh. Since they have a full cache of the database I thought it was intended to be used as a separate set of servers layered in front of etcd to lessen the read load. But you're actually using it directly? Interesting. What's the impact on memory usage and scalability? Are you not worried that this will not scale over time since all clients need to have all the data?

[bradfitz]

Well, we have exactly 1 client (our 1 control server process).

So architecturally it's:

3 or 5 etcd (forget what we last deployed) <--> 1 control process <--> every Tailscale client in the world

The "Future" section is about bumping "1 control process" to "N control processes" where N will be like 2 or max 5 perhaps.

The memory overhead isn't bad, as the "database" isn't big. Modern computers have tons of RAM.

[judofyr]

You're able to serve all your clients from a single control process? And this would probably work for quite a while? Then I struggle to see why you couldn't just use SQLite. On startup read the full database into memory. Serve reads straight from memory. Writes go to SQLite first and if it succeeds then you update the data in memory. What am I missing here?

[crawshaw]

We could use SQLite. (I love SQLite and have written about it before!) The goal is N control processes not for scale, but for more flexibility with deployment, canarying, etc.

[judofyr]

That makes sense. Thanks for answering all of my critical questions. Looks like a very nice piece of technology you’re building!

[robmccoll]

I'm curious what drove the decision to move to an external store (and multinode HA config at that) now compared to using a local Go KV store like Badger or Pebble?

Given that the goals seem to be improving performance over serializing a set of maps to disk as JSON on every change and keeping complexity down for fast and simple testing, a KV library would seem to accomplish both with less effort, without introducing dependence on an external service, and would enable the DB to grow out of memory if needed. Do you envision going to 2+ control processes that soon?

Any consideration given to running the KV store inside the control processes themselves (either by embedding something like an etcd or by integrating a raft library and a KV store to reinvent that wheel) since you are replicating the entire DB into the client anyway?

Meanwhile I'm working with application-sharded PG clusters with in-client caches with coherence maintained through Redis pubsub, so who am I to question the complexity of this setup haha.

[bradfitz]

Yes, we're going to be moving to 2+ control servers for HA + blue/green reasons pretty soon here.