feat(users/flokli/nixos/nixos-tvix-cache): init r/8949

This is a fetch-through mirror of cache.nixos.org, hosted by NumTide.

The current machine is a SX65 Hetzner dedicated server with 4x22TB SATA disks,
and 2x1TB NVMe disks.

The goals of this machine:

 - Exercise tvix-store and nar-bridge code
 - Collect usage metrics (see https://nixos.tvix.store/grafana)
 - Identify bottlenecks
 - Replace cache.nixos.org?

Be however aware that there's zero availability guarantees. Since Tvix doesn't
support garbage collection yet, we either will delete data or order a bigger
box.

Change-Id: Id24baa18cae1629a06caaa059c0c75d4a01659d5
Reviewed-on: https://cl.tvl.fyi/c/depot/+/12811
Tested-by: BuildkiteCI
Reviewed-by: Jonas Chevalier <zimbatm@zimbatm.com>
Reviewed-by: flokli <flokli@flokli.de>

1 files changed, 40 insertions, 0 deletions

diff --git a/users/flokli/nixos/nixos-tvix-cache/README.md b/users/flokli/nixos/nixos-tvix-cache/README.md
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@@ -0,0 +1,40 @@
+# nixos-tvix-cache
+
+This is a fetch-through mirror of cache.nixos.org, hosted by NumTide.
+
+The current machine is a SX65 Hetzner dedicated server with 4x22TB SATA disks,
+and 2x1TB NVMe disks.
+
+The goals of this machine:
+
+ - Exercise tvix-store and nar-bridge code
+ - Collect usage metrics (see [Grafana](https://nixos.tvix.store/grafana))
+ - Identify bottlenecks in the current implementations and fix them
+ - Replace cache.nixos.org?
+
+You can configure this as a Nix substitutor on your systems like this:
+
+```nix
+  nix.settings.substituters = lib.mkForce [
+    "https://nixos.tvix.store"
+  ];
+```
+
+For store paths it hasn't already seen yet, it'll internally ingest its contents
+into tvix-castore (deduplicating in doing so).
+
+Requests for NARs will dynamically reassemble the NAR representation on demand.
+
+Metadata and signatures are preserved (which is why you don't need to add
+additional trusted keys).
+We need to produce the same data bit by bit, else the signature check in your
+Nix/Lix client would fail.
+
+Be however aware that there's zero availability guarantees.
+We will frequently redeploy this box, and it might become unavailable without
+prior notice.
+
+Tvix currently doesn't have garbage collection. If we run out of disk space, we
+might either move things to a bigger box or delete everything on it so far.
+
+As it's only a cache, it should however re-ingest things again.