docs: atticd cache

2026-06-05 13:42:17 +00:00
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+# Using the `hectic` Attic Cache
+
+This document explains how to:
+
+1. pull build artifacts from the cache
+2. push new artifacts to the cache
+3. configure this flake to use the cache
+
+## Cache endpoints
+
+- API endpoint: `https://cache.hectic-lab.com`
+- Binary cache endpoint: `https://cache.hectic-lab.com/hectic`
+
+The `hectic` cache is:
+
+- public for reads
+- private for pushes
+
+## Requirements
+
+Use the Attic client package:
+
+```sh
+nix shell nixpkgs#attic-client
+```
+
+Or run commands directly with:
+
+```sh
+nix shell nixpkgs#attic-client -c <command>
+```
+
+## Read from the cache
+
+### Get the cache public key
+
+```sh
+nix shell nixpkgs#attic-client -c attic cache info hectic
+```
+
+Copy the `Public Key` value, which looks like:
+
+```text
+hectic:...
+```
+
+### Configure Nix to trust the cache
+
+Per-user: `~/.config/nix/nix.conf`
+
+```ini
+substituters = https://cache.nixos.org https://cache.hectic-lab.com/hectic
+trusted-public-keys = hectic:PASTE_PUBLIC_KEY_HERE
+```
+
+System-wide: `/etc/nix/nix.conf`
+
+```ini
+substituters = https://cache.nixos.org https://cache.hectic-lab.com/hectic
+trusted-public-keys = hectic:PASTE_PUBLIC_KEY_HERE
+```
+
+After that, normal Nix commands can download from the cache automatically:
+
+```sh
+nix build .#migrator
+nix develop
+nix flake check
+```
+
+## Use the cache from this flake
+
+You can also advertise the cache from `flake.nix`:
+
+```nix
+nixConfig = {
+  extra-substituters = [
+    "https://cache.nixos.org"
+    "https://cache.hectic-lab.com/hectic"
+  ];
+  extra-trusted-public-keys = [
+    "hectic:PASTE_PUBLIC_KEY_HERE"
+  ];
+};
+```
+
+Then users can run:
+
+```sh
+nix build --accept-flake-config .#migrator
+```
+
+## Log in for pushing
+
+Pushing requires an Attic token.
+
+```sh
+nix shell nixpkgs#attic-client -c attic login local https://cache.hectic-lab.com "<TOKEN>"
+```
+
+Example with `pass`:
+
+```sh
+nix shell nixpkgs#attic-client -c attic login local https://cache.hectic-lab.com "$(pass show atticd/hectic-lab/token)"
+```
+
+## Push build results
+
+### Push a package
+
+```sh
+nix build .#migrator
+nix shell nixpkgs#attic-client -c attic push local:hectic ./result
+```
+
+### Push a check
+
+```sh
+nix build .#checks.x86_64-linux.arguments
+nix shell nixpkgs#attic-client -c attic push local:hectic ./result
+```
+
+### Push a NixOS system build
+
+```sh
+nix build '.#nixosConfigurations."hectic-lab|x86_64-linux".config.system.build.toplevel'
+nix shell nixpkgs#attic-client -c attic push local:hectic ./result
+```
+
+## Recommended workflow
+
+### Local development
+
+Use the cache for reads only:
+
+```sh
+nix build .#migrator
+nix develop
+nix flake check
+```
+
+### CI / builder
+
+1. Build
+2. Push to Attic
+
+Example:
+
+```sh
+nix build .#migrator
+nix shell nixpkgs#attic-client -c attic push local:hectic ./result
+```
+
+## Useful commands
+
+### Show cache info
+
+```sh
+nix shell nixpkgs#attic-client -c attic cache info hectic
+```
+
+### Check login config
+
+```sh
+nix shell nixpkgs#attic-client -c attic cache info local:hectic
+```
+
+### Re-login with a new token
+
+```sh
+nix shell nixpkgs#attic-client -c attic login local https://cache.hectic-lab.com "<NEW_TOKEN>"
+```
+
+## Common issues
+
+### `flake 'nixpkgs' does not provide attribute 'attic'`
+
+Use:
+
+```sh
+nix shell nixpkgs#attic-client
+```
+
+Not:
+
+```sh
+nix shell nixpkgs#attic
+```
+
+### `HTTP 413 Payload Too Large`
+
+This means nginx rejected the upload body size. The server must allow large uploads on the Attic vhost.
+
+### Push succeeds for some paths but fails for others
+
+Usually means:
+
+- nginx body size limit
+- timeout/reverse proxy issue
+- bad token permissions
+
+### Cache pulls do not work
+
+Check:
+
+- `substituters`
+- `trusted-public-keys`
+- the exact public key from `attic cache info hectic`
+
+## Notes about retention and storage
+
+- The cache currently uses Hetzner Object Storage
+- If no `retention-period` is configured, cached objects do not expire automatically
+- This is good for long-lived reuse, but storage usage can grow over time
+
+## Summary
+
+### Read access
+
+```sh
+nix build .#migrator
+```
+
+after configuring:
+
+```ini
+substituters = https://cache.nixos.org https://cache.hectic-lab.com/hectic
+trusted-public-keys = hectic:PASTE_PUBLIC_KEY_HERE
+```
+
+### Push access
+
+```sh
+nix shell nixpkgs#attic-client -c attic login local https://cache.hectic-lab.com "<TOKEN>"
+nix build .#migrator
+nix shell nixpkgs#attic-client -c attic push local:hectic ./result
+```