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fix(deploy/push-cache): push build-time deps too, not just runtime closure

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cachix push by default only walks the RUNTIME closure of the paths it
gets on stdin. Build-time inputs like fetchPnpmDeps tarballs are
consumed during a build and then thrown away — never referenced from
the final output — so they never make it into the cache.

This bites when an ATM has the cached runtime output for an older
version of bitspire-atm-app but then needs to rebuild it (e.g. because
a flake.nix change shifts the toplevel hash, cascading through to a
new app derivation). Sintra OOM-killed itself today (2026-05-25) doing
exactly this: 1.4 GB of pnpm install + node-headers on 1 GB of RAM.

Fix: query the .drv that produced each output path, then walk
`nix-store -qR --include-outputs <drv>` — that gives the full
build-time closure (every path needed to realize the build, including
fixed-output fetchers like fetchPnpmDeps). cachix push then uploads
all of them.

Cost: somewhat larger pushes, but the dev box has the headroom.
Benefit: ATM nixos-upgrade never falls into the rebuild-from-source
trap.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Padreug 2026-05-25 13:16:23 +02:00
commit f589b1c078
1 changed files with 16 additions and 2 deletions
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18
deploy/push-cache.sh
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@ -29,8 +29,22 @@ build_and_push() {
local attr="$2"
echo "==> Building $name ($attr)..."
nix build ".#$attr" --no-link --print-out-paths | cachix push "$CACHE"
echo "==> Pushed $name to $CACHE.cachix.org"
local out_paths
out_paths=$(nix build ".#$attr" --no-link --print-out-paths)
# Walk the BUILD-TIME closure (not just runtime) so derivations like
# `bitspire-atm-app-pnpm-deps` (fetchPnpmDeps tarball, consumed only
# during the app's build and discarded) land in the cache. Without
# this, ATMs that need to rebuild the app from source — i.e. any time
# `cachix push` already-cached the runtime output but a downstream
# eval needs a new toplevel that re-derives the app — would OOM-kill
# themselves trying to run `pnpm install` locally on 1 GB of RAM.
# OOM caught on Sintra 2026-05-25 with the 1.4 GB pnpm-deps build.
local drvs
drvs=$(echo "$out_paths" | xargs -r -n1 nix-store -q --deriver)
echo "$drvs" | xargs -r nix-store -qR --include-outputs | cachix push "$CACHE"
echo "==> Pushed $name (runtime + build-time closure) to $CACHE.cachix.org"
}
case "$target" in