83 lines
3.8 KiB
Nix
83 lines
3.8 KiB
Nix
# Conservative, surgical Docker prune (Phase 2pc / PC1).
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#
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# REPLACES `virtualisation.docker.autoPrune` (which ran `docker system prune --force --all
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# --filter until=24h` daily). The `--all` removed every image NOT used by a *running* container —
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# between CI runs no test apps run, so it evicted the cached recipe base images and forced a cold
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# re-pull on the next run → the prune->re-pull->Docker-Hub-rate-limit churn documented in JOURNAL-2.
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#
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# On this single host, Docker's local image store is the CI cache. Keep tagged images during
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# routine pressure, but evict unused old images at 90% usage. This recovers from a warm service
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# crash loop: an unmet replica must not prevent the emergency cleanup that lets it restart.
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# Never prune volumes, and skip while a run-app stack is live.
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{ pkgs, ... }:
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let
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# `/` usage % at/above which a surgical prune is permitted. Below this: keep the cache, no-op.
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threshold = 80;
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emergencyThreshold = 90;
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prune = pkgs.writeShellApplication {
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name = "cc-ci-docker-prune";
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runtimeInputs = with pkgs; [ docker coreutils gnugrep gawk ];
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text = ''
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THRESH=${toString threshold}
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EMERGENCY_THRESH=${toString emergencyThreshold}
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used="$(df --output=pcent / | tail -1 | tr -dc '0-9')"
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: "''${used:=0}"
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if [ "$used" -lt "$THRESH" ]; then
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echo "docker-prune: / at ''${used}% (< ''${THRESH}%) — keeping local image cache, nothing to do"
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exit 0
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fi
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# NEVER prune mid-run: a live run-app stack means a deploy/test is in flight (mid-pull layers
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# can look prunable). Run-app services: <=4char>-<6hex>_<zone-stem>_* (lifecycle.py).
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# Zone stem matches BOTH ci_autonomic_zone (current) and ci_commoninternet_net
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# (legacy stacks from before the 2026-09 domain cutover) during the bake window.
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if docker service ls --format '{{.Name}}' \
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| grep -qE '^[a-z0-9]{1,4}-[0-9a-f]{6}_ci_(autonomic_zone|commoninternet_net)_'; then
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echo "docker-prune: a run-app stack is live — skipping (never prune mid-run)"
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exit 0
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fi
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if [ "$used" -ge "$EMERGENCY_THRESH" ]; then
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echo "docker-prune: / at ''${used}% (>= ''${EMERGENCY_THRESH}%) — emergency prune of unused images older than 7d"
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docker container prune -f --filter until=24h || true
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docker image prune -af --filter until=168h || true
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docker builder prune -f --filter until=24h || true
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df -h /
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exit 0
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fi
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# NEVER prune while ANY swarm service is converging (unmet replicas => a pull/deploy in flight,
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# including infra warm redeploys). Replicas field is "running/desired" e.g. 1/1.
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converging="$(docker service ls --format '{{.Replicas}}' \
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| awk -F/ '{ if (($1+0) != ($2+0)) c++ } END { print c+0 }')"
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if [ "$converging" -gt 0 ]; then
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echo "docker-prune: $converging service(s) converging (deploy/pull in flight) — skipping"
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exit 0
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fi
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echo "docker-prune: / at ''${used}% (>= ''${THRESH}%) — surgical prune (dangling + until=24h; NEVER --all/--volumes)"
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docker container prune -f --filter until=24h || true
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docker image prune -f --filter until=24h || true
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docker builder prune -f --filter until=24h || true
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df -h /
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'';
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};
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in
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{
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systemd.services.ci-docker-prune = {
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description = "Disk-pressure-gated Docker prune (old unused images at 90%; never volumes or mid-run)";
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after = [ "docker.service" ];
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requires = [ "docker.service" ];
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path = [ pkgs.docker ];
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serviceConfig = {
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Type = "oneshot";
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ExecStart = "${prune}/bin/cc-ci-docker-prune";
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};
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};
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systemd.timers.ci-docker-prune = {
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description = "Daily timer for the surgical Docker prune";
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wantedBy = [ "timers.target" ];
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timerConfig = {
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OnCalendar = "daily";
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Persistent = true;
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};
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};
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}
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