Merge pull request 'feat(gitea-actions): act_runner capacity 2, dind sized for two concurrent jobs' (#146) from feat/runner-capacity-2 into main

Reviewed-on: #146

apps/wave-1/gitea-actions.yaml

@@ -77,6 +77,42 @@ spec:
     requests:
       storage: 1Gi
 ---
+# act_runner config file — DELTAS ONLY. act_runner v0.6.1 LoadDefault()
+# (internal/pkg/config/config.go) unmarshals this file onto a ZERO Config and then fills every
+# unset field with the same default it uses when there is no file at all, so a file holding
+# only `runner.capacity` changes exactly that and nothing else. Do NOT paste in the output of
+# `act_runner generate-config`: that example is NOT the defaults. Its `runner.labels` would
+# OVERRIDE the registered labels in /data/.runner (daemon.go: config labels win when non-empty)
+# and repoint ubuntu-latest at a different job image; its `force_pull: true` differs from the
+# no-file default (false); and its sample `envs` would be injected into every job.
+#
+# Using a file also makes act_runner IGNORE the legacy GITEA_RUNNER_CAPACITY / _FILE /
+# _ENVIRON / _ENV_FILE / GITEA_DEBUG / GITEA_TRACE env vars (deprecated.go). None of them is
+# set on this Deployment; the GITEA_INSTANCE_URL / _REGISTRATION_TOKEN / _NAME / _LABELS env
+# below is consumed by the image's run.sh for registration, not by that legacy path.
+#
+# A ConfigMap edit alone does NOT restart the runner (it reads the file once at start). If a
+# future change touches ONLY this ConfigMap, also bump the Deployment's pod template (e.g. the
+# config-revision annotation below) or the new value stays inert until the next restart.
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: act-runner-config
+  namespace: gitea-actions
+  labels:
+    app.kubernetes.io/name: act-runner
+data:
+  config.yaml: |
+    runner:
+      # Two concurrent jobs (default 1). Measured 2026-11-08: queue wait ~1s normally, but
+      # 29-759s whenever gate / images / renovate runs collide (run 472 waited 759s behind a
+      # renovate burst). Both jobs share the ONE dind daemon below; act_runner names each job's
+      # containers GITEA-ACTIONS-TASK-<task id> and creates a network per job, so they do not
+      # collide. Workflow `concurrency:` groups are enforced by Gitea server-side and are
+      # unaffected: gate.yml's gate-<ref> group still cancels a superseded run on the SAME ref,
+      # and renovate's group still serialises renovate. The dind resources are sized for TWO jobs.
+      capacity: 2
+---
 apiVersion: apps/v1
 kind: Deployment
 metadata:
@@ -95,6 +131,10 @@ spec:
     metadata:
       labels:
         app.kubernetes.io/name: act-runner
+      annotations:
+        # Bump when act-runner-config changes without any other pod-template change, so the
+        # Deployment rolls and act_runner re-reads its config (see the ConfigMap header).
+        homelab.keithjackson.dev/act-runner-config-revision: "1"   # capacity 2
     spec:
       # CI holds no cluster credentials — do not mount a SA token into the runner or
       # (via the shared netns) the job containers (R-SEC-02, docs/14).
@@ -146,12 +186,23 @@ spec:
               mountPath: /certs
             - name: dind-storage
               mountPath: /var/lib/docker
+          # Sized for runner.capacity: 2. Every job's containers run UNDER this daemon, so this
+          # container's cgroup carries the whole CI workload. Measured 2026-11-08 (Prometheus,
+          # capacity 1): peak CPU 0.69 core (1m rate, 30d), peak working set 447Mi (30d), 0 OOMs.
+          #   cpu request 2: two jobs at today's peak is ~1.4 core, and the gate is being
+          #     parallelised, so per-job demand rises. The request is what the CFS share is
+          #     weighted by under contention (100m was a 1/20 share); NO cpu limit, deliberately,
+          #     so an idle node's spare cores are still usable. k3s-prod-2 (8 CPU) had 2945m
+          #     requested; +1.9 core = ~4.85 (61%), and prod-1/prod-3 fit too if it reschedules.
+          #   memory request 1Gi / limit 4Gi: two jobs at today's peak is ~0.9Gi. An OOM kill here
+          #     takes down dockerd and with it BOTH running jobs, so the limit carries ~4x headroom
+          #     over that for the parallelised gate. Nodes have ~31Gi allocatable.
           resources:
             requests:
-              cpu: 100m
+              cpu: "2"
-              memory: 256Mi
+              memory: 1Gi
             limits:
-              memory: 2Gi
+              memory: 4Gi
           startupProbe:
             exec:
               command:
@@ -195,23 +246,36 @@ spec:
               value: /certs/client
             - name: DOCKER_TLS_VERIFY
               value: "1"
+            # The image's run.sh passes `--config <this>` to BOTH `act_runner register` and
+            # `act_runner daemon` when CONFIG_FILE is set (act_runner v0.6.1 scripts/run.sh).
+            - name: CONFIG_FILE
+              value: /etc/act_runner/config.yaml
           volumeMounts:
             - name: data
               mountPath: /data
             - name: certs
               mountPath: /certs
               readOnly: true
+            - name: config
+              mountPath: /etc/act_runner
+              readOnly: true
+          # Measured 2026-11-08 at capacity 1: peak CPU 0.24 core, peak working set 314Mi (30d)
+          # against the old 512Mi limit. It holds per-task state, log buffers and the embedded
+          # actions/cache server for every concurrent task, so the limit is doubled for capacity 2.
           resources:
             requests:
               cpu: 100m
-              memory: 128Mi
+              memory: 256Mi
             limits:
-              memory: 512Mi
+              memory: 1Gi
       volumes:
         - name: data
           persistentVolumeClaim:
             claimName: act-runner-data
         - name: certs
           emptyDir: {}
+        - name: config
+          configMap:
+            name: act-runner-config
         - name: dind-storage
           emptyDir: {}

decisions/2026-11-08-runner-capacity-2.md

@@ -0,0 +1,155 @@
+---
+date: 2026-11-08
+branch: feat/runner-capacity-2
+title: act_runner runs two jobs at once, and dind is sized for two
+---
+
+## What changed
+
+`apps/wave-1/gitea-actions.yaml` only. That file is a **hand-owned** non-catalog unit
+(`EXTRA_UNITS["gitea-actions"]` in `catalog/render.py`): the renderer only decides which wave
+it lands in, it does not generate its bytes, and `ci/render-golden.sh` compares only files the
+catalog renders. So it is edited in place, and no re-render was needed or run.
+
+1. **New ConfigMap `act-runner-config`** holding a config file with ONE key,
+   `runner.capacity: 2`, mounted read-only at `/etc/act_runner/` and selected with
+   `CONFIG_FILE=/etc/act_runner/config.yaml`. The image's `run.sh` (act_runner v0.6.1) turns
+   that into `--config` for both `register` and `daemon`.
+   - Deltas only, on evidence: v0.6.1 `LoadDefault()` unmarshals the file onto a zero Config and
+     then applies the same defaults as the no-file path, so the other settings are unchanged.
+   - The `generate-config` example was deliberately NOT used. Its `runner.labels` would override
+     the registered labels in `/data/.runner` and repoint `ubuntu-latest` at
+     `docker.gitea.com/runner-images`. Its `force_pull: true` is not the default. Its sample `envs`
+     would be injected into every job.
+   - With a file present, act_runner ignores the legacy `GITEA_RUNNER_CAPACITY` /
+     `_FILE` / `_ENVIRON` / `_ENV_FILE` / `GITEA_DEBUG` / `GITEA_TRACE` env vars. None of
+     them is set on this Deployment.
+2. **Pod-template annotation `homelab.keithjackson.dev/act-runner-config-revision: "1"`.**
+   act_runner reads its config once, at start, so a change to the ConfigMap alone would never
+   take effect. Bump this annotation whenever you change only the ConfigMap.
+3. **dind resources:** requests `cpu 100m -> 2` and `memory 256Mi -> 1Gi`; limit
+   `memory 2Gi -> 4Gi`. There is still no CPU limit, on purpose.
+4. **runner resources:** request `memory 128Mi -> 256Mi`, limit `memory 512Mi -> 1Gi`. CPU stays
+   at `100m`.
+
+Why these sizes. Measured 2026-11-08 through Prometheus, at capacity 1:
+
+| container | peak CPU (1m rate, 30d) | peak working set (30d) | OOM events (7d) |
+|---|---|---|---|
+| dind | 0.69 core | 447 MiB | 0 |
+| runner | 0.24 core | 314 MiB | 0 |
+
+At the moment of measurement the pod was idle (`top`: dind 1m/138Mi, runner 1m/83Mi), on
+k3s-prod-2.
+
+- **CPU request 2.** Two jobs at today's peak is about 1.4 cores. The gate is being parallelised
+  in other work, so each job will use more than that. The request sets dind's CFS weight under
+  contention; at 100m it got a 1/20 share. With no limit, dind can still use spare cores on an
+  idle node.
+- **Memory 1Gi / 4Gi.** Two jobs at today's peak is about 0.9 GiB. If dind is OOM-killed,
+  dockerd goes down and takes both running jobs with it, so the limit is about 4x that.
+- **Runner limit 512Mi -> 1Gi.** Its 30-day peak was already 61% of the old limit, and with
+  capacity 2 it holds state for two tasks.
+
+Scheduling headroom: CPU requests per node were measured with `describe node`. The pod's total
+CPU request goes from 200m to 2100m (+1.9 cores).
+
+| node | CPU requested now | after the change | allocatable |
+|---|---|---|---|
+| prod-2 (current) | 2945m | ~4845m (61%) | 8 |
+| prod-1 | 3175m | ~5075m | 8 |
+| prod-3 | 3840m | ~5740m (72%) | 8 |
+
+The pod fits on any of the three if the RWO PVC moves it.
+
+Concurrency semantics. Workflow `concurrency:` groups are enforced by Gitea on the server, not by
+the runner, so capacity does not change them:
+
+- `gate.yml` `gate-${{ github.ref }}` with cancel-in-progress still cancels a superseded run on
+  the same ref.
+- `renovate` (group `renovate`, no cancel) and `images-${{ github.ref }}` still serialise
+  themselves.
+
+What capacity 2 does change: runs on *different* refs (a PR gate next to a renovate or images
+run, or two PRs) now run side by side instead of queueing. The required check
+`gate / gate (pull_request)` is still one job per PR head, and gate.yml's other job
+(`conformance`) is `if: false`, so it never runs.
+
+Both jobs share one dockerd. act_runner gives each task its own container prefix
+(`GITEA-ACTIONS-TASK-<task id>`) and its own network, and no workflow uses fixed container names
+or host ports.
+
+## What I verified
+
+- **Source of truth.** `catalog/render.py` `EXTRA_UNITS` places `gitea-actions.yaml` by
+  anchor/offset only. `ci/render-golden.sh` iterates over rendered files only, so this file is
+  outside render==golden. No `--emit-waves` was run.
+- **act_runner v0.6.1 behaviour, read in its source** (tag v0.6.1):
+  - `config.LoadDefault()` treats a partial file as described above.
+  - `daemon.go`: config labels override `.runner` labels only when non-empty.
+  - `poller.go`: a semaphore of `cfg.Runner.Capacity` bounds concurrent tasks.
+  - `runner.go`: per-task container name prefix.
+  - The image's `run.sh`, read from `gitea/act_runner:0.6.1`, honours `CONFIG_FILE`.
+- **The live pod has no config file today.** `/data` holds only `.runner` and `lost+found`.
+  `act_runner --version` reports v0.6.1. No LimitRange or ResourceQuota exists in
+  `gitea-actions`.
+- **Resource numbers.** All figures above come from read-only `kubectl top`, `describe node` and
+  Prometheus queries against k3s-prod.
+- **dind disk.** The emptyDir sits on the node's 11.8G ephemeral filesystem: 4.0G used, 7.2G
+  free. Image cache is 2.18GB, which is the one `catthehacker/ubuntu:act-22.04` image. Two
+  concurrent jobs share that image.
+- **Embedded config.** It parses as YAML to `{'runner': {'capacity': 2}}`. The only `$` in the
+  manifest is the existing `${BASE_DOMAIN}`, so nothing new is exposed to Flux postBuild
+  envsubst.
+- **Approval policy.** `apps/wave-1/` matches no `sensitive_paths` glob in
+  `infra/gitea/approval-policy.json`, so this PR merges on a green gate alone.
+- **Local gate.** Pinned toolbox, run from the worktree on the committed tree. The rc and skipped
+  stages are given in the PR description.
+
+## What I did NOT verify
+
+- **UNVERIFIED: that the runner actually starts with the config and runs two jobs at once.**
+  Nothing is applied until Flux reconciles `main`.
+- **Capacity cannot be seen through Gitea's API.** act_runner v0.6.1 does not report capacity to
+  Gitea: `Declare` sends only version and labels. `GET /api/v1/admin/actions/runners` therefore
+  cannot show "capacity 2". Concurrency has to be observed instead.
+- **UNVERIFIED: whether the parallelised gate fits in these sizes.** That gate has not landed.
+  Re-measure after it does, with
+  `max_over_time(sum by (container)(rate(container_cpu_usage_seconds_total{namespace="gitea-actions"}[1m]))[7d:30s])`.
+- **Rollout cancels in-flight jobs.** The rollout restarts the runner pod (strategy Recreate,
+  `shutdown_timeout: 0s`), and any job running at that moment is cancelled, possibly including
+  the `push`-to-main gate run triggered by this very merge. Re-run it if that happens.
+- **dind disk is not bounded by a limit.** With two jobs it holds two jobs' workspaces and layers
+  on the same 11.8G node filesystem. I did not add an `ephemeral-storage` limit, because an
+  eviction would kill both jobs. Watch kubelet DiskPressure on the runner's node.
+- **Stale comments in sensitive paths.** `.gitea/workflows/gate.yml` (line ~52) and
+  `.gitea/workflows/README.md` (line ~86) still say "`act_runner` runs at capacity 1". I left
+  them alone because `.gitea/**` is a sensitive path and editing them would put this PR behind
+  human approval. Fix them in a separate PR.
+
+### Operator post-merge checklist
+
+1. Flux applied it:
+   `kubectl --context k3s-prod -n flux-system get kustomization apps-wave-1 -o jsonpath='{.status.lastAppliedRevision}'`
+   equals the merge commit.
+2. The pod restarted with the config:
+   - `kubectl --context k3s-prod -n gitea-actions get pod -l app.kubernetes.io/name=act-runner`
+     shows a new pod, 2/2 Running.
+   - `kubectl ... exec deploy/act-runner -c runner -- cat /etc/act_runner/config.yaml` shows
+     `capacity: 2`.
+   - `kubectl ... exec deploy/act-runner -c runner -- ps` shows `act_runner daemon --config /etc/act_runner/config.yaml`.
+   - The logs show "declare successfully" with the two expected labels (`ubuntu-latest`,
+     `homelab` -> `catthehacker/ubuntu:act-22.04`). That confirms the labels did not change.
+3. The runner is registered and online:
+   - `GET /api/v1/admin/actions/runners` lists `incluster-dind`, online, with the same ID as
+     before (no duplicate row).
+   - Capacity is NOT shown there; see above.
+4. Concurrency is real: trigger two runs on different refs (e.g. two PR gates, or a PR gate plus a
+   `workflow_dispatch` of renovate). Then either:
+   - in `GET /api/v1/repos/Home-Network/home-network-k3s-impl/actions/tasks`, confirm their
+     `run_started_at` .. `updated_at` windows overlap; or
+   - check
+     `docker --host=tcp://127.0.0.1:2376 --tlsverify ... ps` in the dind container lists two
+     `GITEA-ACTIONS-TASK-*` container sets at once.
+5. Resources: `kubectl --context k3s-prod -n gitea-actions describe pod` shows dind requests
+   cpu 2 / memory 1Gi, limit memory 4Gi, and runner limit memory 1Gi.