homelab-codex-ws/services/ollama-piha/README.md

# ollama-piha

Local CPU Ollama on **PIHA**, serving exactly one purpose: the **fallback embed
backend** for `kb-query` while SOLARIA (the GPU node, ~16 h/day powered off)
sleeps. Model: `bge-m3` — the **same** model as SOLARIA's Ollama, because query
embeddings must live in the same vector space as the pgvector index
(`document_chunk.embedding VECTOR(1024)`); a different/smaller model is not an
option (module 5 phase 4 plan §2 decision 2).

Expected latency: bge-m3 embeds in ~207 ms on SOLARIA's GPU vs ~790 ms on x86
CPU; on the Pi 5 expect single seconds per query (plus model load, since the
model is never resident — see below). Slower but alive beats fast but dead.

## Design constraints

- **`OLLAMA_KEEP_ALIVE=0`** (pinned in compose): PIHA is the RAM-bound 8 GB box
  shared with Home Assistant. The model is unloaded immediately after every
  call — a transient ~1.5–2 GB spike per embed, ~100 MB idle daemon, never a
  resident cost.
- **`mem_limit: 2560m`** (host override, `hosts/piha/runtime/ollama-piha/`):
  hard cgroup ceiling, plan §2 D2 starting value. The cgroup OOM killer
  restarts this container instead of the host OOM killer picking a victim
  (which could be Home Assistant). Confirm/trim after live calibration.
- **Bind**: `127.0.0.1` + `LAN_BIND_IP` (192.168.31.5) only — kb-query calls it
  over the host LAN interface (same pattern as kb-query → kb-postgres:5433).
  Never `0.0.0.0`, never a Tailscale bind, no public ingress.
- **Storage**: Docker named volume `ollama_piha_models` (NVMe data-root), not a
  bind mount — the ollama image runs as in-container root and would break
  PIHA's uid pattern (host oskar=1004, containers uid 1000, setgid group pi)
  if it wrote to a shared bind directory.

## Deploy (PIHA, master, after merge)

```bash
cd ~/homelab-codex-ws && git pull
cp services/ollama-piha/env.example services/ollama-piha/.env   # LAN_BIND_IP
docker compose -f services/ollama-piha/docker-compose.yml \
  -f hosts/piha/runtime/ollama-piha/docker-compose.override.yml \
  --env-file services/ollama-piha/.env up -d
```

**Then pull the model — this does NOT happen automatically:**

```bash
docker exec ollama-piha ollama pull bge-m3
```

Verify:

```bash
services/ollama-piha/healthcheck.sh          # checks container + API + bge-m3 present
time curl -s http://127.0.0.1:11434/api/embeddings \
  -d '{"model":"bge-m3","prompt":"test kalibracyjny"}' | head -c 80
```

(`deploy-node.sh` on PIHA also picks this service up from
`hosts/piha/services.yaml` once `.env` exists — the `ollama pull bge-m3` step
stays manual either way.)

## Calibration (plan §5 step 4 — gate, not formality)

Before trusting the fallback under load, on live PIHA at a normal (not
night-quiet) hour: run a few embeds as above while watching
`docker stats ollama-piha`, note peak RAM and wall time. Verdict per plan §5
step 5: keep as default fallback / tune `mem_limit` / fall back to explicit
503 degradation.

**Calibration status: measured 2026-07-27 — verdict GO** (live PIHA under
normal load, 3 consecutive `/api/embeddings` calls after `ollama pull bge-m3`;
full protocol in `docs/sessions/2026-07-27-kb-f4-fallback.md` §4):

- Latency: 5.25 s (cold start) / 4.41 s / 4.16 s — single seconds as expected,
  no warm-up between calls by design (`OLLAMA_KEEP_ALIVE=0` releases the model
  after every request, `ollama ps` shows nothing resident in between).
- RAM: idle ~66 MiB, burst peak ~983 MiB (`docker stats` sampled at 0.3 s) —
  well inside the 2560m ceiling; host `available` never dropped below ~1.3 GiB.
- Kept as **default fallback** (no feature flag). The measurement was taken
  against the same container configuration this repo deploys (image,
  `OLLAMA_KEEP_ALIVE=0`, `mem_limit: 2560m`), so it carries over; only the
  model storage differed (bind mount then, named volume now), which does not
  affect RAM/latency.

## Relation to kb-query

kb-query's router (`services/kb-query/app/embed_router.py`) health-checks
SOLARIA with a ~30 s cache and only sends embeds here while SOLARIA is down.
kb-query verifies at first use that this backend actually serves `bge-m3`
(`/api/tags`) and refuses to embed against a mismatched model. Configuration:
`EMBED_FALLBACK_URL=http://192.168.31.5:11434` in `services/kb-query/.env`.
See `services/kb-query/README.md` for the fallback verification plan (tests
A/B/C).