thermograph/backend/daemon/README.md
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daemon: move the Discord gateway and scheduler out of the web process into Go (#21)
The gateway bot and APScheduler were long-lived stateful I/O loops running
inside the async web app under a leader election. They move into a single Go
binary that owns ONLY that I/O -- websocket, RESUME, heartbeat, backoff, timers.

It owns no grading logic. Anything needing data calls back over a new
internal-only surface (/internal/discord/grade, /internal/jobs/*). Grading
depends on polars and the parquet cache; reimplementing it in Go would let the
bot's grades drift from the API's. The grade route returns gateway-ready JSON
and Go relays the bytes verbatim.

The binary ships in the backend image and runs as a second compose service off
the same tag, so the two ends of the /internal/* contract can never skew.
deploy.sh rolls daemon alongside backend -- without that the service would never
be created, since a single-service deploy uses --no-deps. It also probes the
image first and skips the daemon when rolling a tag that predates the binary:
infra tracks main while image tags are env-staged, so a host can legitimately be
asked to roll an older backend image, and creating the service anyway would
leave a container crash-looping on a missing binary.

replicas: 1 with order: stop-first replaces the leader election -- Discord
permits one gateway connection per bot token.

THERMOGRAPH_INTERNAL_TOKEN is optional: both ends derive it from
THERMOGRAPH_AUTH_SECRET via HMAC under a domain-separation label, so this needs
no new vault entry. The derivation is pinned to a shared cross-language test
vector asserted on both sides, so drift fails CI instead of 401ing every call.
Fail closed when neither secret is set.

Improvements over the Python: a close intended for RESUME uses 4000 rather than
1000 (Discord invalidates a session closed 1000, so the old default defeated its
own resume); MESSAGE_CREATE runs on a bounded worker pool; and a malformed HELLO
returns an error rather than a clean reconnect, which would otherwise reset
backoff and hot-loop against the gateway.

365 Python tests pass; Go build/vet/test -race clean; shellcheck 0 findings.
2026-07-23 22:49:54 +00:00

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# thermograph-daemon
Single Go binary that owns the backend's long-lived stateful I/O: the Discord
gateway connection (IDENTIFY/RESUME/heartbeat/reconnect backoff) and the
recurring-job timers (warm-cities, IndexNow). It replaces the two in-process
background jobs `web/app.py` used to run under leader election — one daemon
replica makes the single-connection invariant a deployment fact instead of a
runtime election.
## The Go/Python split
Go here owns **no** climate or grading logic. Grading depends on polars and the
parquet cache, and the slash-command path deliberately shares one grade builder
with the API so bot grades and API grades never drift. So anything data-shaped
is a POST back into the Python app's internal-only routes:
| Route | Purpose |
| --- | --- |
| `POST /internal/discord/grade` | `{"query": "phoenix"}` → gateway-ready Discord message JSON, relayed to Discord verbatim |
| `POST /internal/jobs/warm-cities` | trigger the warm-cities job |
| `POST /internal/jobs/indexnow` | trigger the IndexNow check-and-submit |
Every request carries `X-Thermograph-Internal-Token`. Caddy never routes
`/internal/*` to the backend, so the token is defence in depth, not the only
control. If `THERMOGRAPH_INTERNAL_TOKEN` is unset, the Python side disables the
routes and this daemon refuses to start (fail closed on both ends).
## Configuration (env)
| Var | Required | Meaning |
| --- | --- | --- |
| `THERMOGRAPH_INTERNAL_TOKEN` | yes | shared secret for the internal routes |
| `THERMOGRAPH_API_BASE_INTERNAL` | yes | backend base URL, e.g. `http://web:8137` |
| `THERMOGRAPH_DISCORD_BOT` | no | `1`/`true`/`yes`/`on` enables the gateway |
| `THERMOGRAPH_DISCORD_BOT_TOKEN` | no | bot token (gateway stays off without it) |
| `THERMOGRAPH_WARM_CITIES_INTERVAL_HOURS` | no | default 24; malformed → default |
| `THERMOGRAPH_INDEXNOW_INTERVAL_HOURS` | no | default 6; malformed → default |
## Run locally
```sh
cd backend/daemon
go build ./... && go vet ./... && go test ./...
THERMOGRAPH_INTERNAL_TOKEN=dev-token \
THERMOGRAPH_API_BASE_INTERNAL=http://localhost:8137 \
go run .
```
Deployed as `/usr/local/bin/thermograph-daemon` in the backend image.