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

2.1 KiB

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

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.