# Configuration

Every setting comes from the environment, or from an env file. Which file
depends on how the installation was started:

| Started with | Reads |
|---|---|
| `fluksio serve` | `env` inside the data directory (`$FLUKSIO_ENV_FILE`) |
| the Docker stack | `.env` beside `docker/` |

Anything already exported wins over the file.

## Storage

| Variable | Default | Notes |
|---|---|---|
| `DATA_DIR` | `flow-data` (`./.fluksio` via the CLI; `~/.fluksio` with `--global`) | everything below derives from this |
| `DATABASE_URL` | SQLite in `DATA_DIR` | any SQLAlchemy URL |
| `FLOWS_DIR` | `$DATA_DIR/flows` | the git repository holding flows |
| `SECRETS_FILE` | `$DATA_DIR/secrets.enc` | encrypted credentials, deliberately outside the repo |
| `ALERTS_FILE` | `$DATA_DIR/alerts.json` | channels and rules |
| `PROVISIONERS_FILE` | `$DATA_DIR/provisioners.json` | clusters a machine can be started from; absent means none |
| `PANELS_FILE` | `$DATA_DIR/panels.json` | wall-panel pairings |
| `OAUTH_PRIVATE_KEY_FILE` | `$DATA_DIR/oauth-key.pem` | signs agent and worker tokens |
| `CLOUD_CONFIG_FILE` | `$DATA_DIR/cloud.json` | the portal enrolment, if any |
| `NODE_VENV` | `auto` | which interpreter node code runs on — see below |

Set `DATA_DIR` and the rest follow. Set one explicitly and it wins — which is
what the container images do to pin everything onto `/data`.

`NODE_VENV` is the exception, being about an environment rather than a path:

| Value | What node code runs on |
|---|---|
| `auto` (default) | the venv Fluksio was installed into, when it was installed into one and there is no venv of its own already built. `pip install fluksio` beside your own packages is this case, and the packages are then already there — the Modules screen turns read-only, because that environment is not Fluksio's to install into. |
| `managed` | a venv the engine builds under `DATA_DIR` and owns, which the Modules screen installs into with `uv pip sync`. The container images set this: the venv in them holds the app and nothing of anybody else's. |
| a path | that interpreter, or that venv, whatever it is. |

An installation that already has a managed venv keeps it on upgrade under
`auto`, because it may hold packages somebody installed on purpose.

!!! warning "The four files that must be on persistent storage"

    `secrets.enc`, `alerts.json`, `panels.json` and `oauth-key.pem` are written
    at runtime. In a container, anything not on a volume lands in the writable
    layer and is lost on the next rebuild — un-pairing every screen and
    revoking every agent.

## State

| Variable | Default | Notes |
|---|---|---|
| `REDIS_HOST` | unset | without it, flow state lives in memory and does not survive a restart |
| `REDIS_PORT` | `6379` | |

Flow state is the last value of every message, node memory, and the run queue.
Redis here is persistence, not a cache — run it with append-only persistence
on.

## Identity and access

| Variable | Default | Notes |
|---|---|---|
| `SECRET_KEY` | generated | signs sessions and derives the secrets-store key |
| `ACCESS_TOKEN_EXPIRE_MINUTES` | `11520` (8 days) | |
| `FIRST_SUPERUSER` | — | absent means the CLI creates one on first run |
| `FIRST_SUPERUSER_PASSWORD` | — | absent means one is generated and printed once |
| `DOMAIN` | `localhost` | what the API and OAuth issuer are built from |
| `FRONTEND_HOST` | `http://localhost:5173` | used in mails, OAuth metadata and panel pairing links |
| `BACKEND_CORS_ORIGINS` | `[]` | comma-separated; `FRONTEND_HOST` is always allowed |

## Where the interface looks for the API

The dashboard is a static bundle, so this one is a **build** argument of the
`frontend` image rather than a setting the running stack reads.

| Argument | Used by | Effect |
|---|---|---|
| `VITE_API_URL` | `frontend` at build time | the address the interface calls |

The compose stack takes it from `.env`, falling back to `https://api.${DOMAIN}`.
`scripts/setup.sh` writes it there with the scheme `ENVIRONMENT` implies, so a
local build calls `http://` and does not fail a certificate check nothing is
there to satisfy.

Empty is the useful value: the interface then addresses the API relative to
whichever origin served the page, so one image answers on a hostname, on a
`http://<host-ip>:<port>`, and through an ssh tunnel alike — and no origin has
to be added to `BACKEND_CORS_ORIGINS`, because there is only one.
`docker/compose.lan.yml` builds it that way and puts an `/api` proxy in front
of the backend to complete it; see
[getting started](../getting-started/facility-automation.md#on-your-own-network-by-address).

Set it to an absolute URL only when the API genuinely lives somewhere else, and
remember it is fixed at build time: changing it means rebuilding that image.

!!! danger "Rotating `SECRET_KEY`"

    The secrets store is encrypted with a key derived from it. Change it and
    the store stops decrypting, and every session is signed out. Re-enter your
    secrets, or plan the rotation properly.

## Environment

| Variable | Default | Notes |
|---|---|---|
| `ENVIRONMENT` | `local` | `local`, `staging` or `production` |
| `PRIVATE_API_ENABLED` | `false` | unauthenticated test-only endpoints; needs `ENVIRONMENT=local` too |
| `TZ` | `UTC` | the timezone every schedule is written in |

`TZ` is the container's own, not a setting the code reads: an `inject` or a
`delay` with a cron expression fires on local time. Left at `UTC`, "off at
02:00" means two in the morning UTC, which in most of the world is neither two
o'clock nor the same hour in summer as in winter. Set it to where the
installation is.

`production` closes `/docs`, `/redoc` and the OpenAPI document, because the
schema enumerates every endpoint the installation serves — including the paths
webhook nodes mounted at runtime. It also turns a `changethis` secret from a
warning into a refusal to start.

## The engine

| Variable | Default | Notes |
|---|---|---|
| `FLOW_MAX_WORKERS` | `4` | node-code subprocesses run in parallel |
| `FLOW_MAX_CASCADES` | `4` | cascades in flight at once; throughput is this over the mean cascade time, so raise it where nodes wait on a network rather than a CPU |
| `FLOW_MAX_RUNS` | `4` | batch runs driven at once. A different limit from the one above: a run drives a whole graph, and its nodes are bounded by `FLOW_MAX_WORKERS`. This is what a sweep queues behind |
| `FLOW_NODE_TIMEOUT` | `0` | seconds a node may be silent, unless it sets its own; 0 is no limit |
| `FLOW_CPUS` | `0` | cores nodes that declare `resources` may be given; 0 works it out as every core but two, which are what keeps the engine answering while the machine is busy |
| `FLOW_GPUS` | `0` | GPUs on this machine, each held by one node at a time. Not detected — say how many there are |
| `OBS_RETENTION_DAYS` | `30` | how long metrics, events and run records are kept |
| `ARTIFACT_GC_INTERVAL_S` | `3600` | how often artifact bytes nothing refers to are swept away; 0 never sweeps |
| `ARTIFACT_GC_GRACE_S` | `3600` | how long a freshly written artifact is spared, whatever refers to it |

The three concurrency limits are also flags on `fluksio serve` — `--max-workers`,
`--max-cascades`, `--max-runs` — which outrank the file, and the engine says
which numbers it started with in its first lines.

An artifact is referred to by a run that recorded it or by a message currently
holding it; anything else is what a camera published four hours ago, and the
sweep is what keeps a flow streaming media from filling the disk. It stands
aside entirely while a run is in flight, since a node may store a checkpoint
long before it returns the reference to it.

A node that declares nothing is not accounted against `FLOW_CPUS`; it runs on
the shared pool and is given `FLOW_CPUS / FLOW_MAX_WORKERS` as a thread cap, so
several at once cannot each size themselves to the whole machine. Setting
`OMP_NUM_THREADS` (or any of its siblings) on the engine yourself overrides
that default.

These two are this machine's figures. An attached worker reports its own when
it dials in, and a node goes to whichever machine can grant what it asked for —
so a GPU on a worker needs no `FLOW_GPUS` here. What every machine has free, and
which nodes are queued, is `GET /api/v1/workers/resources` and the Workers
screen. Named sizes live in the database and are `GET /api/v1/flavors`;
`PROVISIONERS_FILE` is where machines can be started from. See
[declaring resources](../getting-started/data-science.md#declaring-what-a-node-needs).

## Agents

| Variable | Default | Notes |
|---|---|---|
| `MCP_ENABLED` | `false` | opens the `/mcp` endpoint **and** OAuth client registration |
| `MCP_TOKEN_EXPIRE_MINUTES` | `60` | an agent's token is a bearer secret held by a program |
| `MCP_REFRESH_EXPIRE_DAYS` | `30` | |
| `OAUTH_CODE_EXPIRE_SECONDS` | `60` | |

See [Agents over MCP](../code/agents.md).

## Mail

Needed for password-reset mails. Without `SMTP_HOST` and `EMAILS_FROM_EMAIL`,
mail is simply off.

| Variable | Default |
|---|---|
| `SMTP_HOST` | — |
| `SMTP_PORT` | `587` |
| `SMTP_USER` / `SMTP_PASSWORD` | — |
| `SMTP_TLS` / `SMTP_SSL` | `true` / `false` |
| `EMAILS_FROM_EMAIL` | — |
| `EMAILS_FROM_NAME` | `Fluksio` |
| `EMAIL_RESET_TOKEN_EXPIRE_HOURS` | `48` |

## Monitoring

| Variable | Default | Notes |
|---|---|---|
| `SENTRY_DSN` | — | error reporting, if you want it |

## Health check

`GET /api/v1/utils/health/` is a *deep* check: it fails when the event loop is
wedged or the state backend is gone, not just when the process is up. That is
what the container healthcheck probes, and what an autoheal sidecar restarts
on.

## See also

- [The `fluksio` command](../code/cli.md) — what the data directory holds
- [Getting started: facility automation](../getting-started/facility-automation.md)