## nod

A simple daemon that collects Nix build and substitution statistics using structured JSON logs.

## requirements

- Nix 2.30 or later (`json-log-path` support)

## building

```bash
cargo build --release
```

## usage

Start the daemon:

```bash
nod daemon
```

Point Nix at the socket in `nix.conf`:

```
json-log-path = /run/user/1000/nod/nod.sock
```

Then use Nix normally. View accumulated stats with:

```bash
nod stats          # all time
nod stats -d 7     # last 7 days
nod stats -m 3     # last 3 months
nod stats -y 1     # last year
nod clean          # reset the database
```

## configuration

| flag | env | default |
|------|-----|---------|
| `--socket` | `NOD_SOCKET` | `$XDG_RUNTIME_DIR/nod/nod.sock` |
| `--db` | `NOD_DB` | `$XDG_DATA_HOME/nod/nod.db` |

Both directories are created automatically. The socket path in `nix.conf` must match `--socket`.

## how?

Nix 2.30 added `json-log-path`, which writes a stream of structured activity events (start/result/stop) to a file or Unix socket while a build runs. nod listens on that socket, tracks in-flight activities by ID, and on each stop event inserts a completed row into a local SQLite database. `nod stats` queries that database through the daemon.

Relevant Nix source: [logging.hh](https://github.com/NixOS/nix/blob/b4de973847370204cf28fe2092abdd21f25ee0e8/src/libutil/include/nix/util/logging.hh)