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# meta-core
Standalone Go service that owns the metadata store (an embedded SQLite file),
the HTTP+SSE metadata surface, the
User Data Layer store and signing keystore, and a WebDAV file server for the
MetaMesh dev/prod stack.
## Overview
meta-core runs as its own container (`metacore-app`). Other MetaMesh services
(meta-sort, meta-fuse, meta-stremio, meta-dup, meta-search, meta-share,
meta-gateway, meta-watch, …) locate it over UDP multicast (beacon v2 —
its `metamesh.core` advertise carries the full `/urls` payload) and then call its
HTTP API. `META_CORE_URL` on a client pins it instead. The store is embedded
in the Go binary (no database port at all) — all metadata I/O is mediated by the HTTP/SSE API
(see [`docs/api-mediated-access.md`](docs/api-mediated-access.md)).
### Key capabilities
| Feature | Description |
|---------|-------------|
| **DB-file mutex** | Bash `flock` loop in `docker/leader-election.sh` only `exec`s supervisord on the winner, so two containers sharing one `/meta-core` volume can never run two writers on the database file. It is a mutex, not discovery — nothing reads the lock. |
| **Embedded SQLite store** | One schema-free `kv(k, v)` table in `/meta-core/db/meta-core.db` (pure-Go `modernc.org/sqlite`, WAL, `synchronous=NORMAL`). One writer goroutine with group commit; a record write (fields + root index + CID aliases + FTS row + events) is atomic. Replaced Redis in 2026-10 (Redis + the in-memory search copy needed ~6.6 GB on watch.nsl.sh's 169k records; the SQLite file is ~2.5 GB on disk with a bounded page cache). |
| **HTTP API** | Typed REST surface (gorilla/mux) for metadata, KV browsing, snapshots, schema inference, mounts, watchers, neighbours, identity, UDL, and file access by CID. |
| **Indexed search** | `POST /api/metadata/search` builds a superset of candidates in SQL — a partial expression index `kv_field` over (field name, value) of every record key, plus an FTS5 trigram table — then verifies each with the unchanged Go matchers. Fresh immediately, no in-memory copy (`internal/storage/search.go`, `internal/api/search_index.go`). |
| **SSE event streams** | `/api/events/files` and `/api/events/meta` mirror the store's `file:events` / `meta:events` streams so external services never touch the store. `meta:events` entries are written in the same transaction as the change. |
| **WebDAV server** | `/webdav/*` exposes the `/files` volume (read+write) for cross-service file access. nginx in front of meta-core handles caching. |
| **Service discovery** | beacon v2: UDP multicast advertise/listen on `239.255.99.1:9099`, neighbours served at `/neighbors`. The file-based registry under `/meta-core/services/*.json` it replaced is gone. |
| **File watcher / scanner** | Recursive scan + MidHash256 computation; emits events on `file:events`. Watched roots are POSTed watcher configs (`/meta-core/watchers.json`), not env vars. |
| **Mount management** | rclone-only mount manager (SMB rendered into `:smb:`, plus pre-defined remotes). Read-only by construction. |
| **UUID-rooted storage** | Roots are UUIDv7 (Crockford Base32, ULID layout); CIDs are reverse-index aliases. Schema-version sentinel refuses to boot against stale data. |
| **Identity keystore** | Multi-account secp256k1 signing keys under `/meta-core/identity/accounts/`, created from the dashboard's Identity menu (never auto-generated). A private key is returned only by generate, or by reveal against a proof-of-possession signature (delete needs the same proof); `/api/identity/sign` refuses challenge-domain payloads. |
| **User Data Layer** | Version-gated store for per-user signed (and, for private-tier keys, encrypted) records — My List, Continue Watching, ratings — indexed by user and CID. meta-core never inspects the crypto. See [User Data Layer](../../docs/project-architecture/user-data-layer.md). |
| **Dashboard + editor** | nginx serves a React dashboard at `/` and the standalone metadata editor at `/editor/`. |
### Design characteristics
- **Single writer** — flock on the `/meta-core` volume; no external consensus.
- **HTTP-only externally** — there is no database port; debug read-only with
`docker exec metacore-app sqlite3 -readonly /meta-core/db/meta-core.db …`
(dev stacks: `/meta-core-db/meta-core.db`).
- **Schema-gated boot** — `EnsureSchemaVersion` aborts startup when the
on-disk store layout predates the current build (alpha clean-wipe policy;
see `docs/uuid-rooted-metadata.md`).
- **Static binary** — CGO disabled (pure-Go SQLite), single Go binary plus a
thin Alpine image with `rclone`, nginx, supervisord and the `sqlite` CLI
(for debugging).
## Architecture
```
┌──────────────────────────────────────────────────────────────────────────┐
│ metacore-app (standalone container) │
│ │
│ leader-election.sh (flock /meta-core/locks/kv-leader.lock, │
│ then exec supervisord) │
│ supervisord │
│ ├─ nginx :80 (dashboard, /editor, API proxy, │
│ │ proxy_cache for /webdav, rclone GUI /rclone) │
│ ├─ rclone rcd (mount daemon, RC API on :5572) │
│ ├─ mount-watcher.sh (rclone mount lifecycle) │
│ └─ meta-core (Go) ─► HTTP API + SSE + WebDAV on :9000 │
│ ─► embedded SQLite (db/meta-core.db) │
│ ─► UDP advertise/listen 239.255.99.1:9099 │
└──────────────────────────────────────────────────────────────────────────┘
│
┌──────────────────────┴──────────────────────┐
│ /meta-core (meta-core's own volume) │
│ locks/kv-leader.lock │
│ db/meta-core.db (+ -wal, -shm) │
│ identity/accounts/*.json │
│ mounts/{mounts.json, errors/} │
│ watchers.json │
│ cache/ (nginx proxy_cache) │
└─────────────────────────────────────────────┘
meta-sort / meta-fuse / meta-stremio / meta-search / meta-share / …
│ 1. hear the metamesh.core advertise on UDP multicast (carries /urls)
└─ 2. HTTP + SSE (+ WebDAV) to metacore-app — never the store, never the volume
```
## Quick start
### Build
```bash
make build # build static binary to bin/meta-core
make docker # build container image as meta-core:1.0.0 + :latest + :local
make test # run Go unit tests
```
`make docker` tags the image as `:1.0.0`, `:latest`, **and** `:local`. The
`:local` tag is the one the sub-stack docker-compose files reference
(meta-share federation, meta-read and meta-listen dev stacks); the meta-gateway
dev stack (`docker-compose.gateway.yml`) uses `:latest`. Without these tags the
sub-stacks can't see a freshly-built image by name.
> **Source-change → recreate.** `make docker` rebuilds and re-tags the
> image, but **already-running containers stay on the old image SHA** —
> `docker compose up -d` won't recreate them unless the compose file
> itself changed. After a meta-core source change, force-recreate the
> downstream containers so they pick up the new binary:
>
> ```bash
> make docker
> docker compose -f packages/meta-gateway/dev/docker-compose.gateway.yml \
> up -d --force-recreate metagateway-hub-metacore
> docker compose -f packages/meta-share/dev/docker-compose.yml \
> --profile share-10node up -d --force-recreate metashare-core metashare-core-test
> docker compose -f packages/meta-read/dev/docker-compose.yml \
> up -d --force-recreate metaread-dev-core
> docker compose -f packages/meta-listen/dev/docker-compose.yml \
> up -d --force-recreate metalisten-dev-core
> ```
>
> The symptom of a missed recreate is missing API fields on `/urls`
> (e.g. `webdavUrlInternal` absent → meta-gateway's
> `store_poster_for_record` silently fails and torznab posters never
> land). Audit recipe:
>
> ```bash
> docker inspect meta-core:local --format '{{.Id}}' # fresh SHA
> docker ps --filter ancestor=meta-core:local --format '{{.Names}}' # repeat for :latest
> # any container whose Image SHA doesn't match the fresh SHA needs --force-recreate.
> ```
### Dev container
In the MetaMesh dev stack, the container is brought up by `dev/docker-compose.yml`:
```bash
cd dev && ./scripts/start.sh
```
The user-facing URL is `https://metacore-dev.localhost:8083`; the direct-backend
HTTP port (no auth, bypasses Caddy) is `http://localhost:18083`.
## Configuration
Environment variables (from `internal/config/config.go` unless noted):
| Variable | Default | Description |
|---|---|---|
| `META_CORE_PATH` | `/meta-core` | meta-core's own volume root (lock, SQLite DB, identity, mounts, watchers, cache). No other service mounts it. |
| `FILES_PATH` | `/files` | Files volume root. |
| `SERVICE_NAME` | `meta-core` | Name in the beacon v2 advertise. |
| `SERVICE_VERSION` | `1.0.0` | Reported via `/status`. |
| `API_PORT` | `8180` | External port baked into the constructed `baseUrl` when `BASE_URL` is unset. |
| `BASE_URL` | _empty_ | Overrides the constructed `baseUrl` (the Caddy/HTTPS perimeter URL). |
| `META_CORE_PUBLIC_URL` | _empty_ | Browser-facing nav URL in the announce; wins over `BASE_URL` (e.g. a debug-direct port with no Caddy). |
| `META_CORE_DB_PATH` | `<META_CORE_PATH>/db/meta-core.db` | SQLite database file. Dev stacks set `/meta-core-db/meta-core.db` on a named volume (the `/meta-core` bind is 9p on Windows dev boxes and SQLite WAL is unsafe there). |
| `META_CORE_DB_CACHE_MB` | `64` | Page cache of the writer connection (`internal/storage/client.go`). |
| `META_CORE_DB_READER_CACHE_MB` | `16` | Page cache per reader connection. |
| `META_CORE_DB_READERS` | `8` | Reader connection pool size. |
| `META_CORE_HTTP_PORT` | `9000` | Go HTTP+SSE+WebDAV port. |
| `META_CORE_HTTP_HOST` | `0.0.0.0` | HTTP bind. |
| `ENABLE_FILE_WATCHER` | `true` | Disable to suppress the in-process watcher entirely (`POST /api/files/register` stays available). |
| `ENABLE_UDP_DISCOVERY` | `true` | beacon v2 advertise + listen. |
| `BEACON_GROUP` / `BEACON_PORT` | `239.255.99.1` / `9099` | Multicast group and UDP port. |
| `BEACON_INTERVAL_MS` | `10000` | Unsolicited advertise interval. |
| `ELECTION_RETRY_SECS` | `5` | flock retry interval (read by `docker/leader-election.sh`, not the Go binary). |
`HEALTH_CHECK_INTERVAL_MS`, `HEARTBEAT_INTERVAL_MS`, `STALE_THRESHOLD_MS`,
`CLEANUP_INTERVAL_MS`, `DEAD_SERVICE_THRESHOLD_MS`, `WATCH_INTERVAL_MS` and
`DEBOUNCE_MS` are still parsed by `internal/config/config.go` but nothing reads
them (leftovers of the file-based registry); setting them has no effect. There
is no `REDIS_PORT` / `META_CORE_REDIS_PORT` / `META_CORE_INDEX_EXCLUDE_PREFIXES`
(gone with Redis and the in-memory search index; search results now include
`categories/newznab/*` like every record read) / `META_CORE_SERVICE_NAME` /
`META_CORE_LEADER_TIMEOUT`, and no `WATCH_PATHS` — watched folders are watcher
configs created via `/api/watchers`.
## API reference
All endpoints below are registered in `internal/api/server.go` (mounts,
watcher and watchers routes in their own packages' `handlers.go`). Examples assume
the in-container Go port `:9000`; from the host use
`https://metacore-dev.localhost:8083` (Caddy) or `http://localhost:18083`
(debug-direct).
### Health, leader, URLs
```bash
GET /health # storage + role (`redis: bool` kept for compatibility = store open)
GET /status # version, uptime, etc.
GET /leader # current leader info (hostname, PID, timestamps)
GET /urls # baseUrl, apiUrl, webdavUrl, webdavUrlInternal (redisUrl is always "", kept for compatibility)
GET /neighbors # neighbours heard over UDP (beacon v2)
GET /api/neighbors # same, under /api
GET /api/stats # dashboard counters (see below)
```
`/services`, `/api/services`, `/services/{name}` and `/services/cleanup/stats`
are **gone** — the registration-and-heartbeat registry they served was replaced
by beacon v2 (`/neighbors`). nginx answers an unknown non-`/api` path
with the dashboard's `index.html`, so a stale caller gets `200 text/html` rather
than a 404; that is what made the dashboard fail with
`SyntaxError: Unexpected token '<'` until 1.0.21.
#### `GET /api/stats`
Every headline counter in one request, split by cost:
```jsonc
{
"records": 88709, // count of idx:roots/* — metadata roots, file or not
"redisKeys": 3115447, // kv row count (name kept for compatibility; cached 60 s)
"redisMemory": "588.74M",// DB + WAL file size (name kept for compatibility)
"identities": 3, // signing accounts on disk
"files": { "count": 4864, "totalSize": 64587914424 }, // null until first sweep
"udlUsers": 5, // accounts holding User Data Layer records
"sweptAt": 1789402401970,
"sweeping": false
}
```
`records` and `identities` are live on every call; `redisKeys` is cached 60 s. `files` and
`udlUsers` need a keyspace walk (~0.5s and ~3s respectively on an 88k-record
box), so they are served from a single-flight cache refreshed in the background
with a 60s TTL — the walk is **never** on the request path, because the
dashboard polls and ten open tabs must not cost ten keyspace walks. Prefer this
over `/api/kv/info`, which does one `GET` per root (6s+) and sums `sizeByte`
across records that share a file.
### Metadata — primary surface
These are the routes other services use. `{hash}` may be a UUID root or
any registered CID alias; CID aliases resolve to the underlying UUID
before reads/writes (`internal/storage/cid_resolution.go`).
```bash
GET /meta # list of root IDs
GET /meta/{hash} # full document (flat keys → nested JSON)
PUT /meta/{hash} # replace document
PATCH /meta/{hash} # merge into document
DELETE /meta/{hash} # delete root + all CID aliases
GET /meta/{hash}/{key...} # single property (key may contain "/")
PUT /meta/{hash}/{key...} # set single property
DELETE /meta/{hash}/{key...} # delete single property
POST /meta/{hash}/_add/{key...} # add value to set-valued property
```
CID-addressed access (public; auth-bypassed in the Caddy perimeter):
```bash
GET /api/meta/{cid} # resolve CID → metadata document
GET /api/file/{cid}/info # CID resolution metadata
GET /file/{cid} # serve file bytes (range-aware)
POST /file/cid # compute CID for an uploaded file
POST /api/files/register # mint + alias one file under /files/plugin by midhash
# (the watcher's path for one file; works with the watcher OFF)
HEAD /data/{hash} # existence + size
GET /data/{hash}/path # absolute path on /files
```
(There is no `/data/{hash}/stream`; bulk reads go through `/webdav/*` or
the `/file/{cid}` reverse-lookup path.)
### Editor / KV browser surface
```bash
GET /api/metadata/hash-ids
GET /api/files/tuples
GET /api/metadata/list
POST /api/metadata/search
POST /api/metadata/batch
POST /api/metadata/clear
GET /api/metadata/{hashId}
PUT /api/metadata/{hashId}
DELETE /api/metadata/{hashId}
GET /api/metadata/{hashId}/property
PUT /api/metadata/{hashId}/property
GET /api/kv/info
GET /api/kv/keys
GET /api/kv/tree # cursor is an opaque next-key ("0" when exhausted)
GET /api/kv/search
GET /api/kv/find
GET /api/kv/value # type is always "string" for an existing key
PUT /api/kv/value
DELETE /api/kv/value
GET /api/kv/key/{key...}
GET /api/schema
POST /api/schema/rescan
GET /api/snapshot/export
POST /api/snapshot/import
POST /api/snapshot/wipe
```
### SSE event streams
The HTTP-mirror of the store's event streams (Redis Streams until 2026-10;
IDs keep the `<ms>-<seq>` form). External services never read the store
directly — they subscribe here with `Last-Event-ID` for resume. See
[`docs/api-mediated-access.md`](docs/api-mediated-access.md) for the wire
contract (one event per stream entry, opaque IDs, heartbeats, gap
signalling).
```bash
GET /api/events/files # file:events stream (watcher events)
GET /api/events/meta # meta:events stream (metadata mutations)
GET /api/events/poll # DEPRECATED long-poll over file:events — use SSE
```
### Identity (signing keystore)
Reached through meta-search's identity proxy (and directly by meta-gateway,
meta-read, meta-listen) for record signing, UDL writes and keypair sign-in.
```bash
GET /api/identity # status (never the private key)
GET /api/identity/accounts
POST /api/identity/generate # the only call that returns a new private key
POST /api/identity/import
POST /api/identity/challenge # one-shot challenge for proof-of-possession
POST /api/identity/reveal # needs proof-of-possession
DELETE /api/identity # needs proof-of-possession; reports purged UDL counts
POST /api/identity/sign
POST /api/identity/sign-batch
GET /api/identity/aead-key
```
### User Data Layer
Records arrive signed (private-tier ones encrypted) as opaque base64 CBOR;
writes are version-gated (stale → `409 stale_version`, or `accepted:false` per
cell in a batch). Storage model in `internal/storage/udl.go` (`udl:rec:<uid>/<cid>/<key>` → JSON `{record,version,ts,value?}`; index sets as one key per member).
```bash
GET /api/udl/record?uid&cid&key
PUT /api/udl/record
PUT /api/udl/records # batch
GET /api/udl/user/{uid}/key/{key}
GET /api/udl/user/{uid}/cid/{cid}
GET /api/udl/user/{uid}/all
GET /api/udl/user/{uid}/count
GET /api/udl/cid/{cid}/users
GET /api/udl/cid/{cid}/aggregate # meta-watch Aggregate wire shape
GET /api/udl/users/stats
```
### Mounts
```bash
GET /api/mounts
POST /api/mounts
GET /api/mounts/{id}
PUT /api/mounts/{id} # also PATCH
DELETE /api/mounts/{id}
POST /api/mounts/{id}/mount
POST /api/mounts/{id}/unmount
POST /api/mounts/{id}/safe-unmount
POST /api/mounts/{id}/scan
GET /api/mounts/rclone/remotes
```
### Watchers
```bash
GET /api/watchers
POST /api/watchers
GET /api/watchers/{id}
PUT /api/watchers/{id}
DELETE /api/watchers/{id}
POST /api/watchers/{id}/scan
POST /api/watchers/{id}/reset
POST /api/watchers/scan-all
POST /api/watchers/reset-all
```
The legacy `/api/scan/trigger` and `/api/scan/status` still respond but
return a deprecation pointer at the `/api/watchers/*` routes
(`internal/watcher/handlers.go:32-33`).
### WebDAV
```bash
GET/PUT/DELETE /webdav/... # mounted on /files
```
The one-shot Redis-era admin migrations (`/api/admin/migrate-dual-roots`,
`migrate-domain-screen`, `migrate-user-cids`, `sweep-literature-echoes`) were
removed with the 2026-10 SQLite switch; they had been run once on
watch.nsl.sh before the migration.
No `/metrics` endpoint is exposed; observability is via container logs and
the `/health` / `/status` JSON.
## DB-file mutex
`docker/leader-election.sh` is a bash flock loop, not a Go-level state
machine. When `flock` succeeds on `/meta-core/locks/kv-leader.lock`, the
script `exec`s supervisord; a second container mounting the same volume
retries every `ELECTION_RETRY_SECS` and stays dormant. When the process tree
dies, the kernel releases the lock. There is no follower path inside the Go
binary.
The lock is a **mutex, not service discovery** — it only stops two
writers landing on one database file (`db/meta-core.db`). Nothing reads it, and the `kv-leader.info`
file it used to publish is gone: siblings locate meta-core over UDP
(see [beacon-v2.md](../../docs/project-architecture/beacon-v2.md)).
`internal/leader` keeps its name for history, but only builds the `/urls`
payload (`baseUrl`, `apiUrl`, `webdavUrl`, `webdavUrlInternal`) that `/urls`
and the UDP announce share.
## Metadata storage shape (one-line summary)
Roots are opaque UUIDv7 strings; every property is a separate row
of the `kv` table at `file:<uuid>/<property>`; every known CID is a key-set member
`file:<uuid>/cids/<bareCid>` plus a reverse-index entry `cid:<bareCid> → <uuid>`
(the canonical CID is derived by rank on read, never stored). Full details in
[`docs/metadata-storage-structure.md`](docs/metadata-storage-structure.md)
and design rationale in [`docs/uuid-rooted-metadata.md`](docs/uuid-rooted-metadata.md).
The authoritative registry of field semantics and value formats lives in
the repo-root [`METADATA_KEYS.md`](../../METADATA_KEYS.md).
## Internal packages
| Package | Purpose |
|---------|---------|
| `cmd/meta-core` | Entry point; store open + schema sentinel + UDP discovery + service wiring. |
| `internal/config` | Env-driven configuration, path helpers. |
| `internal/leader` | `LeaderInfoProvider` — builds the `/urls` payload from hostname/IP/config; no election logic. |
| `internal/meshdisco` | beacon v2 node (advertise, probe, neighbour map) — the Go port of the spec. |
| `internal/kv` | Storage engine: SQLite `kv` table, single writer + group commit, reader pool, in-transaction change events (`kv.go`), event streams as rows (`stream.go`). |
| `internal/storage` | Flat-key records (`client.go`), UUIDv7 minting, CID reverse index (`cid_resolution.go`), schema sentinel, search over `kv_field` + FTS (`search.go`), UDL store (`udl.go`, `udl_admin.go`), stats. |
| `internal/cid` | CID parsing + rank ladder for canonical-CID selection (`cid-rank-vectors.json`, guarded by the meta-root `scripts/check-cid-vectors.sh`). |
| `internal/identity` | Multi-account secp256k1 keystore, challenge/proof-of-possession, signature verification. |
| `internal/api` | HTTP server + all handlers + SSE event endpoints + search matchers + `/api/stats`. |
| `internal/schema` | Per-field schema, folded from counters the write path keeps exact (`idx:schema/…`). |
| `internal/snapshot` | Snapshot export / import / wipe. |
| `internal/watcher` | File system scanner, MidHash256 computation, dispatcher, state registry. |
| `internal/watchers` | Polling-based watcher configurations (manager + poller + handlers). |
| `internal/mounts` | rclone mount manager, lifecycle handlers, stats poller. |
| `internal/webdav` | WebDAV handler (mounted at `/webdav/*`; nginx handles caching upstream). |
### Startup sequence
```
1. Load configuration from environment
2. Build LeaderInfoProvider (no election — the bash gate already won)
3. Open the SQLite store (META_CORE_DB_PATH or /meta-core/db/meta-core.db)
4. EnsureSchemaVersion — abort if the existing store layout is stale
5. Start beacon v2 node (unless ENABLE_UDP_DISCOVERY=false)
6. Construct API server (identity keystore migration, watcher, watchers,
mounts, WebDAV)
7. EnsureCounters — one-time build of the derived counters (record count,
per-field schema) on a store that predates them; blocking, ~1 min at 169k
records, then never again
8. Start API server + pollers (no republish: consumers that want the whole
state ask /api/events/meta for `0-0` and get a snapshot)
9. Wait for SIGINT/SIGTERM, shutdown in reverse order
```
## Dependencies
| Dependency | Purpose |
|------------|---------|
| `github.com/gorilla/mux` | HTTP router |
| `modernc.org/sqlite` | Embedded SQLite (pure Go, CGO off) |
| `github.com/google/uuid` | UUIDv7 minting |
| `github.com/decred/dcrd/dcrec/secp256k1/v4`, `golang.org/x/crypto`, `github.com/mr-tron/base58` | Identity keys, signing, AEAD key derivation |
| `golang.org/x/net` | WebDAV support |
Runtime requirements: Go 1.21+ at build time; the container ships
rclone, nginx, and supervisord alongside the binary, plus the React dashboard
and metadata editor (built from `dashboard/` and `editor/` in the Dockerfile).
## License
Part of the MetaMesh project.
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