Barrel is an embeddable edge-AI database for Erlang: documents, their attachments (blobs), and their vectors under one id, with local vector and keyword search, encryption at rest, branching/PITR, replication, and an agent layer. This umbrella groups the applications so they develop and release together, while each stays a standalone OTP application with its own public API.
| App | Path | Responsibility |
|---|---|---|
barrel |
apps/barrel |
The embeddable database. Composes docdb + vectordb + crypto so a document, its blobs, and its vector share one id. Record mode, timeline (branch/PITR/merge), BQL, the database lifecycle manager, and contexts (federated queries over local and remote databases, working sets, export and read-only import). Serves no network protocol. |
barrel_docdb |
apps/barrel_docdb |
The document layer. HLC version-vector MVCC, changes feed, replication, attachments (blobs), TTL, retained history, BQL query. Standalone embedded document database. |
barrel_ngram |
apps/barrel_ngram |
Exact substring and regex search over a barrel_docdb database via a byte-level trigram index with checksummed segments. |
barrel_vectordb |
apps/barrel_vectordb |
The vector layer. Local ANN indexes (HNSW, DiskANN, FAISS), BM25, hybrid search, quantization. Standalone embedded vector database. |
barrel_embed |
apps/barrel_embed |
Embedding generation across providers (local Python, Ollama, OpenAI, and more). Used by barrel_vectordb for text and hybrid search. |
barrel_rerank |
apps/barrel_rerank |
Cross-encoder reranking. Optional, used by barrel_vectordb. |
barrel_crypto |
apps/barrel_crypto |
Encryption-at-rest primitives: AES-256-GCM envelope, offset-addressable CTR, HKDF key derivation, key providers. |
barrel_spaces |
apps/barrel_spaces |
The agent layer: spaces (shared context databases), capability tokens, sessions with TTL, and handoffs. |
barrel_server |
apps/barrel_server |
The network server. Exposes barrel over HTTP (REST/JSON) and MCP using livery, contexts and working sets included. Opt-in behind the server profile. |
barrel_att_s3 |
apps/barrel_att_s3 |
S3-compatible attachment backend for barrel_docdb. Opt-in behind the s3 profile. |
barrel_faiss |
apps/barrel_faiss |
Erlang NIF bindings for FAISS. Optional; needs the FAISS C++ library, so it is excluded from the default build. |
Dependency direction (no cycles): barrel_server -> {barrel, barrel_spaces,
barrel_ngram}; barrel_spaces -> {barrel, barrel_docdb, barrel_crypto};
barrel -> {barrel_docdb, barrel_vectordb, barrel_crypto}; barrel_vectordb
-> {barrel_embed, barrel_crypto} (optionally barrel_faiss, barrel_rerank);
barrel_ngram -> barrel_docdb; barrel_att_s3 -> barrel_docdb;
barrel_docdb -> barrel_crypto. Leaves:
barrel_crypto, barrel_embed, barrel_rerank, barrel_faiss.
You need Erlang/OTP, rebar3, CMake, and a C/C++ compiler (the barrel_vectordb
NIF is built with CMake).
rebar3 compile
This builds the default app set (barrel_crypto, barrel_docdb,
barrel_ngram, barrel_vectordb, barrel_embed, barrel_rerank, barrel,
barrel_spaces). barrel_faiss, barrel_server and barrel_att_s3 are
opt-in:
rebar3 as faiss compile # add the FAISS NIF app
rebar3 as server compile # add the HTTP/MCP server
rebar3 as s3 compile # add the S3 attachment backend
rebar3 eunit # unit tests
rebar3 ct # Common Test suites
rebar3 as server ct # the HTTP/MCP server (opt-in profile)
rebar3 shell # starts the embeddable stack
rebar3 as server shell # starts barrel_server
Each application stays a valid OTP application usable on its own. You can embed
barrel (the full database) directly with no transports, or use barrel_docdb and
barrel_vectordb as standalone embedded databases, without a server, remote
replication, or any cluster fabric.
- Docs index: docs/README.md
- Feature status: docs/features.md
- Architecture: docs/architecture/overview.md and docs/architecture/vision.md
- Guides live under docs/guides/; per-app docs under each app.
- Distributing the apps (Hex + git mirrors): docs/guides/distributing-apps.md
Apache-2.0. See the LICENSE file at the repository root and in each app
directory.