Configuration

The options you pass when opening a database, and the barrel_server app environment.

This lists the knobs you set when you open a database, and the settings the server reads from its app environment. Use it as a lookup; the guides explain when you would change each one.

Opening a database

barrel:open/2 takes options per layer:

{ok, Db} = barrel:open(mydb, #{
    vectordb => #{
        dimension => 768,        %% embedding dimension
        bm25_backend => memory   %% none (default) | memory | disk
    },
    embedding => #{provider => openai},   %% record mode: auto-embed on write
    encryption => default                 %% encrypt at rest with a provided key
}).

Layer / key	Meaning
`vectordb.dimension`	Vector dimension (default 768).
`vectordb.bm25_backend`	Keyword index: `none`, `memory`, or `disk`.
`vectordb.hnsw_m`, `hnsw_ef_construction`, `hnsw_ef_search`	HNSW index tuning.
`embedding`	An embedding policy so documents auto-embed. See Record mode.
`encryption`	`disabled` (default), `default`, or a provider spec. See Encryption.

Server configuration

barrel_server reads its settings from the barrel_server app environment (sys.config):

{barrel_server, [
    {http_port, 8080},
    {data_dir, "data"},
    {cors, #{origins => [<<"https://app.example">>]}},
    {auth, #{tokens => [<<"...">>]}},
    {mcp, #{enabled => true}}
]}.

Key	Meaning
`http_port`	Listen port (default 8080).
`data_dir`	Where databases are stored.
`dbs_idle_timeout`, `dbs_max_open`	The lifecycle manager: idle close and the open-handle LRU.
`cors`	Allowed origins for browser clients (needed by barrel-lite).
`auth`	Server bearer tokens; capability tokens are issued per space.
`mcp`	The MCP endpoint: `enabled`, `resources`, `live`.

See Running the server for the full picture.