> ## Documentation Index
> Fetch the complete documentation index at: https://filament.getgalaxy.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Writing a Source

> The Source interface and how to implement it.

A source implements `Source`, defined in the repo's root `source.go`:

```go theme={"theme":"vitesse-black"}
type Source interface {
	Spec() ConnectorSpec
	Validate(cfg Config) error
	Configure(ctx context.Context, cfg Config) error
	Extract(ctx context.Context, sink RecordSink, opts ExtractOpts) error
	Teardown(ctx context.Context) error
}
```

* **`Spec`** is the connector's self-description — identity, supported
  [replication modes](/pages/guides/concepts/replication-modes), config schema, and
  resource capabilities. It's what powers the catalog (see [Connectors
  overview](/pages/connectors/overview/introduction)).
* **`Validate`** and **`Configure`** check and apply a `Config` before any
  extraction runs.
* **`Extract`** reads into a `RecordSink` under the given `ExtractOpts`
  (which resources, which mode, how fast).
* **`Teardown`** releases whatever `Configure` acquired.

## Describing your config

`ConnectorSpec.Config` is a `ConfigSchema` — a list of `ConfigField`s, each
with a type (`FieldString`, `FieldSecret`, `FieldEnum`, `FieldObject`, …), a
scope (`ScopeConnection` for fields reusable across runs, like a DSN;
`ScopePipeline` for fields that vary per pipeline, like a table name), and
optionally a `VisibleWhen` condition for conditional fields in the UI.

## Optional capabilities

A source can implement none, some, or all of several optional interfaces —
resumable extraction, CDC, resource discovery, rate limiting, and more. See
[Optional interfaces](/pages/connectors/building-a-connector/optional-interfaces).

## Registering it

Add a `register.go` that registers your source with the engine, then blank-import
the package wherever it should be available — see [Embedding as a
library](/pages/guides/deployment/embedding-as-a-library).