# `GeoGenius.Preflight`
[🔗](https://github.com/agoodway/geo_genius/blob/main/lib/geo_genius/preflight.ex#L14)

Verifies GeoGenius's database prerequisites and fails host startup when they
are not met.

Place this child in the host's supervision tree immediately after its Repo:

    children = [
      MyApp.Repo,
      {GeoGenius.Preflight, repo: MyApp.Repo, prefix: "geo_genius"},
      MyAppWeb.Endpoint
    ]

The check runs once during `start_link/1` and returns `:ignore`, so no process
remains in the tree. A failure raises `GeoGenius.PreflightError`, which aborts
startup rather than deferring the error to the first query.

A Repo pooled through `Ecto.Adapters.SQL.Sandbox` skips the check, because
the supervisor starts this child from a process that owns no sandbox
connection: the check would raise `DBConnection.OwnershipError` and take the
host's whole test suite down with it. `guides/installation.md` covers what a
host runs instead under the sandbox.

# `child_spec`

```elixir
@spec child_spec(keyword()) :: Supervisor.child_spec()
```

Builds the child spec for placing this preflight check in a supervision tree.

# `start_link`

```elixir
@spec start_link(keyword()) :: :ignore
```

Runs the preflight check and returns `:ignore` on success.

Raises `GeoGenius.PreflightError` on failure, aborting host startup.

`:enabled?` decides whether the check runs. It defaults to false for a Repo
configured with `Ecto.Adapters.SQL.Sandbox` and true for every other Repo.
Pass it explicitly to override that: `enabled?: true` verifies a sandboxed
Repo from a process that has checked a connection out, `enabled?: false`
skips the check wherever the host prefers to run it by hand.

---

*Consult [api-reference.md](api-reference.md) for complete listing*