README.md

# Snap

[![Hex pm](http://img.shields.io/hexpm/v/snap.svg?style=flat)](https://hex.pm/packages/snap)

Snap is an Elasticsearch client. It provides a flexible, performant API on
top of your Elasticsearch cluster, supporting high level features like
versioned index management, while also providing a convenient interface into
low level operations.

See the full [API docs](https://hexdocs.pm/snap).

## Features

- Versioned index management with zero-downtime hotswapping (compatible with [`elasticsearch`](https://github.com/danielberkompas/elasticsearch-elixir))
- Streaming bulk operations
- Connection pooling
- Telemetry events
- High level interface over the [Multi Search API](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-multi-search.html)

## Installation

The package can be installed by adding `snap` to your list of dependencies in
`mix.exs`:

```elixir
def deps do
  [
    {:snap, "~> 0.9"},
    {:finch, "~> 0.16"}, # By default, Snap uses Finch to make HTTP requests
  ]
end
```

Snap supports Elixir 1.12 or later.

## Usage

Implement your own cluster module, similar to an `Ecto.Repo`:

```elixir
defmodule MyApp.Cluster do
  use Snap.Cluster, otp_app: :my_app
end
```

Configure it:

```elixir
config :my_app, MyApp.Cluster,
  url: "http://localhost:9200",
  username: "my_username",
  password: "my_password"
```

Then wire it into your application supervisor:

```elixir
def start(_type, _args) do
  children = [
    {MyApp.Cluster, []}
  ]

  opts = [strategy: :one_for_one, name: MyApp.Supervisor]
  Supervisor.start_link(children, opts)
end
```

Now you can perform operations on your cluster:

```elixir
{:ok, %{"count" => count}} = MyApp.Cluster.get("/my-index/_count")
```

## Testing

If you want to test your app that uses this library, but don't want to have integration tests
with a Elasticsearch instance running in you local dev environment,
you can mock the responses using a custom HTTP client adapter.

Supposing you are using [mox](https://github.com/dashbitco/mox), you can do something like this:

```elixir
# in test_helper.exs
Mox.defmock(HTTPClientMock, for: Snap.HTTPClient)
Mox.stub(HTTPClientMock, :child_spec, fn _config -> :skip end)

# in config/test.exs
config :my_app, MyApp.Cluster, http_client_adapter: HTTPClientMock

# in a test file
Mox.expect(HTTPClientMock, :request, fn _cluster, _method, _url, _headers, _body, _opts
  body = "{}" # valid json
  {:ok, %Snap.HTTPClient.Response{status: 200, headers: [], body: body}}
end)
```

See the [API documentation](https://hexdocs.pm/snap) for more advanced features.