# Xandra
[](https://travis-ci.org/lexhide/xandra)
[](https://hex.pm/packages/xandra)
> Fast, simple, and robust Cassandra driver for Elixir.
Xandra is a [Cassandra][cassandra] driver built natively in Elixir and focused on speed, simplicity, and robustness.
## Features
This library is in its early stages when it comes to features, but we're already [successfully using it in production at Football Addicts][production-use]. Currently, the supported features are:
* performing queries (including parameterized queries) on the Cassandra database
* connection pooling
* reconnections in case of connection loss
* prepared queries (including a local cache of prepared queries on a per-connection basis)
* batch queries
* page streaming
* compression
* clustering (random and priority load balancing for now)
* customizable retry strategies for failed queries
* user-defined types
* authentication
In the future, we plan to add more features, like more load balancing strategies for clustering. See [the documentation][documentation] for detailed explanation of how the supported features work.
## Installation
Add the `:xandra` dependency to your `mix.exs` file:
```elixir
def deps() do
[{:xandra, ">= 0.0.0"}]
end
```
and add `:xandra` to your list of applications:
```elixir
def application() do
[applications: [:logger, :xandra]]
end
```
Then, run `mix deps.get` in your shell to fetch the new dependency.
## Overview
The documentation is available [on HexDocs][documentation].
Connections or pool of connections can be started with `Xandra.start_link/1`:
```elixir
{:ok, conn} = Xandra.start_link(host: "127.0.0.1", port: 9042)
```
This connection can be used to perform all operations against the Cassandra server.
Executing simple queries looks like this:
```elixir
statement = "INSERT INTO users (name, postcode) VALUES ('Priam', 67100)"
{:ok, %Xandra.Void{}} = Xandra.execute(conn, statement, _params = [])
```
Preparing and executing a query:
```elixir
with {:ok, prepared} <- Xandra.prepare(conn, "SELECT * FROM users WHERE name = ?"),
{:ok, %Xandra.Page{}} <- Xandra.execute(conn, prepared, [_name = "Priam"]),
do: Enum.to_list(page)
```
Xandra supports streaming pages:
```elixir
prepared = Xandra.prepare!(conn, "SELECT * FROM subscriptions WHERE topic = :topic")
page_stream = Xandra.stream_pages!(conn, prepared, _params = [], page_size: 1_000)
# This is going to execute the prepared query every time a new page is needed:
page_stream
|> Enum.take(10)
|> Enum.each(fn(page) -> IO.puts "Got a bunch of rows: #{inspect(Enum.to_list(page))}" end)
```
## Contributing
Clone the repository and run `$ mix test` to make sure your setup is correct; you're going to need Cassandra running locally on its default port (`9042`) for tests to pass.
## License
Xandra is released under the ISC license, see the [LICENSE](LICENSE) file.
[documentation]: https://hexdocs.pm/xandra
[cassandra]: http://cassandra.apache.org
[production-use]: http://tech.footballaddicts.com/blog/the-pursuit-of-instant-pushes
