# Batch
[](https://travis-ci.org/fertapric/batch)
Batches are processes meant to execute several functions asynchronously, collecting
their return values or returning the error of the first failure (fail-fast).
## Installation
Add `batch` to your project's dependencies in `mix.exs`:
```elixir
def deps do
[{:batch, "~> 0.2"}]
end
```
And fetch your project's dependencies:
```shell
$ mix deps.get
```
## Usage
Let's start with an example:
```elixir
batch = Batch.async([
fn -> Blog.get_post(post_id) end,
fn -> Blog.get_comments(post_id) end
])
{:ok, [post, comments]} = Batch.await(batch)
```
As shown in the example above, batches spawned with `async` can be awaited on by their caller process (and only their caller). They are implemented by spawning a process that sends a message to the caller once the given computation is performed. Internally, the batch process spawns a new process per function (linked and monitored by the batch process) and awaits for replies.
Successful computations are represented with the `:ok` atom or the `{:ok, result}` tuple.
```elixir
batch = Batch.async([
fn -> {:ok, 1 + 1} end,
fn -> :ok end,
{Enum, :fetch, [[2, 4, 6], 1]}
])
{:ok, [{:ok, 2}, :ok, {:ok, 4}]} = Batch.await(batch)
```
Any other value will be considered a failure. Failures and exits are reported immediately (fail-fast), shutting down all the processes.
```elixir
batch = Batch.async([
fn -> {:ok, 1 + 1} end,
fn -> {:ok, 2 + 2} end,
fn -> :error end
])
{:error, :error} = Batch.await(batch)
```
Batches can also be started as part of a supervision tree and dynamically spawned on remote nodes. We will explore all three scenarios next. [Check the documentation](https://hexdocs.pm/batch) for more information.
## Documentation
Documentation is available at https://hexdocs.pm/batch
## Contributing
Bug reports and pull requests are welcome on GitHub at https://github.com/fertapric/batch. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the [Contributor Covenant](http://contributor-covenant.org) code of conduct.
### Running tests
Clone the repo and fetch its dependencies:
```shell
$ git clone https://github.com/fertapric/batch.git
$ cd batch
$ mix deps.get
$ mix test
```
### Building docs
```shell
$ mix docs
```
## Copyright and License
Copyright 2017 Fernando Tapia Rico
Batch source code is licensed under the [MIT License](LICENSE).
