ExAws

A flexible easy to use set of AWS APIs.

• ExAws.Dynamo
• ExAws.EC2
• ExAws.Kinesis
• ExAws.Lambda
• ExAws.RDS
• ExAws.S3
• ExAws.SNS
• ExAws.SQS

1.0.0-beta0 Changes

The v0.5 branch holds the legacy approach.

ExAws 1.0.0 takes a more data driven approach to querying APIs. The various functions that exist inside a service like S3.list_objects or Dynamo.create_table all return a struct which holds the information necessary to make that particular operation.

You then have 4 ways you can choose to execute that operation:

# Normal
S3.list_buckets |> ExAws.request #=> {:ok, response}
# With per request configuration overrides
S3.list_buckets |> ExAws.request(config) #=> {:ok, response}

# Raise on error, return successful responses directly
S3.list_buckets |> ExAws.request! #=> response
S3.list_buckets |> ExAws.request!(config) #=> response

Certain operations also support Elixir streams:

S3.list_objects("my-bucket") |> ExAws.stream! #=> #Function<13.52451638/2 in Stream.resource/3>
S3.list_objects("my-bucket") |> ExAws.stream!(config) #=> #Function<13.52451638/2 in Stream.resource/3>

The ability to return a stream is noticed in the function’s documentation.

Migration

TL;DR: Do this now:

ExAws.S3.get_object("my-bucket", "path/to/object") |> ExAws.request

not

ExAws.S3.get_object("my-bucket", "path/to/object")

This change greatly simplifies the ExAws code paths, and removes entirely the complex meta-programming pervasive to the original approach. However, it does constitute a breaking change for anyone who had a client with custom logic.

Highlighted Features

• Easy configuration.
• Minimal dependencies. Choose your favorite JSON codec and HTTP client.
• Elixir streams to automatically retrieve paginated resources.
• Elixir protocols allow easy customization of Dynamo encoding / decoding.
• mix kinesis.tail your-stream-name task for easily watching the contents of a kinesis stream.
• Simple. ExAws aims to provide a clear and consistent elixir wrapping around AWS APIs, not abstract them away entirely. For every action in a given AWS API there is a corresponding function within the appropriate module. Higher level abstractions like the aforementioned streams are in addition to and not instead of basic API calls.

Getting started

Add ex_aws to your mix.exs, along with your json parser and http client of choice. ExAws works out of the box with Poison and HTTPoison and sweet_xml. All APIs require an http client, but only some require a json or xml codec. You only need the codec for the API you intend to use. At this time only SweetXml is supported for xml parsing.

• Dynamo: json
• Kinesis: json
• Lambda: json
• SQS: xml
• S3: xml

If you wish to use instance roles to obtain AWS access keys you will need to add a JSON codec whether the particular API requires one or not.

def deps do
  [
    {:ex_aws, "~> 1.0.0-beta0"},
    {:poison, "~> 2.0"},
    {:httpoison, "~> 0.8"}
  ]
end

Don’t forget to add :httpoison to your applications list if that’s in fact the http client you choose. :ex_aws must always be added to your applications list.

def application do
  [applications: [:ex_aws, :httpoison, :poison]]
end

That’s it!

ExAws has by default the equivalent including the following in your mix.exs

config :ex_aws,
  access_key_id: [{:system, "AWS_ACCESS_KEY_ID"}, :instance_role],
  secret_access_key: [{:system, "AWS_SECRET_ACCESS_KEY"}, :instance_role]

This means it will first look for the AWS standard AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY environment variables, and fall back using instance meta-data if those don’t exist. You should set those environment variables to your credentials, or configure an instance that this library runs on to have an iam role.

Usage

ExAws ships with a default client for each API: [ExAws.Dynamo, ExAws.Kinesis, ExAws.Lambda, ExAws.S3]

For particular usage instructions, please consult the client definition for your desired service.

• ExAws.Dynamo.Client
• ExAws.Kinesis.Client
• ExAws.Lambda.Client
• ExAws.S3.Client

Dynamo usage example:

defmodule User do
  @derive [ExAws.Dynamo.Encodable]
  defstruct [:email, :name, :age, :admin]
end

alias ExAws.Dynamo

# Create a users table with a primary key of email [String]
# and 1 unit of read and write capacity
Dynamo.create_table("Users", "email", %{email: :string}, 1, 1)

user = %User{email: "bubba@foo.com", name: "Bubba", age: 23, admin: false}
# Save the user
Dynamo.put_item("Users", user)

# Retrieve the user by email and decode it as a User struct.
result = Dynamo.get_item!("Users", %{email: user.email})
|> Dynamo.Decoder.decode(as: User)

assert user == result

Consult the relevant documentation for the API of interest.

Supported APIs

• Dynamo
• Kinesis
• Lambda
• SQS
• S3 (in progress)
• Many more planned

Configuration

To configure the built in clients do the following in your config.exs:

config :ex_aws,
  region: "us-east-2",
  dynamodb: [
    region: "us-west-1"
  ]

Top level configuration options (those directly beneath `:ex_aws) will automatically apply to all clients, although a given client can override the default. So for example in the above configuration the first region: "us-east-2" sets the region for dynamo, kinesis, s3 etc to “us-east-2”, but then the particular configuration for dynamo overrides that to “us-west-1”. The following top level configuration options are supported: [:http_client, :json_codec, :access_key_id, :secret_access_key, :debug_requests] ## Client configuration ExAws easily supports more than one client for a given service. To create your own associated with a particular OTP app: ```elixir defmodule MyApp.Dynamo do use ExAws.Dynamo.Client, otp_app: :my_app end

defmodule MyOtherApp.Dynamo do use ExAws.Dynamo.Client, otp_app: :my_other_app end

To configure:

config :my_app, :ex_aws, dynamodb: [] # Dynamo config here

config :my_other_app, :ex_aws, json_codec: ExAws.JSON.JSX # Maybe :my_other_app uses jsx dynamodb: [] # Other Dynamo config here

The association with a particular OTP app is merely for convenience, and is entirely optional. To configure multiple clients without reference to another app simply write your own `config_root/0` in each client to tell ExAws where to find the configuration.

defmodule My.Dynamo do use ExAws.Dynamo.Client

def config_root do

Application.get_all_env(:my_ex_aws)

end end

defmodule MyOther.Dynamo do use ExAws.Dynamo.Client

def config_root do

Application.get_all_env(:my_other_ex_aws)

end end

To configure:

config :my_ex_aws, dynamodb: [] # Dynamo config here

config :my_other_ex_aws, json_codec: ExAws.JSON.JSX # Maybe :my_other_app uses jsx dynamodb: [] # Other Dynamo config here

## ExAws vs. Erlcloud

In addition to its unique features, ExAws has a number of advantages over erlcloud in particular:

- Easier configuration. ExAws uses your normal mix config, erlcloud requires you to separately generate a configuration record.

- Guaranteed configuration. Erlcloud requires you to pass in the configuration with every request as an optional last parameter. If you forget, it will use the default configuration which may have unintended consequences. With ExAws clients you set the configuration once and then never worry about it again.

- Binaries and Maps. ExAws always uses binaries over char lists, and returns maps instead of proplists.

- Few built in dependencies. Already using Poison? No need to add jsx as a dependency.

- Lambda support

It's worth noting however that erlcloud supports a substantially larger set of AWS services at this time.

## License

The MIT License (MIT)

Copyright (c) 2014 CargoSense, Inc.

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The above copyright notice and this permission notice shall be included in
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