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https://github.com/amancevice/yake

A Rake-like DSL for writing AWS Lambda handlers
https://github.com/amancevice/yake

api-gateway aws datadog dsl lambda rake ruby serverless

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A Rake-like DSL for writing AWS Lambda handlers

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# λake

[![gem](https://img.shields.io/gem/v/yake?color=crimson&logo=rubygems&logoColor=eee&style=flat-square)](https://rubygems.org/gems/yake)
[![rspec](https://img.shields.io/github/actions/workflow/status/amancevice/yake/rspec.yml?logo=github&style=flat-square)](https://github.com/amancevice/yake/actions/workflows/rspec.yml)
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[![maintainability](https://img.shields.io/codeclimate/maintainability/amancevice/yake?logo=code-climate&style=flat-square)](https://codeclimate.com/github/amancevice/yake/maintainability)

[![ko-fi](https://ko-fi.com/img/githubbutton_sm.svg)](https://ko-fi.com/smallweirdnumber)

Write your AWS Lambda function handlers using a Rake-like declarative syntax:

```ruby
# ./lambda_function.rb
require 'yake'

handler :lambda_handler do |event|
# Your code here
end

# Handler signature: `lambda_function.lambda_handler`
```

You can even declare Sinatra-like API Gateway routes for a main entrypoint:

```ruby
# ./lambda_function.rb
require 'yake/api'

header 'content-type' => 'application/json'

get '/fizz' do
respond 200, { ok: true }.to_json
end

handler :lambda_handler do |event|
route event
rescue => err
respond 500, { message: err.message }.to_json
end

# Handler signature: `lambda_function.lambda_handler`
```

## Installation

Add this line to your application's Gemfile:

```ruby
gem 'yake'
```

And then execute:

```bash
bundle install
```

Or install it yourself as:

```bash
gem install yake
```

## Why Is It Called "yake"?

"λ" + Rake, but "λ" is hard to type and I think "y" looks like a funny little upside-down-and-backwards Lambda symbol.

## Why Use It?

So why use `yake` for your Lambda functions?

### Event Logging

By default, the `handler` function wraps its block in log lines formatted to match the style of Amazon's native Lambda logs sent to CloudWatch. Each invocation of the handler will log both the _input event_ and the _returned value_, prefixed with the ID of the request:

```plaintext
START RequestId: 149c500f-028a-4b57-8977-0ef568cf8caf Version: $LATEST
INFO RequestId: 149c500f-028a-4b57-8977-0ef568cf8caf EVENT { … }

INFO RequestId: 149c500f-028a-4b57-8977-0ef568cf8caf RETURN { … }
END RequestId: 149c500f-028a-4b57-8977-0ef568cf8caf
REPORT RequestId: 149c500f-028a-4b57-8977-0ef568cf8caf Duration: 43.97 ms Billed Duration: 44 ms Memory Size: 128 MB Max Memory Used: 77 MB
```

Logging the request ID in this way makes gathering logs lines for a particular execution in CloudWatch much easier.

You can customize or disable the logger:

```ruby
logging :off # disables logging entirely
logging pretty: false # Logs event/result in compact JSON
logging :on, MyLogger.new # Use a custom logger
```

Include `Yake::Logger` on a class to access this logger:

```ruby
class Fizz
include Yake::Logger
end

Fizz.new.logger == Yake.logger
# => true
```

### API Routes

A common use of Lambda functions is as a proxy for API Gateway. Oftentimes users will deploy a single Lambda function to handle all requests coming from API Gateway.

Requiring the `yake/api` module will add the API-specific DSL into your handler.

Define API routes using Sinatra-like syntax

```ruby
any '/…' do |event|
# Handle 'ANY /…' route key events
end

delete '/…' do |event|
# Handle 'DELETE /…' route key events
end

get '/…' do |event|
# Handle 'GET /…' route key events
end

head '/…' do |event|
# Handle 'HEAD /…' route key events
end

options '/…' do |event|
# Handle 'OPTIONS /…' route key events
end

patch '/…' do |event|
# Handle 'PATCH /…' route key events
end

post '/…' do |event|
# Handle 'POST /…' route key events
end

put '/…' do |event|
# Handle 'PUT /…' route key events
end
```

Helper methods are also made available to help produce a response for API Gateway:

Set a default header for ALL responses:

```ruby
header 'content-type' => 'application/json; charset=utf-8'
header 'x-custom-header' => 'fizz'
```

Produce an API Gateway-style response object:

```ruby
respond 200, { ok: true }.to_json, 'x-extra-header' => 'buzz'
# {
# "statusCode" => 200,
# "body" => '{"ok":true}',
# "headers" => { "x-extra-header" => "buzz" }
# }
```

Route an event to one of the declared routes:

```ruby
handler :lambda_handler do |event|
route event
rescue Yake::Errors::UndeclaredRoute => err
respond 404, { message: err.message }.to_json
rescue => err
respond 500, { message: err.message }.to_json
end
```

### Zero Dependencies

Finally, `yake` does not depend on any other gems, using the Ruby stdlib only. This helps keep your Lambda packages slim & speedy.

## Support Helpers

As of `~> 0.5`, `yake` comes with a support module for common transformations.

Enable the helpers by requiring the `support` submodule:

```ruby
require 'yake/support'
```

`Object` helpers:

```ruby
MyObject.new.some_method
# => NoMethodError

MyObject.new.try(:some_method)
# => nil

10.try(:some_method) { |x| x ** 2 }
# => 100
```

`Hash` helpers:

```ruby
{ a: { b: 'c', d: 'e' }, f: 'g' }.deep_keys
# => [:a, :b, :d, :f]

left = { a: 'b', c: { d: %w[e] } }
right = { a: 'a', c: { d: %w[d] } }
left.deep_merge(right)
# => { :a => "a", :c => { :d => ["e", "d"] } }

{ a: { b: 'c', d: 'e' }, f: 'g' }.deep_transform_keys(&:to_s)
# => { "a" => { "b" => "c", "d" => "e" }, "f" => "g" }

hash = { a: { b: 'c', d: 'e' }, f: 'g' }
hash.deep_transform_keys!(&:to_s)
# => { "a" => { "b" => "c", "d" => "e" }, "f" => "g" }

{ f: 'g', a: { d: 'e', b: 'c' } }.deep_sort
# => { a: { b: 'c', d: 'e' }, f: 'g' }

{ fizz: 'buzz' }.encode64
# => "eyJmaXp6IjoiYnV6eiJ9\n"

{ fizz: 'buzz', jazz: 'fuzz' }.except(:buzz)
# => { :fizz => 'buzz' }

{ fizz: 'buzz' }.strict_encode64
# => "eyJmaXp6IjoiYnV6eiJ9"

{ fizz: { buzz: %w[jazz fuzz] } }.stringify_names
# => { "fizz" => { "buzz" => ["jazz", "fuzz"] } }

{ 'fizz' => { 'buzz' => %w[jazz fuzz] } }.symbolize_names
# => { :fizz => { :buzz => ["jazz", "fuzz"] } }

{ fizz: 'buzz' }.to_form
# => "fizz=buzz"

{ f: 'g', a: { d: 'e', b: 'c' } }.to_json_sorted
# => '{"a":{"b":"c","d":"e"},"f":"g"}'

{ f: 'g', a: { d: 'e', b: 'c' } }.to_struct
# => #"e", :b=>"c"}>

{ f: 'g', a: { d: 'e', b: 'c' } }.to_deep_struct
# => #>

{ a: { b: 'c', d: 'e' }, f: 'g' }.to_dynamodb
# => { :a => { :M => { :b => { :S => "c" }, :d => { :S => "e" } } }, :f => { :S => "g" } }

{ a: { M: { b: { S: 'c' }, d: { S: 'e' } } }, f: { S: 'g' } }.to_h_from_dynamodb
# => { :a => { :b => "c", :d => "e" }, :f => "g" }
```

`Integer` helpers:

```ruby
7.weeks
# => 4_233_600

7.days
# => 604_800

7.hours
# => 25_200

7.minutes
# => 420

1234567890.utc
# => 2009-02-13 23:31:30 UTC
```

`String` helpers:

```ruby
host = 'https://example.com/'
path = '/path/to/resource'
host / path
# => "https://example.com/path/to/resource"

'snake_case_string'.camel_case
# => "SnakeCaseString"

"Zml6eg==\n".decode64
# => "fizz"

'fizz'.encode64
# => "Zml6eg==\n"

'fizz'.md5sum
# => "b6bfa6c318811be022d4f73070597660"

'fizz'.sha1sum
# => "c25f5985f2ab63baeb2408a2d7dbc79d8f29d02f"

'CamelCaseString'.snake_case
# => "camel_case_string"

'Zml6eg=='.strict_decode64
# => "fizz"

'fizz'.strict_encode64
# => "Zml6eg=="

'{"fizz":"buzz"}'.to_h_from_json
# => { "fizz" => "buzz" }

'fizz=buzz'.to_h_from_form
# => { "fizz" => "buzz" }

'2009-02-13T23:31:30Z'.utc
# => 2009-02-13 23:31:30 UTC
```

`Symbol` helpers

```ruby
:snake_case_symbol.camel_case
# => :SnakeCaseSymbol

:CamelCaseSymbol.snake_case
# => :camel_case_symbol
```

`UTC` Time helpers

```ruby
UTC.at 1234567890
# => 2009-02-13 23:31:30 UTC

UTC.now
# => 2022-02-26 13:57:07.860539 UTC
```

## Datadog Integration

As of `v1.0`, `yake` comes with a helper for writing Lambdas that integrate with Datadog's `datadog-lambda` gem.

As of `~> 0.8`, `yake` uses the v2 Datadog Lambda gem.

Creating a Lambda handler that wraps the Datadog tooling is easy:

```ruby
require 'aws-sdk-someservice'
require 'yake/datadog'

# Configure Datadog to use AWS tracing
Datadog::Lambda.configure_apm { |c| c.tracing.instrument :aws }

datadog :handler do |event|
# …
end
```

## Deployment

After writing your Lambda handler code you can deploy it to AWS using any number of tools. I recommend the following tools:

- [Terraform](https://www.terraform.io) — my personal favorite Infrastructure-as-Code tool
- [AWS SAM](https://aws.amazon.com/serverless/sam/) — a great alternative with less configuration than Terraform
- [Serverless](https://www.serverless.com) — Supposedly the most popular option, though I have not used it

## Development

After checking out the repo, run `bundle` to install dependencies. Then, run `rake spec` to run the tests.

## Contributing

Bug reports and pull requests are welcome on GitHub at [amancevice/yake](https://github.com/amancevice/yake).

## License

The gem is available as open source under the terms of the [MIT License](https://opensource.org/licenses/MIT).