Warning

This project is still in very early development stages, but should be complete enough to use in production. that being said, use this at your own risk.

MineTrain

A lightweight and easy to use shard for running crystal in AWS Lambda

MineTrain was heavily influenced by the following projects:

• https://github.com/spinscale/crystal-aws-lambda
• https://github.com/lambci/crambda

Installation

Add MineTrain to your crystal functions shards.yml file

dependencies:
  mine_train:
    github: SteffanPerry/MineTrain
    version: 0.0.2

Usage

Create a method that optionally accepts the mine train event and context types:

require "mine_train"

class CustomClass
  def self.perform(event : MineTrain::Lambda::Event, context : MineTrain::Lambda::Context)
    # Do work...
  end
end

In your entry file, require mine_train and pass a block to the mine_train_run method:

require "mine_train"
require "./custom_class.cr"

mine_train_run do |event, context|
  CustomClass.perform(event, context)
end

You can use use event values within the mine_train_run block to dynamically call specific jobs based on input. Additionally, methods do not need to accept event or context arguments if they are not required.

# custom_class.cr
require "mine_train"

class CustomClass
  def self.perform(event : MineTrain::Lambda::Event, context : MineTrain::Lambda::Context)
    # Do work...
  end

  def self.perform_two(event : MineTrain::Lambda::Event)
    # Do work...
  end

  def self.perform_three
    # Do work...
  end
end

# main.cr
require "mine_train"
require "./custom_class.cr"

mine_train_run do |event, context|
  case event.body["value"]
  when "perform"
    CustomClass.perform(event, context)
  when "perform_two"
    CustomClass.perform_two(event)
  when "perform_three"
    CustomClass.perform_three
  end
end

Building and deployment

Taken from another project, use docker to build the bootstrap and upload the zipped file to your aws lambda function:

Build the application

docker run --rm -it -v $PWD:/app -w /app crystallang/crystal:latest \
  crystal build src/main.cr -o lib/mine_train/bootstrap/bootstrap \
    --release --static --no-debug

Zip the deployable bootstrap

zip -j bootstrap.zip lib/mine_train/bootstrap/bootstrap

MineTrain::Lambda::Event

The MineTrain::Lambda::Event type has two public methods:

body

this is the JSON parsed value of the raw event.body

raw

This is the raw event request from the lambda invocation

MineTrain::Lambda::Context

The MineTrain::Lambda::Context type has the following public methods:

function_name

The name of the lambda function

function_version

The version of the lambda function

memory_limit_in_mb

The configured memory for the lambda function

log_group_name

The lambda functions log group

log_stream_name

The log stream for the lambda function

aws_request_id

The unique AWS request ID

invoked_function_arn

The ARN of the invoked function

deadline_ms

The remaining time in mills to complete the lambda function

identity (optional)

The cognito invocation identity

client_context (optional)

The client context of the lambda function

get_remaining_time_in_millis

Method which returns the remaining time to complete the function