Using Ruby to build AWS lambda along with mysql2

AWS Lambda added Ruby to the list of supported languages at the end of the year 2018. The official document does a good job in explaining how to get started with it. However, it doesn't cover how to include gems that have dependencies on native extensions, like mysql2.

The scope of the post is to demonstrate how to make mysql2 gem work with Lambda. And, it uses RDS to achieve this. It is assumed that the reader has prior experience with AWS services and the following topics will be excluded in the post.

• Creating an RDS instance.
• Configuring Lambda function to connect to RDS.

Lets get started.

1. Create a new folder and change the working directory to the same.

     mkDir sample_ruby_lambda
     cd sample_ruby_lambda
   

2. Install RVM, Ruby, and Bundler.

     rvm install ruby-2.5.0
     gem install bundler
   

3. Install Docker.

4. Create a Docker file(Dockerfile).

    FROM lambci/lambda:build-ruby2.5RUN yum -y install mysql-devel
    RUN gem update bundlerCMD "/bin/bash"
   

5. Create a Docker image.

     docker build -t lambda-ruby2.5-sales-dashboard .
   

6. Create a ruby handler file(handler.rb)

     require 'mysql2'def main(event:, context:)
       # client = Mysql2::Client.new(
       #   :host => "******.us-east-*.rds.amazonaws.com",
       #   :username => "********",
       #   :database=> "*******",
       #   :password=> "**********",
       #   :port => 3306)
       # results = client.query("SELECT COUNT(*) FROM employees;").to_a
       {
         test: Mysql2::VERSION
       }
     end
   

7. Create a Gemfile(Gemfile)

     source "[https://rubygems.org](https://rubygems.org/)"gem "mysql2"
   

8. Using RVM use the ruby-2.5.0(If not present instal it)

     rvm use ruby-2.5.0
   

9. Execute the following command to get inside the container:

     docker run --rm -it -v $PWD:/var/task -w /var/task lambda-ruby2.5-sales-dashboard
   

10. From inside the container, run;

      bundle config --local build.mysql2 --with-mysql2-config=/usr/lib64/mysql/mysql_config
      bundle config --local silence_root_warning true
      bundle install --path vendor/bundle --clean
      mkdir -p /var/task/lib
      cp -a /usr/lib64/mysql/*.so.* /var/task/lib/
    

11. Smoke test: Run the following inside the container.

      ruby -e "require 'handler'; puts main(event: nil, context: nil)"
    

12. You should get a response like this,

      { test: "0.5.2" }
    

13. Package to Zip.

      rm -f deploy.zip
      zip -q -r deploy.zip .
    

14. Exit the container bash and simulate the lambda instance.

      docker run --rm -v "$PWD":/var/task lambci/lambda:ruby2.5 handler.main
    

    You can expect the following result

      START RequestId: 52fdfc07-2182-154f-163f-5f0f9a621d72 Version: $LATEST
      END RequestId: 52fdfc07-2182-154f-163f-5f0f9a621d72
      REPORT RequestId: 52fdfc07-2182-154f-163f-5f0f9a621d72
      Duration: 7.85 ms Billed Duration: 100 ms Memory Size: 1536 MB Max Memory Used: 21 MB
      {"test":"0.5.2"}
    

15. Deploy to the AWS Lambda using the console, or command line

16. Go to AWS lambda console and test the code.