How can I get my AWS Lambda to access gems stored in vendor/bundle?

Question

I'm writing a Lambda function in Ruby which will eventually send me some notifications in Slack via Webhook. So what I have for my lambda_function file is

require 'json'
require 'webhook'

def lambda_handler(event:, context:)
    # TODO implement
    { statusCode: 200, body: JSON.generate('Hello from Lambda!') }
    Webhook.post('https://mywebhookurl', {message: 'test'})
end

And the directory structure in my inline code editor looks like this:

Gemfile
Gemfile.lock
lambda_function.rb
vendor/
  bundle/
    ruby
      2.3.0
        gems/webhook

also under the 2.3.0 bath are several other folders including build_info, cache, doc etc. In order to get this code onto AWS Lambda, I'm running

zip -r myLambda.zip * to get everything into a zip file and uploaded to Lambda.

However, when I finally go to run a basic test on the lambda, I get the following error:

{
  "errorMessage": "cannot load such file -- webhook",
  "errorType": "Init<LoadError>",
  "stackTrace": [
    "/var/lang/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in `require'",
    "/var/lang/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in `require'",
    "/var/task/lambda_function.rb:2:in `<top (required)>'",
    "/var/lang/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in `require'",
    "/var/lang/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in `require'"
  ]
}

There shouldn't be any more to this as the following tutorial shows exactly how to set up what I have, but doesn't work. Does anyone have success pulling gems from their gemfile in AWS Lambda?

Answer 1

I think you should not change the GEM_PATH or having to set $LOAD_PATH in every lambda functions. The "best" way is to do this little hack when you create the layer archive:

bundle install --path vendor/bundle
cd vendor/bundle
mkdir ruby/gems
mv ruby/2.5.0 ruby/gems/
zip -r layer.zip ruby/gems/2.5.0/