Short intro to AWS Lambda How to use it with ruby? How to load gems? Problem with native extensions What's the load time? Deploying layers with no downtime?

1. Piotr Wasiak XI 2022
AWS Lambda
How to upload and load gems fast

2. Agenda
AWS loading code and gems
• Short intro to AWS Lambda
• How to load gems
• Problem with native extensions
• What's the load time?
• Deploying layers with no downtime?

3. About.me/Piotr.Wasiak
Ruby (and Rails) developer
• I work currently in SpaceOS.io prop-tech startup
• lambda is used in production to sync sequentially data with external systems

4. AWS Lambda
What is the fuss about
• Reduced complexity. There’s a
fi
xed operating system,
fi
xed software
language, and a
fi
xed version.
• No infrastructure to manage. AWS owns and manages the infrastructure.
You only pay for the time your code runs.
• Implicit scaling. AWS will handle scaling, no matter how much you use your
functions.

5. AWS Lambda
function sca
ff
old
• We can trigger lambda function by:
• Amazon Simple Queue Service
• HTTP Request
• Other Amazon events

6. What about loading libraries
3 ways
• pushing gem sources with code (naive way)
• pushing gems as a layer (pack the sources as zip)
• bundle install --deployment
• zip -FSr gem_layer.zip ./ruby/
• aws lambda publish-layer-version ....
• dockerize lambda image (but hmm it should be without additional setup)

7. Can we use bundler for loading gems?
bundler is by default shiped with ruby
• yes, we can use Gem
fi
le for loading
• on lambda function start:
require 'bundler'
Bundler.require(:default)
• bundler will raise on start if some gem version is missing or wrong
• but you can always require 'gem_name' wherever do you want it

9. First problem with layers
What if we require gems
with native extensions?

10. dependency from Savon
• inside Nokogiri there is also racc
• so there are external libs per
architecture/distributions
Nokogiri

11. Solution
• use aws-lambda docker to generate libs
• bundle con
fi
g set --local clean 'true'
• zip & push it as layer
Nokogiri depedency

12. Second problem with ruby
What is really the load time
of lambda function

13. Before adding native extentions
Loading time ~ 1050 ms

14. After adding native extentions
Loading time ~ 1550 ms

15. Our Gemfile right now
> bundle install --without test
(...)
Using activesupport 7.0.4
Using nokogiri 1.13.9 (arm64-darwin)
Using aws-sdk-core 3.166.0
Using faraday 2.6.0
Using graphql 2.0.15
Using savon 2.13.1
(...)
Using sentry-lambda 0.2.1
Using warning 1.3.0
Using zeitwerk 2.6.4
Bundle complete! 14 Gem
fi
le dependencies, 38 gems now installed.
Gems in the group 'test' were not installed.

16. Autoloader to load only required files
Zeitwerk Solution
• Convention to store required classes in proper folders
• load on usage and don't load twice (even if it has di
ff
erent require path)

17. After adding Zeitwerk (code autoloader)
Loading time ~ 1350 ms

18. Load gems only if needed
Solution
• skip requiring Nokogiri and GraphQL in Gem
fi
le (on boot)
• manual require in service
fi
les

19. With autoloader skipping Savon, GraphQL
Loading time ~ 820 ms Faster than 6 month ago :O

20. Third problem with layers
How to ensure no downtime
with releasing new libs and code

21. How to release new layer with code
Solutions
1. Combine together previous layer with new one and ship combined layer
fi
rst
• can be incompatible with API changes (test it
fi
rst)
• no downtime at all
• have to use bundler (require does not know which gem version should be loaded)
2. Push new layer
and switch it just before pushing the new function code
• there is no way to push the code and switch to new layer in one transaction
• very small downtime (already started functions will be
fi
ne during that change)
3. Use lambda function versions and just switch event trigger to new code version with layer

22. Take aways
• Lambda loading time
for ruby is more 0,5 sec
• Loading gems with layers
provides some challenges
• If you have complex app
then go with lambda docker

23. Sources
• https://stackify.com/aws-lambda-with-ruby-getting-started-guide
• https://docs.aws.amazon.com/lambda/latest/dg/lambda-ruby.html
• github.com aws-lambda developer-guide/sample-ruby
• https://github.com/fxn/zeitwerk#awards
• https://bundler.io

24. Thanks for listening