Peeling back the Lambda layers
- 1. Peeling back the lambda layers
- 2. Who am I Javascript developer Forsite -> Accordo Now learning ML Working from home
- 3. • Layers 🍰 • Lambda functions • Containers • Lambda Layers • Case study: PDF generation on Lambda • The problem • The solution • Adding more layers to the solution • Conclusions 🤔
- 4. Faas: Functions as Service • Pick a runtime • Write your code • Upload code + dependencies
- 5. The metaphor Lambda functions have layers
- 8. Lambda function lifecycle • Cold start • Starts a new container • AWS downloads your code & Extracts it to dir /var/task • AWS bootstraps the runtime ( nodejs, python etc) • Hot start • Runs your handler code
- 10. Lambda Layers • Another way to add code to your function
- 11. Lambda Layers • Another way to add code to your function
- 12. Lambda Layers • 2 stages • Create layer/s • Use layer in your lambda function
- 13. Lambda Layers • Upload a zip, just like a function bundle • This creates a Layer ARN • Create a layer
- 14. Lambda Layers • Use a layer • Reference a layer ARN in function definition • When your function runs • Layer code is downloaded to /opt/<layer_name> • Your function has access to any files in the layer serverless.yml
- 15. Lambda Layer Limits • Layers count toward max unzipped limit of 250mb • Max 5 layers per function • Layers are uploaded for a region and a runtime • e.g us-west-2/node:8.11.1
- 16. Lambda Layer • What's nice? • Simple way to reuse dependencies in your functions • Separate your dependencies into layers • Smaller bundles to deploy each time • What’s not nice? • No semantic versioning, just increments witch each deploy 1,2,3,4,5. Not so bad • Now your function isn’t Bring Your Own Code, doesn’t own all its dependencies
- 18. PDF generation on Lambda • Backend service on EC2 ( Beanstalk ) • Generated pdf reports for customers • Multi language support - Non English fonts! • New Features were planned
- 19. PDF generation on Lambda Original solution • Node express app • Non Node external lib for HTML - > PDF generation: wkhtmltopdf • Multi language fonts: Thai, Jap, Korean • To render fonts with wkhtmltopdf we need to install system fonts with fontconfig
- 20. PDF generation on Lambda • Tech Debt to be paid • Sometimes the EC2 instance would restart and lose the font cache ! • To fix • Ssh into live instance ( dev, uat, prod ) 😰 • Manually install the fontconfig fonts from the terminal 😭 • Non standard deployment model, only EC2 instance
- 21. Migrate to Lambda • New Features planned • Good candidate • It is stateless web-server • Not too many requests, probably save money • Devops • Doesn’t follow the standard deployment model • Teams know serverless
- 22. Migrate to Lambda • What we need to solve: • Node Express app -> handler function • Wrap It with npm package • don’t want to rewrite the whole thing • External Binary: wkhtmltopdf • Need to have the correct binary for lambda container OS! • What distro is closest to amazon linux? • System Fonts: Fontconfig • Wkhtmltopdf relies on system fonts • Linux uses fontconfig lib to render • Need to build the correct font files! • How will we test it?
- 23. A note on Testing • Lambda function testing is usually great! • Exact runtime version as lambda • Event mocking libraries e.g. lambda-local • Our integration tests give great confidence • What if we are using non supported binaries?
- 24. Implementation • Wrap Express app -> function • Mimic lambda container runtime: • Check our binary executes • Build our fonts and check they render • Local testing • Mock a lambda event and run our function from the lambda container
- 25. Implementation • Wrap Express app -> function ✅ • Use an npm package to wrap our server
- 26. Lambda docker container • Mimic lambda container runtime: • Check our binary executes ✅ • Community made container that aims to mimic the runtime • Run docker container and Check Binary • We can test if it works locally! • You could also build from source…
- 27. Implementation • Mimic lambda container runtime: • Build our fonts and check they render
- 28. Lambda docker container • Build our fonts in this container • Way better than manual • Reproducible 🙌 • Reference the location of our new fonts
- 29. Implementation • Wrap Express app -> function ✅ • Mimic lambda container runtime: • Check our binary executes ✅ • Build our fonts and check they render ✅ • Local testing • Mock a lambda event and run our function from the lambda container
- 30. Implementation • Local testing • Mount all our code, font files, dependencies in docker container • /var/task/ • Use lambda-local package to mock a lambda event • it works 🌈 🌈 🌈 🌈 🌈 🌈 🌈 🌈 ( sorry no demo )
- 31. Deploy • Our bundle • Node Code • Fontconfig files • Binary: wkhtmltopdf • Works in live * Generated from lambda function 🙌
- 32. The end
- 33. What about Lambda Layers? • It already works, we could stop here… • We added a lot of complexity • Could reuse these bespoke lambda dependencies • They change infrequently just add to bundle size
- 34. What about Lambda Layers? What our function looks like now
- 35. What about Lambda Layers? What our function could look like with lambda layers
- 36. Build our layers • build files • Upload with serverless
- 37. Add layers to Function • Get the layer ARN • Add to function definition • Add env vars to reference layer code
- 38. Add layers to Function
- 39. Separate
- 40. Local Testing
- 41. Local Testing • Layers only accessible in LIVE • Our function doesn’t include all its dependencies locally • Now our local testing doesn’t have the layer code?? • Local lambda mocking libraries support layers?
- 42. Local Testing • We can hack a solution together • download layers with aws-cli • mount them in our local lambda container like AWS does • /opt/<layer_name> • Run like before
- 43. CONCLUSIONS Container to serverless • Deployed non supported binary 🌈 • Replicated lambda env on our local for testing • Possibilities infinite and bounded ( 250mb max size unzipped)
- 44. CONCLUSIONS • What did we achieve with lambda layers? • Share our layer code • Share to other functions super easy • standard dependencies across services . e.g. standardised for security • Separated our concerns • Decreased our bundle size • Added local testing overhead ( but already have extra with non supported binaries )
- 45. A healthy compromise • Between • Container orchestration overhead • managing the added complexities of non standard dependencies The complexity doesn’t go away, but it might be worth it for your teams