reclojure_conf.md

Re-Clojure Conf

Growing Mobile Apps with ClojureScript and React Native - Dan Neal

• Use Expo for React Native
• Shadow-cljs
  • npm libs are easier to use
  • simple config
  • e.g. for externs {:infer-externs :auto}
• Use tachyons for design
• Chrome profiler
• Example app with tools
• Crucial point: app doesn't target desktop, only devices
• REPL most useful for debugging errors on node rather than as RDD workflow

Living in a Box. Life in Containers with the JVM - Matthew Gilliard

• Things that affect startup time matter more in a containerized environment. You should try and move startup activities to build time:
  • Loading Java classes in memory
    • Class Data Sharing (core Java - distributed w/JDK)
    • Application Class Data Sharing (your app)
  • AOT Compilation with Graal
    • use native-image that comes with Graal
    • fast startup, but:
      • worse peak performance
      • potentially worse GC
  • Efficient images
    • small size
      • use an Alpine Linux base image
      • openjdk11:alpine
    • use layers to your advantage
      • copy on write means identical layers are shared
      • so can you, e.g. put dependencies into a layer?
        • a useful tool on github: orb/lein-metajar
        • this means you can create a layer from the dep jars
  • Respect the environment
    • JVM self-tunes (ergonomics) based on
      • available RAM
        • depending on memory, it selects
          • heap space
          • compiler/GC cache sizes
          • which GC to use
      • available CPUs
        • selects:
          • GC/compiler threadpool sizes
          • Runtime::getAvailableCPUs
    • JVM now respects container resource limits in 10, and > Java 8 u212
    • Fun fact, there are 666 JVM args
    • -XX:+PrintFlagsFinal on yr java cmd followed by | grep ergonomic will show you how many JVM flags are set by ergonomics