Ruby Conf 2024

HTML for performance

• less 2000nodes, warnings at 800 nodes
• max depth of 32 nodes
• dont use divs
• cumulative layout shift
• img .. loaging=”lazy”
  • !!! do not lazy load LCP (Largest ..)
• prioritisation is very important on http 2/3
  • fetchpriority: high / low / auto(default) high / low will only raise to specfied amount, not max - use in img carousels, etc
• <link rel="preconnect" -> 100ms gains
  • only for critical fetches
  • for rest use <link rel="dns-prefetch"
  • <link rel="preload" on critical
    • for fonts, css, large vids/files
    • not for ordinary media

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Anti-patterns

SQL / n+1 / optimisation

1. bullet gem
2. strict loading
3. rack-minni-profiler and stackprof gems

Law of Demeter

order.smth.name
order.smth.other.name
order.smth.other.date

order.try(:smth).try(:name)

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Fibres vs Threads

avoiding deadlock with threads

1. acquire lock in order
2. set timeout
3. use appropriate data structs

   avoiding deadlock with fibres

   • fibres needs explicit yeild

interrupts

fibres less succeptible to interrupts

handle interrupts in threads

• use flags
• maintain timeouts
• use thread#kill
• maintain queue

threads - complex to debug fibres - no native parallelism support fibres aren’t useful in compute heavy operations thread are not good at optimizing CPU utilization fibres need explicit coordination fibres has no shared memory(share mem leads to issues)

Ractors

async, async-http, async-io - gem, built on top of fibres falcon - server

Scaling Redis writes with Cluster mode

way to deploy Redis

• 1:1 - Rails:Redis
• Redis Sentinel: high availability (old school) - works out of the box with redis gem.
  • Cons: no way to scale writes
  • Pros: can sxale reads from stale replica. no single point of filure
• Redis::Distributed: A-K, L-Z
• Redis::Distributed + Redis Sentinel
  • problem: node scaling. A-K, L-Z, ???
• Redis Cluster (gem)
  • 16384 slots crc16(key)
  • each slot is assigned to one master node and some replica nodes

    cons: complicates client lib support to correctly handle redirections