HTPS Keynote

Before

• Storage has evolved
  • (from Direct, SAN, Storage clusters + REST API)
• Computing Evolved
  • Single proc -> Multi -> RPC -> SOA -> Microservices
• Computing Storage Use
  • Direct File I/O

State

• Durable state + consistency (transactions/updates/message semantics)
• Session State - multi op transactions; sessions are hard @ microservices
• inside/outside data
  • outside data is immutable

Careful Replacement

• disks can trash block during write: (old -> trash -> new)
• hardware fixes careful replacement issue
• transactions bundle + solve careful replacement
• workflows need careful transactional replacement now

Read your writes?

• Strong consistently - (R after W):
  • Even as scales you can r after w
  • Sometime delay if sick/dead (releader election)
• Weakly consistent (not R after W):
  • No guarantee write update old replica - read old value
  • R/W consistent SLA - skip sick/dead servers
• Cached Data
  • KV pairs versioned, unsure if newest.

Different stores for diff uses! Immutability can fix these - only one version to get.

Stateful Sessions And Transactions

• Stateful sessions worked well for SOA: Distributed Transactions + Across Machines

Transactions, Sessions, Microservice

• Requests flow to request routing.
• Session state needed for cross-request TV
• Microservice Transaction are typically 1 store request
• No cross request transactions

Theres no substitute for interchangibility