Course: Advanced Distributed System Design - Udi Dahan
Coupling
incoming vs outgoing coupling
def: incoming coupling
def: outgoing coupling
clarity: incoming vs outgoing
count coupling X->Y x outboing 1 y incoming 1
A->B x outgoing 5 “is this class single responsibility principle” y incoming 1 “how many classes do I have to change”
static analysis tool
hidden coupling
3 aspects of coupling
aspect 1: platform (aka interoperability)
text-based representation on the wire http, smtp, udp, …
soap / wsdl / rest
apect 2: time
aspect time: Pub-Sub explicit caching
make explicit in A that caching is happening
aspect time: Pub-Sub constraints
aspect time: Pub-Sub add validity period to data
aspect time: Pub-Sub consitency
if pub sub not OK time-constraint, then RPC also not OK (can use cache) -> transaction across A and B needed
aspect space: routing
aspect time: logical owner logical owner
coupling 5 dimensions tradeoffs tradeoffs between dimensions per ‘’layer" keep LOGIC away from all the other “is the coupling reasonable for it’s responsibility” eg. fromend webapi, platform low, even if HTTP response which is time high coupling internal component: low temporal at cost of higher platform (pub-sub platform framework)
