Domain Driven Design in Clojure: Amit Rathore

• read the book from eric evans
• Lot of oop design principles carry over
• shoot for 3-4 lines of clojure code per function
• validateur, bouncer, clj-schema (validation)
• if code confusing, demand simplification
• make temp namespaces explicit: zolo.homeless
• domain: business-important logic, not the API, not services, not validation, not talking to the db, just the stuff business people care about; should be pure
• if you don’t need it now, don’t build it

RESTful Clojure: Siva Jagadeesan

• liberator, bishop: libraries to help build proper REST APIs in clojure
• use the status codes: 1xx – Metadata, 2xx – success, 3xx – redirect, 4xx – client error, 5xx – server error
• 405: method not allowed
• 409: conflict
• 404: resource not present
• create returns Location header with location of new resource, in addition to the 201 (created) status code
• even better: also return a set of links to related resource (rel = self) and transitions (rel = cancel)
• allows client to be loosely coupled from API
• client doesn’t need to know how resources move through the system (transition logic)
• REST means using multiple URIs, HTTP status codes, and Hypermedia

Clojure in the Large: Stuart Sierra

• def’ing refs and atoms at the top level is basically global mutable state via singletons, please avoid
• recommend using constructor functions to *return* the state variables you want to use, then pass that state along to each function
• easier to test
• explicit dependencies
• safe to reload when working at the repl
• thread-bound state also bad: assumes no lazy sequence returned in function bodies, hides dependencies, and limits caller to using one resource at a time
• prefer passing context around to functions
• can pull resources out of it
• use namespace-qualified keys for isolation
• isn’t confined to a single thread
• still need to cleanup at the end
• more bookkeeping
• true constants are fine as global vars (^:const)

Pedestal: Architecture and Services: Tim Ewald

• alpha release from relevance of open-source libs
• use clojure end-to-end to build RIAs
• demo: hammock cafe: clojurescript apps communicating to same back-end using datomic store
• 2 halves: pedestal-service, pedestal-app
• ring limits: bound to a single thread’s stack
• interceptors: map of functions, has enter and leave for processing requests and responses
• can pause and resume along any thread
• pushed to be as ring-compatible as possible
• use of long polling and server-side events (requests that come in slow and last a long time, get updated as more data comes in)

Design, Composition, and Performance: Rich Hickey

• take things apart
• design like bartok (embrace constraints, use harmonic sense)
• code like coltrane (constant practice, keep harmonic sense)
• build libraries like instruments (design for players, able to be combined with other things)
• pursue harmony