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Kekkonen ���making your Clojure web APIs more awesome
ClojuTRE 2015Tommi Reiman
@ikitommi
Topics• API all the things!• Challenges• Kekkonen• Done
API all the things!• Clojure(Script) APIs• RPC• Web APIs• REST APIs• Future?
Clojure(Script) APIs• Namespaces and functions (Vars)• Extension via multimethods & protocols• Simple, beautiful, no remoting
RPC• Expose the tagged Clojure functions outwards• Easy remoting• refactoring? external clients?
Web APIs• Map Clojure functions into http endpoints• Thinking in HTTP terms• Swagger docs
REST Apis• Map Clojure functions into resources• Resource containers• Swagger docs (yada!)
Future?• Datomic & DataScript• Falcor/Netflix
– A JavaScript library for efficient data fetching
• Relay/Facebook– A JAVASCRIPT FRAMEWORK FOR BUILDING
DATA-DRIVEN REACT APPLICATIONS
• The Web after Tomorrow– http://tonsky.me/blog/the-web-after-tomorrow/
© Nikita Prokopov
Hmph.• We build complex UIs• Reagent is cool• Need to do remoting, public api-docs too• Business rules need to be enforced both on
server (all) & frontend (part)– Shared code is cool, but number of combinations…
• REST doesn’t even try to solve these issues
CQRS? ���making your Clojure web APIs more awesome
Commands & Queries• http://martinfowler.com/bliki/CQRS.html • Verbs (actions) instead of Nouns (resources)• Command log (auditing) as a bonus• != Event Sourcing• Great for user interactions
– Rules usually per interaction, not resource– Fine-grained à lot’s of actions
© Mar.n Fowler
Commands & Queries
Watch
GiveStar GetRepository
Fork
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Commands & Queries
Watch
GiveStar GetRepository
Fork
Unwatch RemoveStar
[repo-‐id :-‐ s/Str] check-‐repo-‐auth (watched? false)
[repo-‐id :-‐ s/Str] check-‐repo-‐auth
[repo-‐id :-‐ s/Str] check-‐repo-‐auth (watched? true)
[repo-‐id :-‐ s/Str] check-‐repo-‐auth (starred? false)
[repo-‐id :-‐ s/Str] check-‐repo-‐auth
[repo-‐id :-‐ s/Str] check-‐repo-‐auth (starred? true)
ListRespotories
DIY CQRS lib
Rethinking the APIs• Idea– Expose simple Clojure functions as message handlers– Manage handlers in virtual namespaces– Data-driven, no macros, no magic– Explicit extensions via protocols, options and meta-data– Transports abstracted away, http via ring
• Lessons learned from ring-swagger & compojure-api– Clients as first-class citizens
• Remote api documentation as data: rules as data• Public http api documentation via Swagger
Thanks to• Prismatic Schema, (Plumbing)• Elegance of fnhouse• Ring-swagger• Best parts of compojure-api• Schema-tools
Concepts• Handlers & namespaces
– Functions with meta-data, contextàresponse• Context
– A message context consumed by the handler– Opinion: should contain :data –key with the actual payload
• Registry– Collects and enriches handlers into namespaces– Handler invocation & input (pre-)validation– Holds global state
• Ring-adapter– http-bindings for invoking the handlers + schema coercion
• API– Wrapping everything up + exception handling
registry
handler
handler
handler
ns
ns
ns
API
Ring-‐hander
SwaggerUI O
O O
O
CQRS-‐API O
ac.on & context
M
M M
request
Show me
Extensions• Registry/Ring/API Options– Declare things, plug-in transformers
Extensions• Handler & namespace meta-data– Explicit way to extend handler functionality at runtime– Context enrichment, Authorization, Api-doc info, …
HTTP API
Demo
Client-side?• Expose handler data to the clients as clojure (or
JSON) data– list all, available or validated
• Either ask from server or apply the rules for the local dataset– Server: simple, more traffic– Client: shared validation-functions, 2+ datasources
TODO• Finalize the lib (1-2 months?)• Feedback from the community• RE-Kekkonen (a reagent template)• Async (just rewrite the api-middleware)• Event sourcing
Thanks. hVps://github.com/metosin/kekkonen
kekkonen@metosin.fi #ring-‐swagger at Slack @metosin at TwiVer
hiring are we.
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