Joseph Wilk The Clojure Inside Why Clojure? It was Functional - - PowerPoint PPT Presentation

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Joseph Wilk The Clojure Inside Why Clojure? It was Functional - - PowerPoint PPT Presentation

Nov 25, 2022 115 likes •709 views

Joseph Wilk The Clojure Inside Why Clojure? It was Functional Immutable there! Simple LISP Concurrency It was Functional Immutable there! Simple LISP Concurrency Programming Language Computer LISP Hurts (Pick languages that

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Joseph Wilk

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The Clojure Inside

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Why Clojure?

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LISP Concurrency Immutable Functional Simple

It was there!

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LISP Concurrency Immutable Functional Simple

It was there!

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Programming Language Computer

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LISP Hurts

(Pick languages that challenge your mental model) (( ))

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(defn filter "Returns a lazy sequence of the items in coll for which (pred item) returns true. pred must be free of side-effects." {:added "1.0" :static true} ([pred coll] (lazy-seq (when-let [s (seq coll)] (if (chunked-seq? s) (let [c (chunk-first s) size (count c) b (chunk-buffer size)] (dotimes [i size] (when (pred (.nth c i)) (chunk-append b (.nth c i)))) (chunk-cons (chunk b) (filter pred (chunk-rest s)))) (let [f (first s) r (rest s)] (if (pred f) (cons f (filter pred r)) (filter pred r))))))))

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SLIDE 10 (defmacro doseq "Repeatedly executes body (presumably for side-effects) with bindings and filtering as provided by \"for\". Does not retain the head of the sequence. Returns nil." {:added "1.0"} [seq-exprs & body] (assert-args (vector? seq-exprs) "a vector for its binding" (even? (count seq-exprs)) "an even number of forms in binding vector") (let [step (fn step [recform exprs] (if-not exprs [true `(do ~@body)] (let [k (first exprs) v (second exprs)] (if (keyword? k) (let [steppair (step recform (nnext exprs)) needrec (steppair 0) subform (steppair 1)] (cond (= k :let) [needrec `(let ~v ~subform)] (= k :while) [false `(when ~v ~subform ~@(when needrec [recform]))] (= k :when) [false `(if ~v (do ~subform ~@(when needrec [recform])) ~recform)])) (let [seq- (gensym "seq_") chunk- (with-meta (gensym "chunk_") {:tag 'clojure.lang.IChunk}) count- (gensym "count_") i- (gensym "i_") recform `(recur (next ~seq-) nil 0 0) steppair (step recform (nnext exprs)) needrec (steppair 0) subform (steppair 1) recform-chunk `(recur ~seq- ~chunk- ~count- (unchecked-inc ~i-))

wee wee

wee wee wee wee wee

wee wee

Code generation Code is data Data is code Functions what do functions Variable generation Is that a class?

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OH MY ITS FAST

(Jetty/Netty but sssssh) (Shhh confirmation Bias)
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History

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Rails Me

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Rails Me

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Ruby

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Small Replaceable Pieces

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Experiment

A B ?

Opening (Divergent) Exploring (Emergent) Closing (Convergent)

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Clojure

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Hystrix Turbine RxJava Netty Aleph Compojure

https://github.com/Netflix/Hystrix https://github.com/Netflix/Turbine https://github.com/Netflix/RxJava https://github.com/ztellman/aleph https://github.com/weavejester/compojure http://netty.io

Midje

https://github.com/marick/Midje

Ring

https://github.com/ring-clojure/ring

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Maturity Brevity + & Denial (its not Java)

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atom quote eq car cdr cons cond lambda label apply

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Java Denial

(defmacro)
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HttpServer server = HttpServer.create(address, 0) server.createContext(path, handler); server.setExecutor(null) server.start(); (doto (HttpServer/create address 0) (.createContext path handler) (.setExecutor nil) (.start))

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HttpServer server = HttpServer.create(address, 0) server.createContext(path, handler); server.setExecutor(null) server.start(); (doto (HttpServer/create address 0) (.createContext path handler) (.setExecutor nil) (.start))

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public class GetSoundCmd extends HystrixCommand<Sound> { private final HttpClient client; private final String urn; public FindSoundCmd(HttpClient client, String urn){ this.client = client; this.urn = urn; } @Override protected Sound run(){ return client.get("/sounds/" + urn, Sound.class) } @Override protected Sound getFallback(){ return Sound.missing(id); } } new GetUserCmd(client, id).execute(); (:require [com.netflix.hystrix.core :as hystrix]) (hystrix/defcommand find-sound {:hystrix/fallback-fn #(constantly {}))} [client urn] (http/get urn)) (get-sound client "soundcloud:sounds:123")

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public class GetSoundCmd extends HystrixCommand<Sound> { private final HttpClient client; private final String urn; public FindSoundCmd(HttpClient client, String urn){ this.client = client; this.urn = urn; } @Override protected Sound run(){ return client.get("/sounds/" + urn, Sound.class) } @Override protected Sound getFallback(){ return Sound.missing(id); } } new GetUserCmd(client, id).execute(); (:require [com.netflix.hystrix.core :as hystrix]) (hystrix/defcommand find-sound {:hystrix/fallback-fn #(constantly {}))} [client urn] (http/get urn)) (get-sound client "soundcloud:sounds:123")

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Interactivity

R read E evaluate P print L loop

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Services at scale

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Grace in the face of failure

high partition tolerance in a high latency cloud network (don't trust anything works)
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Threadpool (future (fn [] "from the future")) (promise) (agent)

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Threadpool 100 threads

Bulkhead

Threadpool 10 threads Threadpool 10 threads Threadpool 30 threads Scheduler queue

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(hystrix/defcommand find-user {:hystrix/fallback-fn (constantly {})} [user-urn] (let [response (get-user user-urn)] (if (= 200 (:status response)) (:body response) {}))) (find-user 123) (hystrix/queue #‘find-user 123) (defn find-user [user-urn] (let [response (get-user user-urn)] (if (= 200 (:status response)) (:body response) {})))

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(hystrix/defcommand find-user {:hystrix/fallback-fn (constantly {})} [user-urn] (let [response (get-user user-urn)] (if (= 200 (:status response)) (:body response) {}))) (find-user 123) (hystrix/queue #‘find-user 123) (defn find-user [user-urn] (let [response (get-user user-urn)] (if (= 200 (:status response)) (:body response) {})))

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(hystrix/defcommand find-user {:hystrix/fallback-fn (constantly {})} [user-urn] (let [response (get-user user-urn)] (if (= 200 (:status response)) (:body response) {}))) (find-user 123) (hystrix/queue #‘find-user 123) (defn find-user [user-urn] (let [response (get-user user-urn)] (if (= 200 (:status response)) (:body response) {})))

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Consumers

Service X

Turbine DNS Dashboard

Service X Service X Service X Service X

metrics discovery

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SLIDE 42 https://github.com/Netflix/Hystrix
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Compositional Complexity

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a c b d g f e

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a c b d g f e

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a c b d g

zip map

List Processing

zip

e

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List Processing

a c b d g

zip map zip

e

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LisP

a c b d g

zip map zip

e

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RxJava

(map) (zip) (filter) (partition) (reduce)

https://github.com/Netflix/RxJava
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a c b d g

zip map zip

e

  • n-error
  • n-complete

Ending Callback Hell

(.subscribe (fn [result] (enqueue channel {:status 200 :body (json/encode result}) (fn [error] (log/exception error request))))))

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SLIDE 52 https://github.com/ztellman/aleph

Request & Response

(.subscribe (fn [result] (enqueue channel {:status 200 :body (json/encode result}) (fn [error] (log/exception error request)))))) (defn handler [request] {:status 200 :body "Hello World"}) (use 'lamina.core) (defn handler [response-channel request] (enqueue response-channel {:status 200 :body "Hello World"}))

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SLIDE 53 https://github.com/ztellman/aleph

Request & Response

(.subscribe (fn [result] (enqueue channel {:status 200 :body (json/encode result}) (fn [error] (log/exception error request)))))) (defn handler [request] {:status 200 :body "Hello World"}) (use 'lamina.core) (defn handler [response-channel request] (enqueue response-channel {:status 200 :body "Hello World"}))

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SLIDE 54 https://github.com/ztellman/aleph

Request & Response

(.subscribe (fn [result] (enqueue channel {:status 200 :body (json/encode result}) (fn [error] (log/exception error request)))))) (defn handler [request] {:status 200 :body "Hello World"}) (use 'lamina.core) (defn handler [response-channel request] (enqueue response-channel {:status 200 :body "Hello World"}))

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SLIDE 55 https://github.com/ztellman/aleph

Request & Response

(.subscribe (fn [result] (enqueue channel {:status 200 :body (json/encode result}) (fn [error] (log/exception error request)))))) (defn handler [request] {:status 200 :body "Hello World"}) (use 'lamina.core) (defn handler [response-channel request] (enqueue response-channel {:status 200 :body "Hello World"}))

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Clojure Itches

Its upside down attern matching Corrupts your brain parameter redeye

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Clojure

One of the many paths

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Joseph Wilk