Clojure among Java

A story of applying Clojure within a pure Java environment (primarily among Tomcat servlets) with practical recommendations and emphasis on ease of introspection and using the app in production.

Transcript

1. Clojure among Java @darkproger
2. Hi! I happen to use JVM.
3. Enterprise
6. FAIRY TALE WARNING
7. Y U NO Java? Boilerplate IDE Tooling Time
8. o_O →
10. o_O → Java → Clojure
11. maven IDE XML boardom → leiningen → text editor → clj forms (EDN) → pun
12. enterprise →
13. HTTP
14. HTTP adapters CGI FastCGI SCGI WSGI Rack Servlet Ring ISAPI Apache Modules
15. JSR 315 Java Servlet 3.0 Spec http://jcp.org/en/jsr/detail?id=315
16. JSR 315 Java Servlet 3.0 Spec http://jcp.org/en/jsr/detail?id=315 (230 pages)
17. github: ring-clojure/ring https://github.com/ring-clojure/ring/blob/master/SPEC
18. github: ring-clojure/ring https://github.com/ring-clojure/ring/blob/master/SPEC (120 lines)
19. (defn handler [{headers :headers method :request-method body :body :as request-map}] {:status 200 :body "ok computer"})
21. Tomcat
23. local.MyServlet.service org.apache.catalina.core.ApplicationFilterChain.internalDoFilter org.apache.catalina.core.ApplicationFilterChain.doFilter org.apache.catalina.core.StandardWrapperValve.invoke org.apache.catalina.core.StandardContextValve.invoke org.apache.catalina.authenticator.AuthenticatorBase.invoke org.apache.catalina.core.StandardHostValve.invoke org.apache.catalina.valves.ErrorReportValve.invoke org.apache.catalina.valves.AccessLogValve.invoke org.apache.catalina.core.StandardEngineValve.invoke org.apache.catalina.connector.CoyoteAdapter.service org.apache.coyote.http11.AbstractHttp11Processor.process org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run java.util.concurrent.ThreadPoolExecutor.runWorker java.util.concurrent.ThreadPoolExecutor$Worker.run java.lang.Thread.run
25. github: weavejester/lein-ring https://github.com/weavejester/lein-ring
26. % cat project.clj (defproject web "0.1.0-SNAPSHOT" :dependencies [[org.clojure/clojure "1.5.1"] [org.clojure/tools.nrepl "0.2.2"] [digest "1.3.0"] [ring "1.2.0-beta2"] [ring/ring-servlet "1.2.0-beta2-SNAPSHOT"] [clj-stacktrace "0.2.5"] [compojure "1.1.5"]] :plugins [[lein-ring "0.8.5-SNAPSHOT"] [lein-checkouts "1.1.0"] [lein-checkout-deps "1.0.0"]] :ring {:handler web.core/handler :web-xml "resources/web.xml"})
27. % lein ring uberwar
28. Async webbit aleph http-kit (mostly java)
29. Ring Adapters ring-jetty ring-servlet ring-netty ring-httpcore ring-mongrel2
30. Ring Adapters ring-jetty ring-servlet ring-netty ring-httpcore ring-mongrel2
31. github: proger/ring /ring-servlet https://github.com/proger/ring/tree/servlet-async/ring-servlet
32. Introspection
34. Java RMI jstatd + rmiregistry JMX
35. Desperate Java java -agentlib:jdwp=\ transport=dt_socket,\ address=8000,\ server=y,\ suspend=n
36. java -cp jline.jar:tools.jar jline.ConsoleRunner com.sun.tools.example. debug.tty.TTY -attach 8000 Desperate Java
37. BTrace: Bytecode tracing kenai.com/projects/btrace/
38. DTrace + hotspot provider + jstack() (solaris/osx) % env \ LD_AUDIT_64=/usr/lib/dtrace/64/libdtrace_forceload.so \ java -XX:+ExtendedDTraceProbes
39. DTrace + hotspot provider + jstack() ( solaris) % env \ LD_AUDIT_64=/usr/lib/dtrace/64/libdtrace_forceload.so \ java -XX:+ExtendedDTraceProbes % vagrant box add omnios \ http://omnios.omniti.com/media/omnios-latest.box
40. Inject a Clojure agent in live Java github: djpowell/liverepl https://github.com/djpowell/liverepl
41. nREPL
44. % lein repl nREPL server started on port 63155 REPL-y 0.1.10 Clojure 1.5.1 Exit: Control+D or (exit) or (quit) Commands: (user/help) Docs: (doc function-name-here) (find-doc "part-of-name-here") Source: (source function-name-here) (user/sourcery function-name-here) Javadoc: (javadoc java-object-or-class-here) Examples from clojuredocs.org: [clojuredocs or cdoc] (user/clojuredocs name-here) (user/clojuredocs "ns-here" "name-here") user=>
45. % lsof -nPi | grep 63155 java 35453 proger 27u IPv6 0x94fc11a576507639 0t0 TCP 127.0.0.1:63155 (LISTEN) java 35453 proger 32u IPv6 0x94fc11a576506e79 0t0 TCP 127.0.0.1:63157->127.0.0.1:63155 (ESTABLISHED) java 35453 proger 33u IPv6 0x94fc11a54fec6259 0t0 TCP 127.0.0.1:63155->127.0.0.1:63157 (ESTABLISHED)
46. (def nrepl-agent (safe-agent {})) (defroutes api (POST "/nrepl" _request (when (nil? (:nrepl @nrepl-agent)) (send-off nrepl-agent (fn [mp] (assoc mp :nrepl (nr/start-server)))) (await nrepl-agent)) (plain-text @nrepl-agent))
47. % curl -X POST http://tomcat.local/app/nrepl {:nrepl #clojure.tools.nrepl.server.Server{ :server-socket #<ServerSocket ServerSocket[addr=0.0.0.0/0.0.0.0,port=0,localport=63798]>, :port 63798, :open-transports #<Atom@ef4100a: #{}>, :transport #<transport$bencode clojure.tools.nrepl.transport$bencode@5148c277>, :greeting nil, :handler #<middleware$wrap_conj_descriptor$fn__304 clojure.tools.nrepl.middleware$wrap_conj_descriptor $fn__304@bb92b69>, :ss #<ServerSocket ServerSocket[addr=0.0.0.0/0.0.0.0,port=0,localport=63798]>}}
48. % lein repl :connect 63798 REPL-y 0.1.10 Clojure 1.5.1 reply.eval-modes.nrepl=> (ns app.core) nil app.core=> (ns-publics *ns*) {handler ...}
49. % lein repl :connect 63798 ... app.core=> (add-classpath "file:/tank/ proger/.m2/repository/org/clojure/tools.trace/ 0.7.5/tools.trace-0.7.5.jar") nil app.core=> (use 'clojure.tools.trace) nil app.core=> (trace-ns *ns*) nil ; watch STDOUT! app.core=> (untrace-ns *ns*) nil https://github.com/cemerick/pomegranate http://clojure.github.io/tools.trace/
51. k thx bai! @darkproger kirillov.im github.com/proger
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54. Legal http://www.camunda.com/wp-content/uploads/2012/08/java.gif http://www.youtube.com/watch? feature=player_detailpage&v=gZy2I8csVQU#t=4s http://slant.investorplace.com/files/2013/03/Enterprise_5_hr.jpg http://d310a9hpolx59w.cloudfront.net/product_photos/1952530/ Mustache_20_2B_20Glasses_original.png (derived) http://joyent.com/blog/friday-funday-the-origins-of-the-dtrace-pony https://si0.twimg.com/profile_images/1246802441/lisp_.png http://www.deargrumpycat.com/wp-content/uploads/2013/04/Grumpy- Cat.jpg http://content.comrz.com/AcuCustom/Sitename/DAM/374/ApacheTomcat.png http://blog.catmoji.com/wp-content/uploads/2012/09/lying-tard.jpeg http://2.bp.blogspot.com/-iNP88dCJP3Y/Tbz_heuq9HI/AAAAAAAABRM/ jtyOOhjEyKA/s1600/Portal-2%255B1%255D.jpg