CRaSH the shell for the Java Virtual Machine

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    10-May-2015
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A presentation from Julien Viet - www.exoplatform.com CRaSH is the open source shell for the JVM. The shell can be accessed by various ways, remotely using network protocols such as SSH, locally by attaching a shell to a running virtual machine or via a web interface. Commands are written Groovy and can be developed live making the extensibility of the shell easy with quick development cycles. Since the version 1.3, the REPL also speaks the Groovy language, allowing Groovy combination of command using pipes. CRaSH comes with commands such as thread management, log management, database access and JMX. The session will begin with an introduction to the shell. The main part of the session will focus on showing CRaSH commands development with few examples, showing how easy and powerful the development is. The audience will learn how to use CRaSH for their own needs: it can be a simple usage or more advanced like developing a command or embedding the shell in their own runtime like a web application or a Grails application.

Transcript of CRaSH the shell for the Java Virtual Machine

  • 1.w w w . c r a s h u b . o r g CRaSH The shell for the JVM w w w . c r a s h u b . o r g Julien Viet exoplatform

2. w w w . c r a s h u b . o r g All semicolons characters appearing in this work are fictitious. Any resemblance to real characters, living or dead, is purely coincidental. Disclaimer 3. w w w . c r a s h u b . o r g http://www.julienviet.com / @julienviet 10 years of portal development (you know Portlets) Working at eXoPlatform delivering enterprise social networks > me --verbose 4. w w w . c r a s h u b . o r g You can use @crashub or #crashub Try it online try.crashub.org/gists/ e61cb08d93746e576209 (pro tip follow @crashub) About this talk 5. w w w . c r a s h u b . o r g Once upon a time Why did I do that ? what is CRaSH 6. w w w . c r a s h u b . o r g Latest 1.2.9 / 1.3.0-cr5 Java 6+ / Groovy 1.7+ Base commands : jdbc, jmx, thread, jpa, log, etc.. Extensions: mail, cron CRaSH 7. w w w . c r a s h u b . o r g Modes Standalone / attach (download / brew / gvm) Embedded Connectors jvm (standalone & attach) ssh, telnet crash.js over websocket Concepts 8. w w w . c r a s h u b . o r g Standalone mode 9. w w w . c r a s h u b . o r g Return "hello world" Command script 10. w w w . c r a s h u b . o r g class helloworld { @Command String main() { return "Hello World" } } Command class 11. w w w . c r a s h u b . o r g class hello { @Command String world() { return "Hello World" } } Git style 12. w w w . c r a s h u b . o r g Command pipelining 13. w w w . c r a s h u b . o r g Write programs that do one thing and do it well. Write programs to work together. Write programs to handle text streams, because that is a universal interface. - Ken Thompson Unix philosophy 14. w w w . c r a s h u b . o r g % thread ls | thread dump | mail -s "something you should look at" julien@julienviet.com Pipeline example 15. w w w . c r a s h u b . o r g is a producer is a pipe is a pipe Pipeline example 16. w w w . c r a s h u b . o r g class daemon { @Command Pipe main() { [provide: {if (it.daemon) context.provide(it) }] as Pipe } } Pipe command 17. w w w . c r a s h u b . o r g # log ls -f org.crsh.* | log send -m "hello" # system propls | filter -p NAME:java.* | sort -f NAME # jmx query -p java.lang:type=GarbageCollector,name=* | jmx get -a Name -a CollectionCount -a CollectionTime Other examples 18. w w w . c r a s h u b . o r g Read Eval Print Loop aka REPL 19. w w w . c r a s h u b . o r g By default the script REPL parses CLI familiar for most CLI users Script REPL 20. w w w . c r a s h u b . o r g very much like groovysh evaluates Groovy expressions DSL for creating CLI compose pipes and closures New Groovy REPL since 1.3 21. w w w . c r a s h u b . o r g % (thread.ls | thread.dump | mail { S="something you should look at "admin@domain.com" })() Our command pipeline in Groovy 22. w w w . c r a s h u b . o r g More cool stuff 23. w w w . c r a s h u b . o r g Completers Renderers Keyboard: interruption / events Screen: streaming / styling More cool stuff 24. w w w . c r a s h u b . o r g Attach mode 25. w w w . c r a s h u b . o r g Embedding CRaSH 26. w w w . c r a s h u b . o r g Bootstrap: programmatic / Spring / Servlet Designed for embedding Lighweight : core jar about 600kb Modular : pay for what you need Virtual File System integration Embedding 27. w w w . c r a s h u b . o r g Ecosystem 28. w w w . c r a s h u b . o r g Created in Nov 2012 by Stephan Jaetzold Contributions by Burt Beckwith Recently updated to CRaSH 1.3 with additional features Grails Plugin 29. w w w . c r a s h u b . o r g And the story just begins 30. w w w . c r a s h u b . o r g Multi facet, powerful and extensible tool for all of us Join the community www.crashub.org @crashub crash-users@googlegroups.com Wrap up 31. w w w . c r a s h u b . o r g Extra slides 32. w w w . c r a s h u b . o r g new UIBuilder().table { header { label("key") label("value") } System.properties.each { k,v -> row { label(k).style(Color.red.fg()); label(v).style(Color.blue.fg()) } } } Building more complex UI with a DSL