Building maintainable command-line tools with MRuby

MRuby and mruby-cli makes it possible to ship single binary command-line tools that can be used without setup effort. How can we make these easy to write too?

Transcript

1. Building maintainable command-line tools with MRuby
2. MRuby & mruby-cli Eric Hodel — @drbrain
3. About Me • Ruby commi?er • RubyGems commi?er • Rake commi?er • Author of many gems • On vacaEon
6. Fastly + Ruby www.ruby-lang.org rubygems.org
7. @FastlyJapan
8. Part Ⅰ
9. Web API Wrapper
10. Why not Ruby? • Install Ruby • Installing gems • Expensive support
11. MRuby =~ Ruby 1. Prototype in CRuby 2. Port to MRuby 3. Maintain in MRuby
12. MRuby
13. MRuby • Lightweight ruby • Embeddable • Hardware • SoWware
14. mrbgems • CRuby stdlib parts • mruby libraries • C extensions
15. Other mruby Talks 2016: Welcome to haconiwa 2016: Recent Advances in HTTP 2016: System calls hijacking with (m)ruby 2015: Making robot with mruby 2015: Building CLI Apps for Everyone 2014: MRuby as Development Plaborm for Payments 2014: MRuby on LEGO Mindstorms EV3 ® 2014: Resource Control Architecture scripEng with mruby
16. Using MRuby
17. build_config.rb • Which mrbgems to use • Which compiler to use • Library & include path • Can have many builds
18. mrbgem.rake • Gem metadata • Gem dependencies • Gem binaries
19. rake
20. rake Results • bin/your-cli • bin/mruby • bin/mirb • bin/mrbtest
21. mruby-cli
22. Building CLI Apps for Everyone
23. Write Ruby release on Linux, OS X, Windows
24. Using mruby-cli 1. Write MRuby 2. Compile 3. GOTO 1 unless tests pass 4. Release executables
25. MRuby Challenges
26. MRuby != CRuby
27. Modular stdlib • Minimal core library • mruby-array-ext • Easy to forget for mrbgems
28. Language Issues • No pre-defined globals • Some syntax bugs • No keyword arguments for def • Regexp replacements
29. ExcepEons • Inaccurate backtrace • More C exploraEon
30. PorEng Libraries • Easy overall • Beware restricted syntax • PorEng tests is hard
31. mrbgems • Like Ruby 1.6.x • Libraries have narrow focus • Expect to submit patches
32. Patches mruby-onig-regexp mruby-curl mruby-io mruby-h?psclient mruby-cli
33. Build InformaEon • Needed for cross-compile • Hard to read without rake
34. mruby-cli Challenges
35. Docker
36. Docker • Ready to cross-compile • Clumsy to use • Best opEon available
37. docker-compose run compile • Too long to type • run shell to debug • Unfamiliar environment
38. Build System
39. Task OrganizaEon • MRuby and mruby-cli mixed • Hard to add new tasks
40. Improvements • Build MRuby separately • Run docker from a task
41. Docker cd mruby; rake rake compile rake -f in-docker Outer Inner
42. "Outer" Tasks • Download MRuby • Global test setup • Release tasks
43. "Inner" Tasks • Cross-compile libraries • Compile MRuby • Run tests
44. AddiEonal Benefits • Hooks for custom tasks • Faster rake test
45. C Libraries
46. StaEc Linking • Single file • Re-release on vulnerabiliEes • Larger
47. Dynamic Linking • Easy vulnerability management • Adds a dependency
48. Cross Compiling
49. Cross Compiling • Download release • Cross-compile • MRuby compiler configuraEon
50. CrossLibrary CrossLibrary.new 'curl' do |cross| cross.release_name = 'curl-7.28.0' cross.url = "https://curl.haxx.se/…" # TODO: cross-compile OpenSSL too. cross.configure_flags << '--without-ssl' end
51. CrossLibrary CrossLibrary.new 'curl' do |cross| cross.release_name = 'curl-7.28.0' cross.url = "https://curl.haxx.se/…" # TODO: cross-compile OpenSSL too. cross.configure_flags << '--without-ssl' end
52. CrossLibrary CrossLibrary.new 'curl' do |cross| cross.release_name = 'curl-7.28.0' cross.url = "https://curl.haxx.se/…" # TODO: cross-compile OpenSSL too. cross.configure_flags << '--without-ssl' end
53. CrossLibrary CrossLibrary.new 'curl' do |cross| cross.release_name = 'curl-7.28.0' cross.url = "https://curl.haxx.se/…" # TODO: cross-compile OpenSSL too. cross.configure_flags << '--without-ssl' end
54. CrossLibrary CrossLibrary.new 'curl' do |cross| cross.release_name = 'curl-7.28.0' cross.url = "https://curl.haxx.se/…" # TODO: cross-compile OpenSSL too. cross.configure_flags << '--without-ssl' end
55. Part Ⅱ
56. Customer Support Tool
57. Problem • API-only to start • Complicated setup • Support burden
58. SoluEon • Automate • Validate inputs • Reduce errors
59. Prototypes
60. Single File Script • Easy to write • Inflexible
61. MulEple Scripts • One purpose per script • More flexible • Well documented
62. Extract classes • JSON-API • Argument parsing
63. Lessons
64. Document • No API docs • 50% comments • Users can suggest changes
65. Simple Scripts • Minimum dependencies • Minimum opEons • One script per task • Very few large scripts
66. Hard to Maintain • CRuby version • Clone and edit by support
67. Switch to mruby-cli
68. RubyGems Pa?ern • Subclass per subcommand • mruby-optparse • setup for opEons • execute to run
69. Example Command class ConditionList < Command def setup option_service_id required: true option_version required: true end
70. Example Command class ConditionList < Command def execute results = api.send_request … results.each do |result| puts "…" end end
71. mruby-optparse • Familiar • Type checking • Argument compleEon • Shell compleEon
72. mruby-curl • Most mature HTTP library • HTTP + HTTPS • Persistent connecEons • libcurl dependency
73. TesEng • mruby-mtest for asserEons • mruby-test as a runner • Test case setup is painful
74. TesEng
75. mruby-mtest • Like minitest • Test subclass • test_* methods • setup / teardown • Remember: MTest::Unit.new.run
76. mruby-test • Test runner • One MRuby VM per test file • Complete isolaEon
77. ComplicaEons • Global setup hard • docker-compose documentaEon • Slow startup
78. Workarounds • Setup before all tests • Pass data out-of-band • Compile only host for tesEng
79. rake bintest • IntegraEon tests • Assert output from input
80. Part Ⅲ
81. Future Work
82. mruby-cli • Improved build system • DocumentaEon • Easier upgrades
83. MRuby • Accurate backtraces • build_config.rb library • Keyword args in methods
84. CRuby • mrb_get_args() • AutomaEc type check • More expressive than rb_scan_args()
85. mruby-test • AutomaEc test_preload • --name opEon
86. Thank You QuesEons?