Lessons from Erlang

In this talk we will discuss thinking in a concurrent programming language along with the problems it has to solve. We will take a look at the real tools Erlang gives you to write highly-available systems that let you sleep through the night: dynamic tracing and remote REPL. We'll see how these tools are used.

Transcript

1. Lessons    From    Erlang Michał  Ślaski        @michalslaski   ! ! !      PolyConf,  Poznań,  31.10.2014
2. Erlang  timeline  and  my  background
3. Erlang  timeline  and  my  background Started  out  in  the  Ericsson  software  lab  1987  (!)
4. Erlang  timeline  and  my  background Started  out  in  the  Ericsson  software  lab  1987  (!) • I  was  six  years  old

5. Erlang  timeline  and  my  background Started  out  in  the  Ericsson  software  lab  1987  (!) • I  was  six  years  old
 Released  as  open  source  in  1998
6. Erlang  timeline  and  my  background Started  out  in  the  Ericsson  software  lab  1987  (!) • I  was  six  years  old
 Released  as  open  source  in  1998 • I  started  computer  science  at  AGH  2  years  later

7. Erlang  timeline  and  my  background Started  out  in  the  Ericsson  software  lab  1987  (!) • I  was  six  years  old
 Released  as  open  source  in  1998 • I  started  computer  science  at  AGH  2  years  later
 Gains  SMP  support  in  2005
8. Erlang  timeline  and  my  background Started  out  in  the  Ericsson  software  lab  1987  (!) • I  was  six  years  old
 Released  as  open  source  in  1998 • I  started  computer  science  at  AGH  2  years  later
 Gains  SMP  support  in  2005 • I  just  graduated  and  joined  Erlang  Solutions
9. Maintenance  vs.  Development
10. Maintenance  vs.  Development Maintenance  may  span  for  20  years,
 whereas  development  may  be  1-­‐2  years.     ! ! ! ! ! ! ! ! ! Schach,  R.,  Software  Engineering
 Fourth  Edition,  McGraw-­‐Hill,  Boston,  MA  1999

11. Erlang  properties
12. Erlang  properties OTP  behaviours   • set  of  design  patterns   • client-­‐server,  fsm,  supervisor   • application,  release

13. Erlang  properties OTP  behaviours   • set  of  design  patterns   • client-­‐server,  fsm,  supervisor   • application,  release
 What  for?   • consistent  maintenance  procedures   • one  tar  ball  artefact
14. Erlang  OTP  releases $ ls -l ../abacus.tar -rw-r--r-- 1 ms staff 12331520 Oct 31 12:01 abacus.tar ! $ ls -1 bin erts-6.1 lib releases ! $ ./bin/abacus Erlang/OTP 17 [erts-6.1] [smp:4:4] 
 [async-threads:10] [kernel-poll:false] ! Eshell V6.1 (abort with ^G) (abacus@127.0.0.1)1> github.com/michalslaski/erlang-­‐workshop
15. Erlang  properties
16. Erlang  properties Robustness   • simple  and  consistent  error  recovery   • supervision  hierarchies   • program  for  the  correct  case   • let  it  crash

17. Erlang  properties Robustness   • simple  and  consistent  error  recovery   • supervision  hierarchies   • program  for  the  correct  case   • let  it  crash
 What  for?   • resilient  to  bugs  and  failures
18. Erlang  properties  -­‐  supervision  tree
19. Erlang  properties  -­‐  supervision  tree
20. Erlang  properties  -­‐  supervision  tree
21. Erlang  properties  -­‐  supervision  tree supervisor
22. Erlang  properties  -­‐  supervision  tree supervisor worker
23. Erlang  properties  -­‐  supervision  tree supervisor worker
24. Erlang  properties  -­‐  supervision  tree supervisor worker
25. Erlang  properties  -­‐  supervision  tree supervisor worker
26. Erlang  properties
27. Erlang  properties Distribution   • explicit  or  transparent  distribution   • network-­‐aware  runtime  system

28. Erlang  properties Distribution   • explicit  or  transparent  distribution   • network-­‐aware  runtime  system
 What  for?   • remote  Erlang  shell  (REPL)   • remote  observing  tools
29. Erlang  properties  -­‐  distribution
30. Erlang  properties  -­‐  distribution cat
31. Erlang  properties  -­‐  distribution cat flea
32. Erlang  properties  -­‐  distribution cat flea nodes() = [cat@home, flea@home]
33. Erlang  properties  -­‐  distribution cat dog flea bird nodes() = [cat@home, flea@home]
34. Erlang  properties  -­‐  distribution cat dog flea bird nodes() = [cat@home, flea@home] nodes() = [dog@home, bird@home]
35. Erlang  properties  -­‐  distribution cat dog flea bird nodes() = [cat@home, flea@home] nodes() = [dog@home, bird@home]
36. Erlang  properties  -­‐  distribution cat dog flea bird nodes() = [cat@home, flea@home, dog@work, bird@work]
37. entop  vs.  top
38. entop  vs.  top
39. entop  vs.  top https://github.com/mazenharake/entop
40. Erlang  properties
41. Erlang  properties Hot  code  loading   • easily  change  code  in  a  running  system   • enables  non-­‐stop  operation   • simplifies  testing

42. Erlang  properties Hot  code  loading   • easily  change  code  in  a  running  system   • enables  non-­‐stop  operation   • simplifies  testing
 What  for?   • shorter  development  cycle   • non-­‐stop  operations
43. Erlang  properties
44. Erlang  properties Tracing  in  Erlang  VM   • Tracing  is  turned  on/off  per  process   • function  calls,  message  passing,  GC,  scheduler

45. Erlang  properties Tracing  in  Erlang  VM   • Tracing  is  turned  on/off  per  process   • function  calls,  message  passing,  GC,  scheduler
 What  for?   • live  debugging   • no  need  to  instrument  code  and  recompile
46. Erlang  tracing courtesy  of  Mats  Cronqvist
47. Erlang  tracing  calls
48. Erlang  tracing  calls redbug  -­‐  github.com/massemanet/eper   • tracing  tool  built  on  top  of  erlang:trace/3
49. Erlang  tracing  calls redbug  -­‐  github.com/massemanet/eper   • tracing  tool  built  on  top  of  erlang:trace/3 1> redbug:start("lists:seq(X,Y) -> return"). {30,1}! 2> lists:seq(1,5).! [1,2,3,4,5]! ! % 12:32:17 <0.32.0>({erlang,apply,2})! % lists:seq(1, 5)! ! % 12:32:17 <0.32.0>({erlang,apply,2})! % lists:seq/2 -> [1,2,3,4,5]
50. Flame  Graphs  for  Erlang  -­‐  eflame
51. Flame  Graphs  for  Erlang  -­‐  eflame github.com/proger/eflame   • as  stacks  are  collected  through  tracing,
 blocking  calls  are  noticed  and  are  drawn  in  blue
52. Flame  Graphs  for  Erlang  -­‐  eflame github.com/proger/eflame   • as  stacks  are  collected  through  tracing,
 blocking  calls  are  noticed  and  are  drawn  in  blue
53. What’s  next?
54. Erlang  the  Movie
55. Erlang  the  Movie
56. Erlang  the  Movie  II
57. Erlang  the  Movie  II
58. Open  source  projects
59. Open  source  projects • RabbitMQ  message  broker  

60. Open  source  projects • RabbitMQ  message  broker  
 • MongooseIM  XMPP  server

61. Open  source  projects • RabbitMQ  message  broker  
 • MongooseIM  XMPP  server
 • Riak  database

62. Open  source  projects • RabbitMQ  message  broker  
 • MongooseIM  XMPP  server
 • Riak  database
 • CouchDB  database
63. Erlang  Community
64. Erlang  Community Erlang  Central   • www.erlangcentral.org

65. Erlang  Community Erlang  Central   • www.erlangcentral.org
 Erlang  Factory   • Berlin,  December  4   • San  Francisco,  March  26-­‐27

66. Erlang  Community Erlang  Central   • www.erlangcentral.org
 Erlang  Factory   • Berlin,  December  4   • San  Francisco,  March  26-­‐27
 Lambda  Days   • Kraków,  February  26-­‐27
67. Lambda  Days  Call  for  Papers
68. Lambda  Days  Call  for  Papers SUBMIT  YOUR  TALK
69. Questions? ! Michał  Ślaski          @michalslaski