Architect Michael Neale expounds on errors, exceptions, Erlang, and how we do things at CloudBees. Bonus topic: the joys of Platform as a Service. Originally presented at Sydney YOW! night - Jun 14, 2011.

1. @michaelneale
www.CloudBees.com
Monday, 13 June 2011

2. Hosted build-time to Runtime - the full cycle
Monday, 13 June 2011

3. Monday, 13 June 2011

4. Tasty dog food
- we practice continuous deployment
- carefully...
(especially after that one time I...)
- bootstrapping !
Monday, 13 June 2011

5. Monday, 13 June 2011

6. CI in the cloud
- git push --> run tests, promote
- bees app:deploy
- BYO repo or use ours (even SVN ??)
Monday, 13 June 2011

7. Anyway... you can use it free
- signup www.cloudbees.com
- free FOSS Jenkins CI hosting
- free general Apps hosting
- “public cloud” or private edition (hybrid?)
- thousands of apps hosted already
Monday, 13 June 2011

8. Why a PaaS ?
- System administration challenged
- Make it someone else’s problem
- why not? just PLEASE think about lock in
Monday, 13 June 2011

9. My experience
- fell in love with GAE, force.com
- terrified of any and all lock in at the time
- had nothing better to do ... so cloudbees...
Monday, 13 June 2011

10. Heaven to use
Hell to build **
Purgatory to manage **
** Not Your Problem.
Monday, 13 June 2011

11. Some things we use to get it done:
- scala (back end apps)
- ruby (chef, rails, proxymachine, lots)
- java (jenkins and plugins)
- erlang (“agents” and lots more..)
Monday, 13 June 2011

12. But what I really want to talk quickly about ...
Monday, 13 June 2011

13. Exceptions. Errors.
What The Hell Is That Process Doing?
and how it relates to..
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14. Keeping things running without falling into a
weeping trembling mess in the corner every time
you hear an SMS sound or a phone ring or an
email chime etc etc etc.....
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15. Exception handling is wrong...
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16. But it seems harmless...
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18. Monday, 13 June 2011

19. Erlang says no no no...
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20. Question: a process on server not responding
Answer:
1) panic
2) take time thinking about underlying cause
3) bounce the bastard and pray **
Monday, 13 June 2011

21. FACT: Answer#3 will often work so well, you
often don’t really spend time to think about #2**
** FibreError?
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22. Imagine a programming environment:
- unlimited process spawning
- concurrency someone else’s problem
- don’t try to handle errors - let it fail
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23. Erlang
Built for stability, and not bothering me.
Anything else is gravy.
Monday, 13 June 2011

24. Process isolation
- it works so well
- nothing shared
- has worked so well for so long with OSes
- in erlang - each ‘process’ is like a process !
Monday, 13 June 2011

25. nginx Example: My Host OS
haproxy Erlang process
supervisor
...
p1 p999
Each: own heap, garbage collector
Monday, 13 June 2011

26. Erlang processes, like OS processes
- Can only send messages to each other
- Can fail independently
- Can be restarted, safely
- Easy to write apps for - Old School !
Monday, 13 June 2011

27. Better
- Tiny overhead (can have 100K+ of them !)
- perfect for supervisory agents
- distribute: run on every box if you like !
- lots of processes == lots of concurrency
- if you need to block, block !
Monday, 13 June 2011

28. We use them for
- Supervisory agents - controllers
- Autoscaling services (realtime data analytics)
- misc backend systems
- fun command line tools !
Monday, 13 June 2011

29. Supervisor configuration
- Declare rules for restarting, failure
- So you don’t have to intervene !
- can hot reload changes
- can have dependent processes
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30. Restart just busted process
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31. Anyway, that is why we use Erlang, also...
- RabbitMQ
- Riak (nosql DB)
- CouchDB (nosql DB)
- Probably your telephone exchange
Monday, 13 June 2011

32. Thank you
Monday, 13 June 2011