Error Handling Done Differently
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@michaelneale www.CloudBees.com Monday, 13 June 2011
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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.
Transcript of Error Handling Done Differently
@michaelneale
www.CloudBees.com
Monday, 13 June 2011
Hosted build-time to Runtime - the full cycle
Monday, 13 June 2011
Monday, 13 June 2011
Tasty dog food
- we practice continuous deployment
- carefully...
(especially after that one time I...)
- bootstrapping !
Monday, 13 June 2011
Monday, 13 June 2011
CI in the cloud
- git push --> run tests, promote
- bees app:deploy
- BYO repo or use ours (even SVN ??)
Monday, 13 June 2011
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
Why a PaaS ?
- System administration challenged
- Make it someone else’s problem
- why not? just PLEASE think about lock in
Monday, 13 June 2011
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...
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Heaven to use
Hell to build **
Purgatory to manage **
** Not Your Problem.
Monday, 13 June 2011
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
But what I really want to talk quickly about ...
Monday, 13 June 2011
Exceptions. Errors.
What The Hell Is That Process Doing?
and how it relates to..
Monday, 13 June 2011
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.....
Monday, 13 June 2011
Exception handling is wrong...
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But it seems harmless...
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Monday, 13 June 2011
Monday, 13 June 2011
Erlang says no no no...
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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
FACT: Answer#3 will often work so well, you often don’t really spend time to think about #2**
** FibreError?
Monday, 13 June 2011
Imagine a programming environment:
- unlimited process spawning
- concurrency someone else’s problem
- don’t try to handle errors - let it fail
Monday, 13 June 2011
Erlang
Built for stability, and not bothering me.
Anything else is gravy.
Monday, 13 June 2011
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
...
nginx
supervisor
p1 p999
Erlang process
Example: My Host OS
haproxy
Each: own heap, garbage collector
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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
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 !
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We use them for
- Supervisory agents - controllers
- Autoscaling services (realtime data analytics)
- misc backend systems
- fun command line tools !
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Supervisor configuration
- Declare rules for restarting, failure
- So you don’t have to intervene !
- can hot reload changes
- can have dependent processes
Monday, 13 June 2011
Restart just busted process
Monday, 13 June 2011
Anyway, that is why we use Erlang, also...
- RabbitMQ
- Riak (nosql DB)
- CouchDB (nosql DB)
- Probably your telephone exchange
Monday, 13 June 2011
Thank you
Monday, 13 June 2011
