Error Handling Done Differently

@michaelneale www.CloudBees.comMonday, 13 June 2011

Hosted build-time to Runtime - the full cycleMonday, 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

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 alreadyMonday, 13 June 2011

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

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...Monday, 13 June 2011

But it seems harmless...Monday, 13 June 2011

Erlang says no no no...Monday, 13 June 2011

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 failMonday, 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 Example: My Host OS haproxy Erlang process supervisor ... p1 p999 Each: own heap, garbage collectorMonday, 13 June 2011

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 !Monday, 13 June 2011

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

Supervisor conﬁguration - Declare rules for restarting, failure - So you don’t have to intervene ! - can hot reload changes - can have dependent processesMonday, 13 June 2011

Restart just busted processMonday, 13 June 2011

Anyway, that is why we use Erlang, also... - RabbitMQ - Riak (nosql DB) - CouchDB (nosql DB) - Probably your telephone exchangeMonday, 13 June 2011

Thank youMonday, 13 June 2011

Error Handling Done Differently

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