Customizing Chef

For Fun and Profit

@jonlives

Jon Cowie

Sr Operations Engineer

@jonlives

@jonlives

@jonlives

Beginning of 2010 Today

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Chef at Etsy

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Chef at Etsy

• Open Source Chef Server

• ~1500 Nodes

• CentOS, some Mac OS X

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We Love Chef!

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We Know Best.

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Absorb what is useful.

Discard what is useless.

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“I am not smart enough to build an ontology … that

can encompass all the variations in infrastructure.

Nobody is, the world moves too fast.”

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There is no magic pill.

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You are the expert.

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Customizability

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Thin Server

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Thick Client

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Get Config Data / Initialize

• Load client.rb

• Server URL

• Auth Credentials

• Paths

• Run ohai

• Collect attributes

• Plugins!

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Ohai Plugins• Add attributes to your

node • Executed at start of

run • Single Ruby file • Highest precedence

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Ohai Plugins - v6

provides ‘awesome’ !

awesome Mash.new awesome[:sauce] = "Sricacha" awesome[:level] = "11"

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Ohai Plugins - v7 (Coming soon!)Ohai.plugin(:Awesome) do provides "awesome" collect_data(:darwin) do awesome Mash.new awesome[:sauce] = “Sriracha" awesome[:level] = 11 end end

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Ohai Plugins - client.rb / solo.rb

Ohai::Config[:plugin_path] << /<path>/plugins

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Authenticate / Register

• Authenticate to Server

• <clientkey>.pem

• Register if not already registered

• <validation>.pem

• If both fail, go directly to jail.

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Load / Build Node

• Download node

• Combine attributes

• Expand run_list

• Order matters!

• Create RunStatus object

• Run start handlers

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Handlers

• Respond to specific situations

• Start, Report, Exception • Common Code

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Handlers - Common Coderequire "chef/handler" !

class HandlerName < Chef::Handler def report # Ruby code goes here end end

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Handlers - client.rb / solo.rb

require “/path_to/mystarthandler.rb" !

my_start_handler = MyStartHandler.new !

start_handlers << my_start_handler

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Synchronize Cookbooks

• Get cookbook files list

• Only required recipes, files & templates

• Compares to local cache

• Download changes

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Set up RunContext

• Cookbook Collection

• Definitions List

• Events

• Notifications

• Node

• Resource Collection

• Empty for now…

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Events• Respond to interesting

events • Pub / Sub model • EventDispatch::Base • Formatter • Custom Subscriber

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Events - Custom Subscriberrequire “chef/event_dispatch/base" !

class AwesomeSubscriber < Chef::EventDispatch::Base def run_started(run_status) … end # Method for each interesting event end

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Events - Register Subscriberrequire "chef/handler" require “/path/awesome_subscriber.rb' !

class AwesomeSubscriberStartHandler < Chef::Handler def report event_dispatcher_subscriber = AwesomeSubscriber.new @run_status.events.register(event_dispatcher_subscriber) end end

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Load Cookbook Data

• Populate Resource Collection

• Libraries

• Attributes

• Resources / Providers

• Definitions

• Recipes

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Converge Node

• Actually changes node

• Apply resource collection

• Again, order matters!

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Finalize

• Successful Run

• Save Node

• Report Handlers

• Failed Run

• Exception Handlers

• 💩

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Report & Exception Handlersdef report if @run_status.success? # Do a happy dance elsif @run_status.failed? # Sad panda. end end

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Handlers - client.rb / solo.rbrequire “/var/chef/handlers/mystarthandler.rb"

require "/var/chef/handlers/mynewhandler.rb"

!

my_start_handler = MyStartHandler.new

my_new_handler = MyNewHandler.new

!

start_handlers << my_start_handler

report_handlers << my_new_handler

exception_handlers << my_new_handler

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That RunStatus Object Again…• Accessible to handlers

• Run status & timings

• Exception and Backtrace

• All & updated resources

• RunContext

• Node object

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Don’t fear the code!• https://github.com/opscode/chef

• lib/chef/handler.rb

• lib/chef/run_status.rb

• lib/chef/run_context.rb

• lib/chef/event_dispatch/base.rb

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Um…wat?

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Criteria for Customization

Simplicity

Modularity

Visibility

Maintainability

Scalability

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November 2014 !

http://jonliv.es/book !

O’Reilly Stand

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Thanks! Questions?

!

Office Hours @ 3.15, Marina Room @jonlives / http://jonliv.es / jcowie@etsy.com