Puppet Camp Sydney 2015: The (Im)perfect Puppet Module
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This document summarizes a Puppet module training session. It discusses common patterns for Puppet modules, including using parameters and classes, and avoiding common pitfalls like direct Hiera lookups and overly broad module scopes. The training provides guidance on file structure, style guidelines, and best practices for creating reusable, testable Puppet modules. It also includes an example walk-through of the puppetlabs-ntp module on GitHub.
![12PITFALL #1: Hunting for Hiera lookups
class
nginx::params
{
$worker_processes
=
$::processorcount
$worker_connections
=
‘1024’
$conf_template
=
‘nginx/nginx.conf.erb’
$error_pages_default
=
false
$set_real_ip
=
hiera(“nginx::real_ip_range”)
$real_ip_header
=
‘X-‐Forwarded-‐For’
$blocked_ips
=
[]
$certs
=
{}
$server_template
=
'nginx/server-‐template.conf.erb’
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Puppet Camp Sydney 2015: The (Im)perfect Puppet Module
- 1. Puppet Camp Sydney The (im)perfect Puppet module
- 2. 2AGENDA Who we are The common pattern Pitfalls Module standards Module walk-through‘
- 3. WHO IS ODECEE? Innovation for the Enterprise A digital world where technology is simple and business gets what it wants 170+ staff Banking/financial services Communications Logistics Insurance Government Offices in Melbourne & Sydney Digital DevOps Sprout is designed to collaborate on new ideas and develop innovative ‘real world’ solutions.
- 4. 4WHO WE ARE PHILIP JAYPETER HALL • Ten years industry experience • Odecee Lead Engineer • Swinburne University Centre for Astrophysics & Supercomputing • realestate.com.au • catchoftheday.com.au @peterkh • Eight years industry experience • Odecee Senior Engineer • Ericsson Mobile Packet Core • Softel Systems • Puppet certified professional #454 @ps_jay
- 5. 5 Data SCOPE Business logic goes here (not sharable) Node Role Profile No business logic Sharable on the Puppet Forge Class Module Hiera Explicit Hiera lookups Automatic lookups only Scope of our talk
- 6. 6 Style guide: • v1.1.2: Existed 2011 – 2015 • v2.0.1: Current 2015 onwards Guiding principles: • Readability matters • Scoping and simplicity are key • Your module is a piece of software Covers writing code but not how to structure modules CODE STANDARDS docs.puppetlabs.com/guides/style_guide.html
- 7. 7MODULE STANDARDS Two documents • Module fundamentals: covers file-system layout docs.puppetlabs.com/puppet/latest/reference/modules_fundamentals.html • Beginners guide to modules: step-by-step guide docs.puppetlabs.com/guides/module_guides/bgtm.html
- 8. 8 > puppet module generate pcsyd15-‐foo pcsyd15-‐foo/Gemfile pcsyd15-‐foo/metadata.json pcsyd15-‐foo/Rakefile pcsyd15-‐foo/README.md pcsyd15-‐foo/manifests/init.pp pcsyd15-‐foo/spec/spec_helper.rb pcsyd15-‐foo/spec/classes/init_spec.rb pcsyd15-‐foo/tests/init.pp MODULE SKELETON
- 9. 9AUTOMATIC PARAMETER LOOKUP Puppet 3 – automatic lookup class foo ( param_1, # no default param_2 = “a default”, ) Since puppet 3, parameters get their value automatically Explicitly set in a resource-like declaration Hiera lookup (automatic) Default provided by class If no default, catalog compile fails Equivalent Puppet 2 code class foo ( param_1 = hiera(“foo::param_1”), param_2 = hiera(“foo::param_2”, “a default”) )
- 10. 10THE COMMON MODULE PATTERN params.pp • Defaults • Handle operating system differences init.pp • Inherit from params.pp • Contain (or anchor) other subclasses (install, config, …) Hiera config.pp, install.pp, etc. • Inherit from init.pp • Contained by init.pp init.pp variables referenced by all other classes/defines puppet-stdlib used for param validation Well known Puppet Forge contributors following this pattern: • puppetlabs • example42 • garethr
- 11. 11PITFALL #1: Looking up Hiera directly • Module less sharable: not all installations use Hiera • Harder to debug: more areas of code to identify Hiera lookups • Non-obvious: Module user needs to know all “magic” Hiera values to set for desired outcome • Complex unit testing: Need to feed Hiera values as well as parameters
- 12. 12PITFALL #1: Hunting for Hiera lookups class nginx::params { $worker_processes = $::processorcount $worker_connections = ‘1024’ $conf_template = ‘nginx/nginx.conf.erb’ $error_pages_default = false $set_real_ip = hiera(“nginx::real_ip_range”) $real_ip_header = ‘X-‐Forwarded-‐For’ $blocked_ips = [] $certs = {} $server_template = 'nginx/server-‐template.conf.erb’ ...
- 13. 13PITFALL #2: Module Scope • A module should only have one area of responsibility • That module should be the only module with that area of responsibility • Anti-pattern: • Apache module for installing httpd • MyPHPApp module installs a vhost config in: /etc/httpd/conf.d/
- 14. 14PITFALL #3: Dependencies • Don’t have “too many” dependencies • puppet-stdlib is okay & expected • Aim for zero dependencies • Testing is more complex: need to include the dependency • Module less sharable: now dependent on additional classes that others may not have • From Module Fundamentals: “Be wary of having classes declare classes from other modules”
- 15. 15 Example of a class including a class: # Class for creating the PuppetDB postgresql database class puppetdb::database::postgresql( … ) inherits puppetdb::params { … # create the puppetdb database postgresql::server::db { $database_name: … } } Must also have puppetlabs-postgresql module Alternatively: • Document in the README and then link in a “profile” class • Create module parameter for inclusion of the external class PITFALL #3: puppetlabs-puppetdb
- 17. CONSIDERATIONS Anchor pattern or contain function needed for classes inside classes Hiera needed to keep profiles and roles sensible Puppet version > 2.6.2 needed for param inherits
- 18. 18 Separation between modules keeps testing simple Common patterns reduces staff ramp up time Mix puppet forge and local modules with ease IN SUMMARY
- 19. Questions? @odecee www.facebook.com/odeceesocialwww.odecee.com.au www.linkedin.com/company/odecee Philip JayPeter Hall Lead DevOps engineer @peterkh @ps_jay Senior DevOps Engineer