Configuration Management - Finding the tool to fit your needs


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This presentation was originally given by Joseph Hall, SaltStack senior engineer, at the combined Montreal Python and DevOps Montreal meet up on April 14, 2014. Here is the talk abstract: In ye olde days of web, a company might manage a handful of servers, each manually and frequently tuned and re-tuned to the company's needs. Those days are gone. Server farms now dominate, and it is no longer reasonable to manage individual servers by hand. Various configuration management tools have stepped in to help the modern engineer, but which to choose? It is not an easy question, and canned pitches from sales people are unlikely to take into account all of your variables. This talk will attempt to discuss The Big Four objectively, and from what angles they approach the task at hand.

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Configuration Management - Finding the tool to fit your needs

  1. 1. Configuration Management Finding the tool to fit your needs
  2. 2. Disclosures and Caveats ● I’m biased (I work for SaltStack) ● Many of my views do not reflect SaltStack’s views ● I have only used Puppet and Salt ● All of the projects discussed are excellent, with talented teams behind them
  3. 3. Timeline: CFEngine ● Mark Burgess, 1993 ● Designed for automated configuration and management of large-scale computer systems ● Configuration and usage seen by many to be arcane ● Currently in third iteration (CFEngine 3)
  4. 4. Timeline: Puppet ● Luke Kanies, 2005 ● Unhappy with CFEngine 2, Luke built Puppet as a next-generation config management tool ● Designed to be easier to configure and use than CFEngine ● Uses a Ruby-like DSL
  5. 5. Timeline: Chef ● Adam Jacobs, 2009 ● Adam was unhappy with Puppet’s non- deterministic (by default) ordering ● Uses a very Ruby-like DSL ● Designed to mix ops with development ● “Infrastructure as code.”
  6. 6. Timeline: Salt ● Thomas Hatch, 2011 ● Originally designed for remote execution ● Config management added later ● Designed for speed, flexibility, ease of use, scale ● Based on data, not DSLs
  7. 7. Timeline: Ansible ● Michael DeHaan, 2012 ● Requires no agents on the remote machine, except for sshd ● Designed for ad hoc task execution and config managment ● Designed with simplicity in mind
  8. 8. Imperative vs Declarative ● Functional ● Do this, then this ● Chef ● Salt ● Ansible ● Object Oriented ● Do this and this, as you see fit ● Puppet ● Salt
  9. 9. Domain Specific Languages ● Designed for specific tasks ● Not generally useful for other tasks DSL ● Chef ● Puppet ● Salt No DSL ● Salt ● Ansible
  10. 10. Push vs Pull ● Server calls client ● Immediate remote execution ● Salt ● Ansible ● Client calls server ● Non-immediate remote execution ● Puppet ● Chef ● Salt
  11. 11. ● Puppet ● Chef ● Salt ● Ansible ● Salt ● Ansible Immediate Remote Execution Config Management
  12. 12. Remote Execution ● Use one machine to execute commands on another machine ● Config management is already a type of remote execution ● SSH (alone) is non-automated ● Queueing mechanisms are often used for remote execution
  13. 13. Puppet Example package: { “httpd”: ensure => “installed”, } service: { “httpd”: ensure => “running”, enable => true, require => Package[“httpd”], subscribe => File[“httpd”], } file: { “httpd”: path => “/etc/httpd/conf/httpd.conf”, content => template(“httpd/httpd.conf.erb”), #/etc/puppetlabs/puppet/modules/httpd/templates/httpd.conf.erb, require => Package[“httpd”], }
  14. 14. Chef Example package “httpd” template “httpd” do source “httpd.conf.erb” # stored in /templates/ in the current cookbook path “/etc/httpd/conf/httpd.conf” action :create end service “apache2” do action [:start, :enable] end
  15. 15. Salt Example httpd: pkg: - install service: - running - enable: True - requires: - file: httpd file: - managed - name: /etc/httpd/conf/httpd.conf - source: salt://httpd/httpd.conf # stored in /srv/salt/httpd/httpd.conf - requires: - pkg: httpd
  16. 16. Ansible Example - hosts: all tasks: - name: 1. Install Apache yum: name=httpd state=present - name: 2. Copy Apache Config template: src=httpd.conf.j2 dest=/etc/httpd/conf/httpd.conf - name: 3. Start Apache Service service: name=httpd state=running enabled=yes # httpd.conf is stored in the /templates/ directory for that role
  17. 17. Which one is for me? ● It depends ○ Do you have legacy CM code? ○ Do you need immediate remote execution? ○ Are you planning to use this layer programmatically? ○ Is a hybrid solution more appropriate for you? ○ Which one feels right?
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