CFEngine 3

CFEngine 3

Code Freeze 2012
Jan 12, 2012
Brian Repko
http://www.learnthinkcode.com
Copyright 2011 LearnThinkCode, Inc.
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License

Agenda
●
Introduction to CFEngine
●
What it is
●
How it works
●
Examples
●
New Machine Setup
●
CFEngine vs Chef vs Puppet


IANAS (sysadmin)
●
My role has been as a developer / architect
working with sysadmins to deploy our
applications
●
When automated, we have used cfengine
●
This presentation will use cfengine
configuration from Entagen (triplemap.com)
for our examples
●
Thanks to Frans Lawaetz!


CFEngine
● Systems Maintenance Tool
● Configures and automates large-scale IT infrastructure
● Ensures the availability, security and compliance of systems and
applications
● Created by Mark Burgess (Ph.D in Theoretical Physics)
● CFEngine 1 – released in 1993 (at Oslo University / post-doc)
● CFEngine 2 – released in 1998 (Computer Immunology)
● CFEngine 3 – released in 2008 (Promise Theory)
● Two editions – Community (FOSS) and Nova (commercial)
● Nova has portal, reporting, native MS Mac/Windows mgmt, high-
availability, virtualization, KM, commercial support
● Written in C, runs on all types of systems including mobile, tablet
and embedded systems
● Tons of low-level functions and action configurations to reuse

Who uses it


Components
● cf-execd
● Cron-like lightweight daemon that runs cf-agent (default is every 5 minutes)
● More sophisticated than cron (randomness, fail-safe operation, time exclusions)
● cf-agent
● The main component that does the system automation and maintenance (maintaining promises)
● Runs cf-promises (another executable) to validate bundles/promise syntax
● cf-serverd
● Distributes policy and data files (cf-agent pulls from cf-serverd)
● Hubs (Nova only), Servers and Clients
● Can run standalone as well
● All systems run the same configuration policies (Hubs/Servers are Clients too!)
● Top-level system(s) get their files from version control (please say yes)
● Promises (statements)
● Describes the desired state of some aspect of a system (file, process, package...)
● Bundles (collections of promises, aka policies)
● promises.cf as bootstrap policy – says what other bundles to execute
● Variables and Classes (CFEngine defined and User defined)
● Classes are booleans that allow control over which promises are executed and when


Bundles
● Bundles are typically designed to target a particular set of systems
and/or a particular objective
● Bundles have a type (which executable) and name
● “common” is for all executables
● Each bundle type has a control (configuration) promise body
● Each bundle is run three times in order to get each promise fulfilled
(convergence)
● Bundles have sections (“promise type”) whose order is fixed based
on the executable
● promises.cf, failsafe.cf and update.cf are “standard”
● cfengine_stdlib.cf has lots of the low level functionality
● The “common control body” specifies the files to process and the
bundle sequence – specified in promises.cf (or standalone files)


Bundles
● Bundle promise type order (for agent)
● vars – define variables
● classes – define classes
● outputs – (Nova) data collection
● interfaces – network interfaces
● files – files and file contents
● packages – packages / libraries to install / uninstall
● environments – (Nova) virtualization
● methods – process other bundles
● processes – processes that should / should not be running
● services – collections of processes
● commands – commands to execute
● storage – disks and filesystems
● databases – (Nova) LDAP, SQL and Windows Registry
● reports – reporting on cfengine state


Variables and Classes
● Variables
● Special Variables (CFEngine defined)
● Scalar types - string, int, real
● List types - slist, ilist, rlist
● Scalar expression ${var}, List expression @{var}
● Scalar expression of a list is a loop / for-each
● Classes
● Booleans that guard promises
● CFEngine-defined (aka hard) Classes
● User-defined (aka soft) Classes
● Often set by using built-in functions
● Can also be defined by promise repair or failure
● Combined with not ('!'), and ('.' or '&'), or ('|' or '||')

Promises
● Within its promise type
class-expression::
“promiser” [→ {“promisee1”,...}]
attr1 => value1,
attr2 => value2, ...
attrN => valueN;
● Promisee is only used by Nova
● Promise body is all the attributes
● Promise body may reference body-parts
● Many common attributes, others based on type

Promises
● File promise – edit_line bundle
● Ability to handle file edits
● Templates or line changes
● Promise Body Parts
● Reusable setup of promise attributes
● Can take parameters / variables
● Can use classes internally
● Functions
● Lots of built-in functions
● Many functions return a class (boolean)

Example 1 – Java Setup
●
Review tm-java.cf (a portion of tm.cf)
●
Goal is to have Oracle Java (JDK) as java
●
No RHEL repo for it


Example 2 – DB, Tomcat, HTTP
●
Review tm-server.cf
●
All install as packages
●
All run as services
●
Configuration and setup
●
Httpd configuration as template
●
Restart httpd if configuration changed
●
Tomcat to run as non-root user
●
Tomcat context copied in
●
MySQL db creation as idempotent(?)

Example 3 – Web App Deploy
● Review tm-webapps.cf
● Web applications are built with Jenkins
● Jenkins jobs configure which hosts get which builds
● Save war with .<host> appended to name
● CFEngine needs to know when to pick up the wars
(and not catch them in the middle)
● Trigger file with <host> name
● Some applications require special files
● And then unzip everything and restart Tomcat


New Machine Setup
● Review Entagen Triplemap Demo script
● Quick script to bootstrap Triplemap Demos
● Builds <x>.triplemap.com
● Machine setup with KVM
● Some VM support in Nova (I've not seen it)
● Have seen knife (Chef) used to bring up
CFEngine policy servers and clients
● And then CFEngine to setup Puppet
● And then Puppet to setup Chef
● http://blog.afistfulofservers.net/

Challenges to CFEngine
● Learning Curve
● Syntax and flow in general
● No “standard style”
● Global vs Local on variables / classes
● Reserved names
● Timing / Locks
● Large Ecosystem
● Tons of variables, classes, functions
● Start small! Collaborate!
● Code review files in VCS!
● Be careful – you are root everywhere at once!
● cf-promises will verify syntax – it will not prevent stupid – test your files!
● Use test.cf and limit its execution
● Run on a virtual machine
● Run your tests at least twice on a given machine


CFEngine vs Chef vs Puppet
● Chef and Puppet are both Ruby-based
● CFEngine is C
● Runs on anything (Nova) and is fast and lightweight (memory footprint)
● CFEngine scales very well (AMD running 10k clients per server)
● Commercial support available for all
● Is “only in Nova” driving people away from CFEngine?
● Execution repairs itself (failsafe/update) – don't know for Chef/Puppet
● CFEngine language is “odd” - learning curve for all
● CFEngine file editing capabilities seem strong (lots of body parts in stdlib)
● CFEngine will be more verbose
● but everything is available and easily tweakable (vs “Puppet defines the how”)
● to an extent...promise types are written in C
● CFEngine based on heuristics / Promise Theory vs Graph / Dependencies / Model
● Lots of sharing of Chef recipes and Puppet scripts – not so much with CFEngine
● Community Open Promise Body Library but that's it...
● Puppet a reaction to CFEngine 2 (Luke Kanies) – CFEngine 3 is a rewrite
● Chef a reaction to Puppet


References
●
CFEngine
●
http://cfengine.com/getting-started
●
Vertical SysAdmin (Aleksey)
●
http://www.verticalsysadmin.com/blog
●
http://www.verticalsysadmin.com/cfengine/
Getting_Started_with_CFEngine_3.pdf
●
Sample WordPress setup
●
http://sysadvent.blogspot.com/2011/12/da
y-15-automating-wordpress-with.html


Q/A – Thank You!


CFEngine 3

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