Big Picture
Version 2 (Anonymous, 03/13/2010 08:01 pm)
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| 2 | 1 | ||
| 3 | 1 | ## TracNav |
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| 4 | 1 | ||
| 5 | 1 | #### New To Puppet? |
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| 6 | 1 | ||
| 7 | 1 | - [[About Puppet]] |
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| 8 | 1 | - [[Puppet Compatibility]] |
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| 9 | 1 | - [[Whos Using Puppet]] |
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| 10 | 1 | - [[Getting Started]] |
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| 11 | 1 | - [[Puppet Best Practice]] |
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| 12 | 1 | - [[Downloading Puppet]] |
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| 13 | 1 | - [[Language Tutorial]] |
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| 14 | 1 | - [[Frequently Asked Questions]] |
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| 15 | 1 | - [[Documentation Start]] |
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| 16 | 1 | - [[Getting Help]] |
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| 17 | 1 | - [[Whos Using Puppet]] |
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| 18 | 1 | ||
| 19 | 1 | #### Release Notes |
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| 20 | 1 | ||
| 21 | 1 | - [[Glossary Of Terms]] |
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| 22 | 1 | - [[Style Guide]] |
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| 23 | 1 | - [[Puppet Recipes]] |
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| 24 | 1 | - [[Facter Recipes]] |
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| 25 | 1 | - [[Recipe Requests]] |
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| 26 | 1 | - [[Module Organisation]] |
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| 27 | 1 | - [[Puppet Modules]] |
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| 28 | 1 | - [[Puppet Executables]] |
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| 29 | 1 | - [[Puppet Internals]] |
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| 30 | 1 | ||
| 31 | 1 | #### References and Advanced Topics |
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| 32 | 1 | ||
| 33 | 1 | - [[Type Reference]] |
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| 34 | 1 | - [[Nagios Reference]] |
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| 35 | 1 | - [[Function Reference]] |
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| 36 | 1 | - [[Metaparameter Reference]] |
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| 37 | 1 | - [[Configuration Reference]] |
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| 38 | 1 | - [[Network Reference]] |
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| 39 | 1 | - [[Report Reference]] |
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| 40 | 1 | - [[Writing Your Own Functions]] |
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| 41 | 1 | - [[Parsing Architecture]] |
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| 42 | 1 | ||
| 43 | 1 | ||
| 44 | 1 | ||
| 45 | 1 | # Big picture |
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| 46 | 1 | ||
| 47 | 1 | Puppet is a **declarative language** for expressing system |
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| 48 | 1 | configuration, a **client and server** for distributing it, and a |
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| 49 | 1 | **library** for realizing the configuration. |
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| 50 | 1 | ||
| 51 | 1 | Rather than approaching server management by automating current |
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| 52 | 1 | techniques, Puppet reframes the problem by providing a language to |
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| 53 | 1 | express the relationships between servers, the services they |
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| 54 | 1 | provide, and the primitive objects that compose those services. |
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| 55 | 1 | Rather than handling the detail of how to achieve a certain |
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| 56 | 1 | configuration or provide a given service, Puppet users can simply |
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| 57 | 1 | express their desired configuration using the abstractions they're |
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| 58 | 1 | used to handling, like service and node, and Puppet is responsible |
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| 59 | 1 | for either achieving the configuration or providing the user enough |
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| 60 | 1 | information to fix any encountered problems. |
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| 61 | 1 | ||
| 62 | 1 | This document is a supplement to the [[Puppet Introduction]] and it |
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| 63 | 1 | is assumed that readers are familiar with the contents of that |
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| 64 | 1 | document. |
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| 65 | 1 | ||
| 66 | 1 | ## Less Detail, More Information |
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| 67 | 1 | ||
| 68 | 1 | A correct configuration must obviously provide the appropriate |
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| 69 | 1 | details, but a configuration tool should understand that the |
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| 70 | 1 | details are generally the easy part. The hard part of system |
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| 71 | 1 | configuration is understanding the complex relationships between |
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| 72 | 1 | services and the objects that comprise those services. One of the |
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| 73 | 1 | primary goals of Puppet is to allow users to push the details into |
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| 74 | 1 | lower levels of the configuration and pull the relationships into |
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| 75 | 1 | the foreground. |
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| 76 | 1 | ||
| 77 | 1 | For instance, take a typical Apache web server deployment. Puppet |
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| 78 | 1 | allows one to encapsulate all of the primitives necessary for |
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| 79 | 1 | successful deployment into one reusable object, and that object can |
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| 80 | 1 | even be abstracted to support multiple apache versions. Here's how |
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| 81 | 1 | a simple apache definition might look for a Debian server (Debian |
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| 82 | 1 | uses apache for 1.x versions and apache2 for 2.x versions): |
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| 83 | 1 | ||
| 84 | 1 | define apache(version, conf, user, group) { |
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| 85 | 1 | # abstract across apache1 and apache2 |
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| 86 | 1 | $name = $version ? { |
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| 87 | 1 | 1 => "apache", |
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| 88 | 1 | 2 => "apache2", |
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| 89 | 1 | } |
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| 90 | 1 | package{ $name: |
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| 91 | 1 | install => true, |
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| 92 | 1 | } |
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| 93 | 1 | ||
| 94 | 1 | file { "$conf": |
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| 95 | 1 | user => "$user", |
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| 96 | 1 | group => "$group", |
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| 97 | 1 | source => "$conf", |
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| 98 | 1 | } |
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| 99 | 1 | ||
| 100 | 1 | # we want the service to restart if the config file changes |
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| 101 | 1 | # or if the package gets upgraded |
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| 102 | 1 | service { "$name": |
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| 103 | 1 | running => true, |
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| 104 | 1 | subscribe => [file["$conf"], package["$name"]], |
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| 105 | 1 | } |
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| 106 | 1 | } |
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| 107 | 1 | ||
| 108 | 1 | Now, with this configuration, one can easily set multiple servers |
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| 109 | 1 | up to run different versions of apache. The key benefit here is |
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| 110 | 1 | that the information necessary to run apache correctly is separated |
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| 111 | 1 | from the decision to do so on a given host. For example: |
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| 112 | 1 | ||
| 113 | 1 | # import our apache definition file |
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| 114 | 1 | import "apache" |
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| 115 | 1 | ||
| 116 | 1 | node server1 { |
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| 117 | 1 | # use a locally-available config file |
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| 118 | 1 | apache { |
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| 119 | 1 | version => 1, |
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| 120 | 1 | conf => "/nfs/configs/apache/server1.conf", |
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| 121 | 1 | user => "www-data", |
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| 122 | 1 | group => "www-data", |
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| 123 | 1 | } |
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| 124 | 1 | } |
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| 125 | 1 | ||
| 126 | 1 | node server2 { |
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| 127 | 1 | # use a config that we pull from elsewhere |
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| 128 | 1 | apache { |
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| 129 | 1 | version => 2, |
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| 130 | 1 | conf => "http://configserver/configs/server2/httpd.conf" |
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| 131 | 1 | user => "www-data", |
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| 132 | 1 | group => "www-data", |
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| 133 | 1 | } |
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| 134 | 1 | } |
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| 135 | 1 | ||
| 136 | 1 | Notice that our node configuration only specifies 1) that a given |
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| 137 | 1 | server is running Apache, and 2) the information necessary to |
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| 138 | 1 | differentiate this instance of apache from another instance. If a |
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| 139 | 1 | given detail is going to be the same for all apache instances (such |
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| 140 | 1 | as the fact that the service should be running and that it should |
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| 141 | 1 | be restarted if the configuration file changes), then that detail |
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| 142 | 1 | does not have to be specified every time an Apache instance is |
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| 143 | 1 | configured. |
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| 144 | 1 | ||
| 145 | 1 | ## Describing Configuration |
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| 146 | 1 | ||
| 147 | 1 | Puppet's declarative language separates the "what" of the |
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| 148 | 1 | configuration from the "how". The "how" is pushed into the library, |
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| 149 | 1 | which generally provides the ability to manage a given entity on |
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| 150 | 1 | multiple platforms, isolating the Puppet user from platform |
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| 151 | 1 | details. |
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| 152 | 1 | ||
| 153 | 1 | **Language Example: Class Hierarchy Using Inherit** |
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| 154 | 1 | ||
| 155 | 1 | Inheritance can be used to override default values defined in base |
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| 156 | 1 | classes: |
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| 157 | 1 | ||
| 158 | 1 | class base { |
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| 159 | 1 | ||
| 160 | 1 | ||
| 161 | 1 | ||
| 162 | 1 | file { "/etc/sudoers": |
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| 163 | 1 | owner => "root", |
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| 164 | 1 | group => "root", |
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| 165 | 1 | mode => 440 |
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| 166 | 1 | } |
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| 167 | 1 | } |
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| 168 | 1 | ||
| 169 | 1 | # FreeBSD has a "wheel" group instead of a "root" group |
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| 170 | 1 | class freebsd inherits base { |
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| 171 | 1 | file [ "/etc/sudoers" ] { |
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| 172 | 1 | group => "wheel", |
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| 173 | 1 | } |
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| 174 | 1 | ||
| 175 | 1 | } |
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| 176 | 1 | ||
| 177 | 1 | ## Distributing Configuration |
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| 178 | 1 | ||
| 179 | 1 | The Puppet framework Library consists of a client and server. |
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| 180 | 1 | ||
| 181 | 1 | (picture/diagram: client, server, site-config -> host-config) |
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| 182 | 1 | ||
| 183 | 1 | A Puppet server is aware of the full configuration. As some |
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| 184 | 1 | component's configuration aspects depend on the configuration of |
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| 185 | 1 | other components (e.g. the firewall config includes the ports used |
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| 186 | 1 | by webservers), generating configuration for a component requires |
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| 187 | 1 | being aware of full configuration. |
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| 188 | 1 | ||
| 189 | 1 | A Puppet client that runs on a specific host (or perhaps the same |
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| 190 | 1 | host as its Puppet Server) is generally only concerned with the |
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| 191 | 1 | components to be configured on that host. |
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| 192 | 1 | ||
| 193 | 1 | Puppet Clients normally request or "pull" configuration from their |
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| 194 | 1 | server. The Server processes the configuration request for the host |
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| 195 | 1 | using a pre-generated tree model of the classes and definitions |
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| 196 | 1 | from the site-config. |
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| 197 | 1 | ||
| 198 | 1 | When configuration needs to be "pushed" to the clients, the Server |
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| 199 | 1 | can be asked to attempt to trigger each client to request "pull" a |
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| 200 | 1 | new host configuration. |
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| 201 | 1 | ||
| 202 | 1 | Example: Puppet server, library |
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| 203 | 1 | ||
| 204 | 1 | You can read more about the Puppet language in the [[Language |
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| 205 | 1 | Tutorial]] . |
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| 206 | 1 | ||
| 207 | 1 | ## Realizing the Configuration |
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| 208 | 1 | ||
| 209 | 1 | The Puppet Client Library contains the component knowledge of how |
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| 210 | 1 | to reach desired states and configurations for several objects: |
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| 211 | 1 | File, Package, etc. |
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| 212 | 1 | ||
| 213 | 1 | Example: Puppet Client, library: |
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| 214 | 1 | ||
| 215 | 1 | ...todo: file: transfer, mode, ownership... |
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| 216 | 1 | ||
| 217 | 1 | You can read more about the Puppet language in the [[Language |
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| 218 | 1 | Tutorial]] . |
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| 219 | 1 | ||
| 220 | 1 | Some components such as the webserver and firewall, from the |
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| 221 | 1 | simple-website example, require additional code to reach "closure". |
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| 222 | 1 | "Closure" is when the component is entirely responsible for |
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| 223 | 1 | implementing its own configuration. |
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| 224 | 1 | ||
| 225 | 1 | Much as database applications abstract the mechanics of storing, |
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| 226 | 1 | indexing, and searching their data, a component ideally should |
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| 227 | 1 | abstract the specifics of how to store, confirm, and implement its |
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| 228 | 1 | requested configuration. |