chef_gem

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Warning

The chef_gem and gem_package resources are both used to install Ruby gems. For any machine on which the chef-client is installed, there are two instances of Ruby. One is the standard, system-wide instance of Ruby and the other is a dedicated instance that is available only to the chef-client. Use the chef_gem resource to install gems into the instance of Ruby that is dedicated to the chef-client. Use the gem_package resource to install all other gems (i.e. install gems system-wide).

Use the chef_gem resource to install a gem only for the instance of Ruby that is dedicated to the chef-client. When a gem is installed from a local file, it must be added to the node using the remote_file or cookbook_file resources.

The chef_gem resource works with all of the same properties and options as the gem_package resource, but does not accept the gem_binary property because it always uses the CurrentGemEnvironment under which the chef-client is running. In addition to performing actions similar to the gem_package resource, the chef_gem resource does the following:

  • Runs its actions immediately, before convergence, allowing a gem to be used in a recipe immediately after it is installed
  • Runs Gem.clear_paths after the action, ensuring that gem is aware of changes so that it can be required immediately after it is installed

Syntax

A chef_gem resource block manages a package on a node, typically by installing it. The simplest use of the chef_gem resource is:

chef_gem 'package_name'

which will install the named gem using all of the default options and the default action (:install).

The full syntax for all of the properties that are available to the chef_gem resource is:

chef_gem 'name' do
  clear_sources              TrueClass, FalseClass
  compile_time               TrueClass, FalseClass
  notifies                   # see description
  options                    String
  package_name               String # defaults to 'name' if not specified
  provider                   Chef::Provider::Package::Rubygems
  source                     String
  subscribes                 # see description
  timeout                    String, Integer
  version                    String
  action                     Symbol # defaults to :install if not specified
end

where

  • chef_gem tells the chef-client to manage a gem
  • 'name' is the name of the gem
  • action identifies which steps the chef-client will take to bring the node into the desired state
  • clear_sources, compile_time, options, package_name, provider, source, timeout, and version are properties of this resource, with the Ruby type shown. See “Properties” section below for more information about all of the properties that may be used with this resource.

Actions

This resource has the following actions:

:install
Default. Install a gem. If a version is specified, install the specified version of the gem.
:nothing
Define this resource block to do nothing until notified by another resource to take action. When this resource is notified, this resource block is either run immediately or it is queued up to be run at the end of the chef-client run.
:purge
Purge a gem. This action typically removes the configuration files as well as the gem.
:reconfig
Reconfigure a gem. This action requires a response file.
:remove
Remove a gem.
:upgrade
Install a gem and/or ensure that a gem is the latest version.

Properties

This resource has the following properties:

clear_sources

Ruby Types: TrueClass, FalseClass

Set to true to download a gem from the path specified by the source property (and not from RubyGems). Default value: false.

Note

Another approach is to use the gem_package resource, and then specify the gem_binary location to the RubyGems directory that is used by Chef. For example:

gem_package 'gem_name' do
  gem_binary Chef::Util::PathHelper.join(Chef::Config.embedded_dir,'bin','gem')
  action :install
end

New in Chef Client 12.3.

compile_time

Ruby Types: TrueClass, FalseClass

Controls the phase during which a gem is installed on a node. Set to true to install a gem while the resource collection is being built (the “compile phase”). Set to false to install a gem while the chef-client is configuring the node (the “converge phase”). Possible values: nil (for verbose warnings), true (to warn once per chef-client run), or false (to remove all warnings). Recommended value: false.

To suppress warnings for cookbooks authored prior to chef-client 12.1, use a respond_to? check to ensure backward compatibility. For example:

chef_gem 'aws-sdk' do
  compile_time false if respond_to?(:compile_time)
end

Warning

If you are using chef-sugar—a community cookbook—it must be version 3.0.1 (or higher) to use the previous example. If you are using an older version of chef-sugar, the following workaround is required:

chef_gem 'gem_name' do
  compile_time true if Chef::Resource::ChefGem.instance_methods(false).include?(:compile_time)
end

See this blog post for more background on this behavior.

New in Chef Client 12.1.

ignore_failure

Ruby Types: TrueClass, FalseClass

Continue running a recipe if a resource fails for any reason. Default value: false.

notifies

Ruby Type: Symbol, ‘Chef::Resource[String]’

A resource may notify another resource to take action when its state changes. Specify a 'resource[name]', the :action that resource should take, and then the :timer for that action. A resource may notifiy more than one resource; use a notifies statement for each resource to be notified.

A timer specifies the point during the chef-client run at which a notification is run. The following timers are available:

:before
Specifies that the action on a notified resource should be run before processing the resource block in which the notification is located.
:delayed
Default. Specifies that a notification should be queued up, and then executed at the very end of the chef-client run.
:immediate, :immediately
Specifies that a notification should be run immediately, per resource notified.

The syntax for notifies is:

notifies :action, 'resource[name]', :timer
options

Ruby Type: String

One (or more) additional options that are passed to the command.

package_name

Ruby Types: String

The name of the gem. Default value: the name of the resource block See “Syntax” section above for more information.

provider

Ruby Type: Chef Class

Optional. Explicitly specifies a provider. See “Providers” section below for more information.

retries

Ruby Type: Integer

The number of times to catch exceptions and retry the resource. Default value: 0.

retry_delay

Ruby Type: Integer

The retry delay (in seconds). Default value: 2.

source

Ruby Type: String

Optional. The path to a gem in the local file system.

subscribes

Ruby Type: Symbol, ‘Chef::Resource[String]’

A resource may listen to another resource, and then take action if the state of the resource being listened to changes. Specify a 'resource[name]', the :action to be taken, and then the :timer for that action.

A timer specifies the point during the chef-client run at which a notification is run. The following timers are available:

:before
Specifies that the action on a notified resource should be run before processing the resource block in which the notification is located.
:delayed
Default. Specifies that a notification should be queued up, and then executed at the very end of the chef-client run.
:immediate, :immediately
Specifies that a notification should be run immediately, per resource notified.

The syntax for subscribes is:

subscribes :action, 'resource[name]', :timer
timeout

Ruby Types: String, Integer

The amount of time (in seconds) to wait before timing out.

version

Ruby Types: String

The version of a gem to be installed or upgraded.

Providers

Where a resource represents a piece of the system (and its desired state), a provider defines the steps that are needed to bring that piece of the system from its current state into the desired state.

The chef-client will determine the correct provider based on configuration data collected by Ohai at the start of the chef-client run. This configuration data is then mapped to a platform and an associated list of providers.

Generally, it’s best to let the chef-client choose the provider, and this is (by far) the most common approach. However, in some cases, specifying a provider may be desirable. There are two approaches:

  • Use a more specific short name—yum_package "foo" do instead of package "foo" do, script "foo" do instead of bash "foo" do, and so on—when available
  • Use the provider property within the resource block to specify the long name of the provider as a property of a resource. For example: provider Chef::Provider::Long::Name

This resource has the following providers:

Chef::Provider::Package, package
When this short name is used, the chef-client will attempt to determine the correct provider during the chef-client run.
Chef::Provider::Package::Rubygems, chef_gem
Can be used with the options attribute.

Examples

The following examples demonstrate various approaches for using resources in recipes. If you want to see examples of how Chef uses resources in recipes, take a closer look at the cookbooks that Chef authors and maintains: https://github.com/chef-cookbooks.

Compile time vs. converge time installation of gems

To install a gem while the chef-client is configuring the node (the “converge phase”), set the compile_time property to false:

chef_gem 'right_aws' do
  compile_time false
  action :install
end

To install a gem while the resource collection is being built (the “compile phase”), set the compile_time property to true:

chef_gem 'right_aws' do
  compile_time true
  action :install
end

Install MySQL for Chef

execute 'apt-get update' do
  ignore_failure true
  action :nothing
end.run_action(:run) if node['platform_family'] == 'debian'

node.set['build_essential']['compiletime'] = true
include_recipe 'build-essential'
include_recipe 'mysql::client'

node['mysql']['client']['packages'].each do |mysql_pack|
  resources("package[#{mysql_pack}]").run_action(:install)
end

chef_gem 'mysql'