notify_group Resource

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To suggest a change, edit the notify_group.rb file and submit a pull request to the Chef Infra Client repository.

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The notify_group resource does nothing, and always fires notifications which are set on it. Use it to DRY blocks of notifications that are common to multiple resources, and provide a single target for other resources to notify. Unlike most resources, its default action is :nothing.

New in Chef Infra Client 15.8.

Syntax

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

notify_group 'name' do
  action      Symbol # defaults to :nothing if not specified
end

where:

notify_group is the resource.
name is the name given to the resource block.
action identifies which steps Chef Infra Client will take to bring the node into the desired state.

Actions

The notify_group resource has the following actions:

:nothing: This resource block doesn’t act unless notified by another resource to take action. Once notified, this resource block either runs immediately or is queued up to run at the end of a Chef Infra Client run. (default)
:run

Properties

This resource does not have any properties.

Common Resource Functionality

Chef resources include common properties, notifications, and resource guards.

Common Properties

The following properties are common to every resource:

compile_time

Ruby Type: true, false | Default Value: false

Control the phase during which the resource is run on the node. Set to true to run while the resource collection is being built (the compile phase). Set to false to run while Chef Infra Client is configuring the node (the converge phase).

ignore_failure

Ruby Type: true, false, :quiet | Default Value: false

Continue running a recipe if a resource fails for any reason. :quiet won’t display the full stack trace and the recipe will continue to run if a resource fails.

retries

Ruby Type: Integer | Default Value: 0

The number of attempts to catch exceptions and retry the resource.

retry_delay

Ruby Type: Integer | Default Value: 2

The delay in seconds between retry attempts.

sensitive

Ruby Type: true, false | Default Value: false

Ensure that sensitive resource data isn’t logged by Chef Infra Client.

Notifications

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 notify more than one resource; use a notifies statement for each resource to be notified.

If the referenced resource doesn’t exist, an error is raised. In contrast, subscribes won’t fail if the source resource isn’t found.

A timer specifies the point during a Chef Infra 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 end of a Chef Infra Client run.
:immediate, :immediately: Specifies that a notification should be run immediately, for each resource notified.

The syntax for notifies is:

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

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.

Note that subscribes doesn’t apply the specified action to the resource that it listens to - for example:

file '/etc/nginx/ssl/example.crt' do
  mode '0600'
  owner 'root'
end

service 'nginx' do
  subscribes :reload, 'file[/etc/nginx/ssl/example.crt]', :immediately
end

In this case the subscribes property reloads the nginx service whenever its certificate file, located under /etc/nginx/ssl/example.crt, is updated. subscribes doesn’t make any changes to the certificate file itself, it merely listens for a change to the file, and executes the :reload action for its resource (in this example nginx) when a change is detected.

If the other resource doesn’t exist, the subscription won’t raise an error. Contrast this with the stricter semantics of notifies, which will raise an error if the other resource doesn’t exist.

A timer specifies the point during a Chef Infra 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 end of a Chef Infra Client run.
:immediate, :immediately: Specifies that a notification should be run immediately, for each resource notified.

The syntax for subscribes is:

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

Guards

A guard property can be used to evaluate the state of a node during the execution phase of a Chef Infra Client run. Based on the results of this evaluation, a guard property is then used to tell Chef Infra Client if it should continue executing a resource. A guard property accepts either a string value or a Ruby block value:

A string is executed as a shell command. If the command returns 0, the guard is applied. If the command returns any other value, then the guard property isn’t applied. String guards in a powershell_script run Windows PowerShell commands and may return true in addition to 0.
A block is executed as Ruby code that must return either true or false. If the block returns true, the guard property is applied. If the block returns false, the guard property isn’t applied.

A guard property is useful for ensuring that a resource is idempotent by allowing that resource to test for the desired state as it’s being executed, and then if the desired state is present, for Chef Infra Client to don’thing.

Properties

The following properties can be used to define a guard that’s evaluated during the execution phase of a Chef Infra Client run:

not_if: Prevent a resource from executing when the condition returns true.
only_if: Allow a resource to execute only if the condition returns true.

Examples

The following examples demonstrate various approaches for using the notify_group resource in recipes:

Wire up a notification from a service resource to stop and start the service with a 60 second delay.

service "crude" do
  action [ :enable, :start ]
end

chef_sleep "60" do
  action :nothing
end

# Example code for a hypothetical badly behaved service that requires
# 60 seconds between a stop and start in order to restart the service
# (due to race conditions, bleeding connections down, resources that only
# slowly unlock in the background, or other poor software behaviors that
# are sometimes encountered).
#
notify_group "crude_stop_and_start" do
  notifies :stop, "service[crude]", :immediately
  notifies :sleep, "chef_sleep[60]", :immediately
  notifies :start, "service[crude]", :immediately
end

template "/etc/crude/crude.conf" do
  source "crude.conf.erb"
  variables node["crude"]
  notifies :run, "notify_group[crude_stop_and_start]", :immediately
end