log Resource

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Use the log resource to create log entries. The log resource behaves like any other resource: built into the resource collection during the compile phase, and then run during the execution phase. (To create a log entry that is not built into the resource collection, use Chef::Log instead of the log resource.)

Syntax

A log resource block adds messages to the log file based on events that occur during a Chef Infra Client run:

log 'message' do
  message 'A message add to the log.'
  level :info
end

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

log 'name' do
  level        Symbol # default value: :info
  message      String # default value: 'name' unless specified
  action       Symbol # defaults to :write if not specified
end

where:

• log 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.
• level and message are the properties available to this resource.

Actions

The log 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.

:write

(default)

Properties

The log resource has the following properties:

level

Ruby Type: Symbol | Default Value: :info

The logging level for displaying this message. Options (in order of priority): :debug, :info, :warn, :error, and :fatal.

message

Ruby Type: String | Default Value: The resource block's name

The message to be added to a log file. Default value: the name of the resource block. See “Syntax” section above for more information.

Log Entries

Chef::Log will print log entries to the default logger that’s configured for the machine on which Chef Infra Client is running. (To create a log entry that’s built into the resource collection, use the log resource instead of Chef::Log.)

Supported log levels

The following example shows a series of fatal Chef::Log entries:

unless node['splunk']['upgrade_enabled']
  Chef::Log.fatal('The chef-splunk::upgrade recipe was added to the node,')
  Chef::Log.fatal('but the attribute `node["splunk"]["upgrade_enabled"]` wasn\'t set.')
  Chef::Log.fatal('I am bailing here so this node doesn\'t upgrade.')
  raise
end

service 'splunk_stop' do
  service_name 'splunk'
  supports status: true
  action :stop
end

if node['splunk']['is_server']
  splunk_package = 'splunk'
  url_type = 'server'
else
  splunk_package = 'splunkforwarder'
  url_type = 'forwarder'
end

splunk_installer splunk_package do
  url node['splunk']['upgrade']["#{url_type}_url"]
end

if node['splunk']['accept_license']
  execute 'splunk-unattended-upgrade' do
    command "#{splunk_cmd} start --accept-license --answer-yes"
  end
else
  Chef::Log.fatal('You didn\'t accept the license (set node["splunk"]["accept_license"] to true)')
  Chef::Log.fatal('Splunk is stopped and can\'t be restarted until the license is accepted!')
  raise
end

The following example shows using multiple Chef::Log entry types:

...

begin
  aws = Chef::DataBagItem.load(:aws, :main)
  Chef::Log.info("Loaded AWS information from DataBagItem aws[#{aws['id']}]")
rescue
  Chef::Log.fatal("Couldn't find the 'main' item in the 'aws' data bag")
  raise
end

...

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.

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 log resource in recipes:

Set default logging level

log 'a string to log'

Set debug logging level

log 'a debug string' do
  level :debug
end

Add a message to a log file

log 'message' do
  message 'This is the message that will be added to the log.'
  level :info
end