http_request Resource

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Use the http_request resource to send an HTTP request (GET, PUT, POST, DELETE, HEAD, or OPTIONS) with an arbitrary message. This resource is often useful when custom callbacks are necessary.

Syntax

A http_request resource block sends HTTP requests with an arbitrary message. For example, send a DELETE request to 'http://www.chef.io/some_page?message=please_delete_me'.

http_request 'please_delete_me' do
  url 'http://www.chef.io/some_page'
  action :delete
end

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

http_request 'name' do
  headers                    Hash
  message                    Object # defaults to 'name' if not specified
  url                        String
  action                     Symbol # defaults to :get if not specified
end

where:

• http_request 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.
• headers, message, and url 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

The http_request resource has the following actions:

:delete

Send a DELETE request.

:get

Default. Send a GET request. Changed in Chef Client 12.0 to deprecate the hard-coded query string from earlier versions. Cookbooks that rely on this string need to be updated to manually add it to the URL as it is passed to the resource.

:head

Send a HEAD request.

:nothing

This resource block does not 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.

:options

Send an OPTIONS request.

:post

Send a POST request.

:put

Send a PUT request.

Properties

The http_request resource has the following properties:

headers

Ruby Type: Hash

A Hash of custom headers.

message

Ruby Type: Object

The message that is sent by the HTTP request. Default value: the name of the resource block. See “Syntax” section above for more information.

url

Ruby Type: String

The URL to which an HTTP request is sent.

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 will not 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 retry delay (in seconds).

sensitive

Ruby Type: true, false | Default Value: false

Ensure that sensitive resource data is not logged by Chef InfraClient.

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 does not exist, an error is raised. In contrast, subscribes will not fail if the source resource is not 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, per 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 does not 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 does not 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 does not exist, the subscription will not raise an error. Contrast this with the stricter semantics of notifies, which will raise an error if the other resource does not 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, per 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 is not 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 is not 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 is being executed, and then if the desired state is present, for Chef Infra Client to do nothing.

The following properties can be used to define a guard that is 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 http_request resource in recipes:

Send a GET request

http_request 'some_message' do
  url 'http://example.com/check_in'
end

The message is sent as http://example.com/check_in?message=some_message.

Send a POST request

To send a POST request as JSON data, convert the message to JSON and include the correct content-type header. For example:

http_request 'posting data' do
  action :post
  url 'http://example.com/check_in'
  message ({:some => 'data'}.to_json)
  headers({'AUTHORIZATION' => "Basic #{
    Base64.encode64('username:password')}",
    'Content-Type' => 'application/data'
  })
end

Transfer a file only when the remote source changes

remote_file '/tmp/couch.png' do
  source 'http://couchdb.apache.org/img/sketch.png'
  action :nothing
end

http_request 'HEAD http://couchdb.apache.org/img/sketch.png' do
  message ''
  url 'http://couchdb.apache.org/img/sketch.png'
  action :head
  if ::File.exist?('/tmp/couch.png')
    headers 'If-Modified-Since' => File.mtime('/tmp/couch.png').httpdate
  end
  notifies :create, 'remote_file[/tmp/couch.png]', :immediately
end