Custom resource guide

To use custom resources in Agentless Mode, update the provider properties and Ruby IO class methods of your custom resources so that Chef Infra Client can run them on a remote node.

Providers

Providers determine whether Chef Infra Client can locally or remotely run a resource on a node.

To enable Infra Client to run a resource locally or remotely, use the agent_mode and target_mode properties to define the environments that the resource can run in.

agent_mode

Whether Chef Infra Client can execute the resource locally on a node.

Default value: true

target_mode

Whether Chef Infra Client can execute the resource on a node from a remote connection.

Default value: false

Examples

You can combine these properties to define whether Chef Infra Client can run a custom resource locally on a node, on a node from a remote connection, or both.

Only execute a resource locally

Chef Infra Client only executes this resource locally on a node as target_mode is set to false and agent_mode defaults to true:

provides :<RESOURCE_NAME>, target_mode: false

Only execute a resource remotely

Chef Infra Client executes this resource from a remote connection, but not locally:

provides :<RESOURCE_NAME>, target_mode: true, agent_mode: false

Execute a resource remotely and locally

Chef Infra Client executes this resource from a remote connection and also locally:

provides :<RESOURCE_NAME>, target_mode: true, agent_mode: true`

Input/output operations in Agentless Mode

Agentless Mode includes an input/output (IO) abstraction layer.

IO operations in Chef Infra resources fall into two different groups:

• Shell commands using shell_out or shell_out!.
• Native IO using TargetIO classes.

shell_out

Any implementations using shell_out is automatically Agentless Mode-capable, as the execution target dynamically changes between local and remote invocations.

For more information on using shell_out, see the shell_out documentation.

TargetIO

Update custom resources that use Ruby’s built-in IO classes and methods to run in Agentless Mode by prefixing each IO call with the TargetIO namespace.

For example, to update Ruby’s IO.read class to run in Agentless Mode, modify this:

contents = IO.read(filename)

to:

contents = TargetIO::IO.read(filename)

In Agentless Mode, TargetIO translates native Ruby IO calls so they can be executed on a remote node. When run locally in Agent Mode, it automatically passes operations to Ruby’s native IO classes.

The following classes run the most commonly used IO calls:

• TargetIO::Dir
• TargetIO::Etc
• TargetIO::File
• TargetIO::FileUtils
• TargetIO::HTTP
• TargetIO::IO
• TargetIO::Shadow