reconstructed

reconstructed is an Ansible inventory plugin which can be used to generate group hierarchies and place hosts within them based solely on host facts. This allows functionality similar to what the ansible.builtin.add_host module can provide, but it is available during inventory construction rather than playbook execution.

Installation from Ansible Galaxy

You can install the latest version from Ansible Galaxy repository.

ansible-galaxy collection install -U tseeker.reconstructed

If you are using a requirements.yml file to download collections and roles, you can use these lines:

collections:
  - tseeker.reconstructed

Usage

A reconstructed script can be added to the inventory by creating a YAML file in the inventory, with the following structure:

---
plugin: tseeker.reconstructed.reconstructed
instructions:
  - action: ...
  - action: ...
    # ...

Script actions are somewhat similar to playbook tasks. Once a script has been added, it will be executed once for each host in the input inventory.

Each action record in a script must include an action field, which describes the action to perform. In addition, it may include fields which contain the action's details, as well as fields which implement various controls that apply to an action (loops, local variables, etc).

The script can manipulate and use host facts. In addition, local variables which do not pollute the inventory are used automatically for e.g. loops, and can be defined manually.

Actions

The following actions may be used in a reconstructed script.

add_child

This action adds an existing group to the set of another existing group's children.

It supports the following fields.

• group must contain the name of the parent group, or a Jinja template that evaluates to that name. The group must exist.
• child must contain the name of the child group, or a Jinja template that evaluates to that name. The group must exist.

add_host

The add_host action can be used to add the inventory host currently being processed to a group.

The following field is supported.

• group must contain the name of the group to add the host to. It may be a Jinja template. The group in question must exist.

block

The block action can be used to group multiple actions and to support error recovery, behaving in many ways like the playbooks' block. The following fields may be used.

• block contains the block's main list of instructions.
• rescue contains a list of instructions that will be executed if an error occurs while executing the main list. The reconstructed_error local variable will contain the message of the error that caused the rescue list to be executed. This field may be omitted.
• always contains a list of instructions that will be executed after both other lists, independently of any error. This field may be omitted.

create_group

The create_group action creates an inventory group. In addition, it may specify the new group's parent and add the current host to the group.

If the group already exists, no error will be raised. The group will be added to the specified parent and the host will be added to the group if requested.

The following fields are supported.

• group contains the name of the group. It must be present and may contain a Jinja template.
• parent may contain the name of an additional group to which the new group will be added as a child. The group in question must exist. This field is optional and may contain a Jinja template.
• If the add_host field is present, it may contain a boolean which will determine whether the current inventory host must be added to the group.

fail

This action causes the script to fail immediately. The following field may be used:

• msg may contain a message (or a Jinja template resulting in a message) to write to the output. By default the message will be fail requested followed by the name of the current host.

rename_host

This action changes the name of the current host. It can only be executed once for each host. The actual renaming will occur after the script has completed its execution. It requires the following field:

• name: the new name of the host.

set_fact

This action sets an Ansible fact associated to the current host. The following fields must be set:

• name is the name of the fact to set, or a Jinja template returning the name. It must represent a valid fact name.
• value is the fact's new value, or a template computing it.

set_var

This action sets a local variable. Local variables are only kept for the duration of the script's execution for a given host. A local variable will hide a fact by the same name.

The following fields are required:

• name is the name of the fact to set, or a Jinja template returning the name. It must result in a valid fact name.
• value is the variable's new value, or a template computing it.

stop

The stop action interrupts the execution of the script for the current host. It requires no additional information.

Control fields

The following additional fields may be added to any action record to alter its behaviour.

run_once

If this field is set to a true, it will cause the action to be executed only once.

loop and loop_var

The loop field may contain a list or a Jinja template that evaluates to a list. The action record will be repeated for each item in the list, with a local variable set to the value of the item.

By default the variable that contains the item is called item. However it is possible to add a loop_var field containing a valid variable name to change it. This variable will be restored to its previous state once the loop is finished.

vars

The vars field may contain a table of local variables to set for the duration of the action. The table's keys are variable names, and its values will be evaluated using Jinja. During a loop, variables will be evaluated evaluated once for each loop iteration. Once the action is finished, the local variables defined using vars will disappear.

when

The when field may be used to check a condition and prevent the execution of the action it is bound to if the condition isn't satisfied. The condition is evaluated once for each iteration of a loop. All local variables defined using vars are available for use in the condition.

To do

• create_group.add_host should allow Jinja templates
• Add a debug action