Ignore Changes

In SLS blocks, use ignore_changes to prevent parameters from being updated on brown-field resources.

If a parameter is specified under ignore_changes then this parameter will be overridden with None and present() function will ignore updating such None-value parameters. Therefore only ‘Optional’ parameters can be included in ignore_changes, required parameters listed under ignore_changes are ignored.

In the following example, State_A is a green-field resource. During the first Idem run, Idem will create State_A resource with the tags value. However, since ignore_changes contains tags, during the second Idem run to update the State_A resource, Idem will not update tags even when the tags of the resource has been deviated away from the initial {tag-key: tag-value} value.

State_A:
   cloud.instance.present:
     - name: my-resource
     - tags: {tag-key: tag-value}
     - ignore_changes:
       - tags

Nested data under a parameter can be specified with a syntax similar to what arg_binding use: ‘:’ for traversing a dict structure and ‘[]’ for traversing a list. In addition, ‘[*]’ can be used to traverse through all elements in a list. For example: Given the tags input below, if we want to just ignore changing tag1, we can do tags[0]. Though, we need to be careful on ignoring list type data with indexing here, since the order of list elements is not guaranteed in Idem.

tags:
  - Name: tag1
    Value: value1
  - Name: tag2
    Value: value2

If the parameter path under ignore_changes is invalid, Idem will output a warning message but it won’t fail the resource management operation.

Note that the ignore_changes requisite only takes effect on a brown-field resource. That is, the enforced State_A exists in ESM cache or the resource_id has been supplied in the SLS file.