github.com/hugorut/terraform@v1.1.3/website/docs/language/meta-arguments/lifecycle.mdx (about)

     1  ---
     2  page_title: The lifecycle Meta-Argument - Configuration Language
     3  description: >-
     4    The meta-arguments in a lifecycle block allow you to customize resource
     5    behavior.
     6  ---
     7  
     8  # The `lifecycle` Meta-Argument
     9  
    10  > **Hands-on:** Try the [Lifecycle Management](https://learn.hashicorp.com/tutorials/terraform/resource-lifecycle?utm_source=WEBSITE&utm_medium=WEB_IO&utm_offer=ARTICLE_PAGE&utm_content=DOCS) tutorial on HashiCorp Learn.
    11  
    12  The general lifecycle for resources is described in the
    13  [Resource Behavior](/language/resources/behavior) page. Some details of
    14  that behavior can be customized using the special nested `lifecycle` block
    15  within a resource block body:
    16  
    17  ```hcl
    18  resource "azurerm_resource_group" "example" {
    19    # ...
    20  
    21    lifecycle {
    22      create_before_destroy = true
    23    }
    24  }
    25  ```
    26  
    27  ## Syntax and Arguments
    28  
    29  `lifecycle` is a nested block that can appear within a resource block.
    30  The `lifecycle` block and its contents are meta-arguments, available
    31  for all `resource` blocks regardless of type.
    32  
    33  The following arguments can be used within a `lifecycle` block:
    34  
    35  * `create_before_destroy` (bool) - By default, when Terraform must change
    36    a resource argument that cannot be updated in-place due to
    37    remote API limitations, Terraform will instead destroy the existing object
    38    and then create a new replacement object with the new configured arguments.
    39  
    40    The `create_before_destroy` meta-argument changes this behavior so that
    41    the new replacement object is created _first,_ and the prior object
    42    is destroyed after the replacement is created.
    43  
    44    This is an opt-in behavior because many remote object types have unique
    45    name requirements or other constraints that must be accommodated for
    46    both a new and an old object to exist concurrently. Some resource types
    47    offer special options to append a random suffix onto each object name to
    48    avoid collisions, for example. Terraform CLI cannot automatically activate
    49    such features, so you must understand the constraints for each resource
    50    type before using `create_before_destroy` with it.
    51  
    52    Destroy provisioners of this resource will not run if `create_before_destroy`
    53    is set to `true`. We may address this in the future, and this [GitHub issue](https://github.com/hugorut/terraform/issues/13549) contains more details.
    54  
    55  * `prevent_destroy` (bool) - This meta-argument, when set to `true`, will
    56    cause Terraform to reject with an error any plan that would destroy the
    57    infrastructure object associated with the resource, as long as the argument
    58    remains present in the configuration.
    59  
    60    This can be used as a measure of safety against the accidental replacement
    61    of objects that may be costly to reproduce, such as database instances.
    62    However, it will make certain configuration changes impossible to apply,
    63    and will prevent the use of the `terraform destroy` command once such
    64    objects are created, and so this option should be used sparingly.
    65  
    66    Since this argument must be present in configuration for the protection to
    67    apply, note that this setting does not prevent the remote object from
    68    being destroyed if the `resource` block were removed from configuration
    69    entirely: in that case, the `prevent_destroy` setting is removed along
    70    with it, and so Terraform will allow the destroy operation to succeed.
    71  
    72  * `ignore_changes` (list of attribute names) - By default, Terraform detects
    73    any difference in the current settings of a real infrastructure object
    74    and plans to update the remote object to match configuration.
    75  
    76    The `ignore_changes` feature is intended to be used when a resource is
    77    created with references to data that may change in the future, but should
    78    not affect said resource after its creation. In some rare cases, settings
    79    of a remote object are modified by processes outside of Terraform, which
    80    Terraform would then attempt to "fix" on the next run. In order to make
    81    Terraform share management responsibilities of a single object with a
    82    separate process, the `ignore_changes` meta-argument specifies resource
    83    attributes that Terraform should ignore when planning updates to the
    84    associated remote object.
    85  
    86    The arguments corresponding to the given attribute names are considered
    87    when planning a _create_ operation, but are ignored when planning an
    88    _update_. The arguments are the relative address of the attributes in the
    89    resource. Map and list elements can be referenced using index notation,
    90    like `tags["Name"]` and `list[0]` respectively.
    91  
    92    ```hcl
    93    resource "aws_instance" "example" {
    94      # ...
    95  
    96      lifecycle {
    97        ignore_changes = [
    98          # Ignore changes to tags, e.g. because a management agent
    99          # updates these based on some ruleset managed elsewhere.
   100          tags,
   101        ]
   102      }
   103    }
   104    ```
   105  
   106    Instead of a list, the special keyword `all` may be used to instruct
   107    Terraform to ignore _all_ attributes, which means that Terraform can
   108    create and destroy the remote object but will never propose updates to it.
   109  
   110    Only attributes defined by the resource type can be ignored.
   111    `ignore_changes` cannot be applied to itself or to any other meta-arguments.
   112  
   113  ## Literal Values Only
   114  
   115  The `lifecycle` settings all affect how Terraform constructs and traverses
   116  the dependency graph. As a result, only literal values can be used because
   117  the processing happens too early for arbitrary expression evaluation.