lifecycle

Resource instances have three phases: creation, update, and destruction. The lifecycle of a resource instance involves two or three of the phases. The meta-argument lifecycle can be used to modify the lifecycle of a resource instance and includes the following arguments:

• create_before_destroy

  By default, when you need to change a resource argument that cannot be updated, Terraform destroys the existing instance and then uses the newly configured arguments to create a new object for replacement. When you set the create_before_destroy argument to true, Terraform creates a new instance before destroying the existing instance. This argument applies to scenarios where service continuity needs to be ensured. Ensure in advance that each resource instance has a unique name and other constraints are met so that old and new instances can co-exist.

  lifecycle {
    create_before_destroy = true
  }

• prevent_destroy

  When prevent_destroy is set to true, Terraform blocks the deletion of the resource and returns an error. This meta-argument can be used as a security measure to prevent high-cost instances, such as database instances, from being recreated due to unexpected operations. To delete the resource, you need to delete the configuration and then perform the destroy operation.

  lifecycle {
    prevent_destroy = true
  }

• ignore_changes

  By default, the Terraform plan/apply operation detects the differences between the cloud resource attributes and the local resource blocks. If they are inconsistent, the update or rebuild operation is invoked to match the configuration. You can use ignore_changes specify arguments that Terraform should ignore when planning updates or rebuilds. The value of ignore_changes can be the relative address list of the attributes. The Map and List elements can be referenced using index notation, such as tags["Name"] and list[0].

    ...
    lifecycle {
      ignore_changes = [
        name,
      ]
    }
  }

  In this case, Terraform ignores the modification of the name argument. In addition to the list, you can also use the keyword all to ignore the updates of all attributes.

    ...
    lifecycle {
      ignore_changes = all
    }
  }