Task 4.1: Use and differentiate resource and data blocks

• AA resource block for the image, so Terraform creates a fresh image every month

  Incorrect

  A resource would make Terraform create and own an image, which the image team already publishes.

• BA variable that the image team updates in the configuration's default value every month

  Incorrect

  That still hard-codes the ID, only in a different place, and needs a person each month.

• CA data block that looks up the newest image matching the name pattern

  Correct

  Data sources read information about existing infrastructure for use in the configuration without managing it.

• DAn output that exports the image ID from the image team's console session

  Incorrect

  Outputs expose values from a configuration; they cannot read another system's console.

Resources are what Terraform manages; data sources are what it only reads.

• Aaws_vpc.shared.id

  Incorrect

  Without the data. prefix, this refers to a managed resource.

• Bdata.shared.aws_vpc.id

  Incorrect

  The type comes before the name.

• Cdata.aws_vpc.shared.id

  Correct

  Data sources are referenced as data.<TYPE>.<NAME>.<ATTRIBUTE>.

• Dvar.aws_vpc.shared.id

  Incorrect

  var. refers to input variables.

Managed resources: <TYPE>.<NAME>. Data sources: data.<TYPE>.<NAME>.

• AFive separate data blocks, because data blocks accept neither count nor for_each

  Incorrect

  Data blocks accept the same repetition meta-arguments as resource blocks, so one block can read many objects.

• BOne data block with for_each = var.subnet_ids, reading each.value as the ID

  Correct

  A data block supports for_each, creating one data instance per element, each of which Terraform reads.

• CA resource block with for_each over the IDs, which adopts the subnets without changing them

  Incorrect

  A resource block declares objects for Terraform to create and manage; it does not read existing subnets by ID.

• DOne data block wrapped in a dynamic block that repeats it once per ID

  Incorrect

  dynamic generates nested blocks inside a block; it cannot repeat a whole data block.

Data blocks take count and for_each just as resource blocks do, so one block can read a whole collection of existing objects.

• AOnly create it; later changes need a new resource block

  Incorrect

  Terraform updates and replaces existing resources too.

• BCreate, update in place, or destroy and re-create it

  Correct

  Applying a configuration creates, updates in place, destroys, or destroys and re-creates resources to match.

• COnly read it, the same way as a data source

  Incorrect

  Reading only is what data sources do.

• DCreate it, then hand it to the provider, which manages it from then on

  Incorrect

  Terraform keeps managing the resource through its state.

A managed resource has a full lifecycle under Terraform.

• ADuring planning

  Correct

  Terraform attempts to query data sources during the planning phase, and literal arguments give it everything it needs to do so.

• BOnly after apply, once all resources exist

  Incorrect

  Reading moves to apply only in special cases, and literal arguments are not one of them.

• COnly during terraform init

  Incorrect

  init prepares the working directory and reads no data sources.

• DOnce, after which the result is fixed forever

  Incorrect

  Data sources are read again on each run.

Data sources are normally read at plan time, so plans can show real values.

• AIt keeps the first result in the dependency lock file and never recalculates it

  Incorrect

  The lock file is for provider versions.

• BIt creates a managed resource from the result on the first apply

  Incorrect

  Data sources never become managed resources.

• CIt requires an import before the result can be used

  Incorrect

  Import is for existing managed objects.

• DIt re-calculates the data on each plan

  Correct

  Specialized utility data sources generate data that exists only during the operation; Terraform re-calculates it on consecutive plans.

Not every data source talks to an API; some just compute values every run.