The three pieces on choudoufu

Identity

Mon, 01 Jan 0001 00:00:00 +0000

Identity#

Which real resource a configuration address refers to. AWS already knows this, once you tell it.

Two tags, written as the resource is created.

tofu-estate = prod-networking
tofu-address = aws_vpc.main

That pair is the entire ownership contract. Any tool that can write two tags can adopt a resource. Any tool that can read them can tell you what an estate contains.

Values

Mon, 01 Jan 0001 00:00:00 +0000

Values#

Most resources need nothing here. A resource with a cloud twin recovers its values by reading the live object, the same way it recovers its identity.

The exceptions are resources with no twin at all. Nothing in AWS knows a null_resource ran a script, a time_static captured a timestamp, or a random_pet generated a name.

Those persist as one small record each. Declare a store and they are admitted. Without one they are refused.

Effects

Mon, 01 Jan 0001 00:00:00 +0000

Effects#

A migration that ran. A cache that was invalidated. A notification that was sent. None of them leaves anything in the cloud to read back, so no plan can tell you whether it already happened.

A receipt is how you make it visible.

What a receipt is#

An ordinary resource you declare, by convention an SSM parameter at /tofu-receipts/<estate>/<effect> holding a hash of the effect’s input.

Two runs at once

Mon, 01 Jan 0001 00:00:00 +0000

Two runs at once#

Ownership lives on the resources themselves, and records settle concurrent writes by conditional write. Two simultaneous applies against one estate resolve one of four ways.

Race	Outcome
Two creates of the same client-named resource	The cloud’s uniqueness constraint rejects the second. The loser re-plans, binds to the winner’s resource, and comes back clean.
Two creates of the same server-assigned resource	Both are created. The next plan reports a marker collision naming both live IDs and refuses rather than guessing. A human deletes one.
Divergent in-place updates	Last writer wins at the API. The next plan reads the live system and converges.
An update racing a destroy	The loser gets not-found, re-plans, and converges.

No race orphans a resource silently. Each case is a clean re-plan or a named collision.