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Revisit ephemeral resources decision about plan files (#2996)

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Signed-off-by: Andrei Ciobanu <andrei.ciobanu@opentofu.org>
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Andrei Ciobanu
2025-07-08 10:10:22 +03:00
committed by GitHub
parent eaee31f920
commit 11780773aa
1 changed files with 20 additions and 3 deletions
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rfc/20250317-ephemeral-resources.md
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@@ -125,7 +125,7 @@ If OpenTofu finds an ephemeral value given to a non-ephemeral variable in a modu
OpenTofu should not store ephemeral variable(s) in plan files.
If a plan is generated from a configuration that is having at least one ephemeral variable,
when the planfile will be applied, the value(s) for the ephemeral variable(s) needs to be provided again.
when the plan file will be applied, the value(s) for the ephemeral variable(s) needs to be provided again.
#### Outputs
Most `output` blocks can be configured as ephemeral.
@@ -220,7 +220,8 @@ Locals marked as ephemeral are available during plan and apply phase and can be
* `connection` and `provisioner` blocks
#### Ephemeral resource
In contrast with the write-only arguments where only specifically tagged attributes are not stored in the state/plan file, `ephemeral` resources are not stored entirely.
In contrast with the write-only arguments where only specifically tagged attributes are not stored in the state/plan file, `ephemeral` resources must not be stored in the state file and have only a reference stored in the plan file.
The ephemeral blocks are behaving similar to `data`, where it reads the indicated resource and once it's done with it, is going to close it.
Ephemeral resources can be referenced only in specific contexts:
@@ -262,6 +263,7 @@ The only `lifecycle` content that ephemerals should support are `precondition` a
```
The meta-arguments `provisioner` and `connection` should not be supported.
#### Providers
`provider` block is ephemeral by nature, meaning that the configuration of this is never stored into state/plan file.
@@ -698,7 +700,7 @@ locals {
Once a local is marked as ephemeral, this can be used only in other ephemeral contexts. Check the `Proposed Solution` section for more details on the allowed contexts.
### Ephemeral resources
Due to the fact ephemeral resources are not stored in the state/plan file, this block is not creating a diff in the OpenTofu's UI.
Due to the fact ephemeral resources are not stored in the state, this block is not creating a diff in the OpenTofu's UI.
Instead, OpenTofu should notify the user of opening/renewing/closing an ephemeral resource with messages similar to the following:
```bash
ephemeral.playground_random.password: Opening...
@@ -807,6 +809,21 @@ in the state file we should see the following:
}
```
#### Plan file
During the implementation of the ephemeral resources execution, we had to make a decision on how we can include ephemeral resources
in the execution graph for the `apply` phase, especially when `tofu` is executed with a plan file.
There were two immediate options available:
* Add a new graph transformer (or enhance the expansion one from the apply graph steps) to create a subgraph responsible with the creation of concrete nodes for the ephemeral resources in the configuration.
* Use the already planned ephemeral resources and store only a stub in the changes to enable the already existing `DiffTransformer` to create concrete graph nodes based on the changelist.
We went with the second to ensure that the flow is consistent between `tofu apply -auto-aprove` and `tofu plan -out planfile && tofu apply planfile`.
The information from the ephemeral resources that is stored in the plan file is limited to only the address of the resource and the action (ie: OPEN).
Anything else related to this type of changes, are trimmed out and must never be stored in the plan file.
> [!NOTE]
>
> For more details please refer to [#2985](https://github.com/opentofu/opentofu/pull/2985).
### Testing support
Due to the scope size this RFC is covering, the testing support will be documented later into a different RFC, or as amendment to this one.