KEP 98: Promotion Phase for GitOps use cases (#107)

* add KEP

Signed-off-by: Moritz Wiesinger <[email protected]>

* Update text/0098-promotion-phase.md

Co-authored-by: Giovanni Liva <[email protected]>
Signed-off-by: Moritz Wiesinger <[email protected]>

* add open question about failure state

Signed-off-by: Moritz Wiesinger <[email protected]>

* review

Signed-off-by: Moritz Wiesinger <[email protected]>

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Signed-off-by: Moritz Wiesinger <[email protected]>
Co-authored-by: Giovanni Liva <[email protected]>

Author: mowies

text/0098-promotion-phase.md

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+# Promotion Phase for GitOps use cases
+
+Add a new lifecycle phase after post deployment dedicated to GitOps promotion tasks.
+
+**State: DRAFTING**
+
+## Motivation
+
+By introducing a dedicated stage after the post Application deployment phase for promotion tasks, we will
+enable users to automatically promote their apps into another stage/cluster/environment.
+This will make it much clearer for Keptn users how to set up their GitOps-assisted workflows in multi-stage
+environments.
+
+## Explanation
+
+The new promotion phase can be used by adding a list of references to `KeptnTaskDefinition` resources to a new field
+called `promotionTasks` inside the `KeptnAppContext` CRD. Keptn will use this list the same way as for other phases
+like post-deployment and execute the referenced tasks in parallel using Kubernetes Job resources.
+
+## Trade-offs and mitigations
+
+No real drawbacks come to mind, except some slight slowdown in progression of the lifecycle since the new phase
+needs to be executed and the lifecycle-operator needs to check if any tasks need to be run.
+
+## Breaking changes
+
+This KEP would not have any breaking changes. The `KeptnAppContext` CRD would get an additional field called
+`PromotionTasks` which contains a list of references to `KeptnTaskDefintion` resources that should be executed in this
+phase.
+
+## Prior art and alternatives
+
+The alternative to this KEP is that users re-purpose the post-deployment phase for promotion, which would limit
+flexibility since users lose the option to not promote when post-deployment tasks fail.
+
+## Open questions
+
+One open point is how the new phase influences the failure or passing state of the overall deployment of a user's
+application.
+What happens when everything passes, but a promotion task fails?
+My suggestion would be to let users configure this through some settings. Similar to the non-blocking behaviour
+suggested in [#1934](https://github.com/keptn/lifecycle-toolkit/issues/1934), users could then decide
+if a failing promotion task should fail the overall deployment.
+
+## Future possibilities
+
+For now, none.