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Flow control SubReconcilers #414

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merged 2 commits into from
Aug 31, 2023
Merged

Flow control SubReconcilers #414

merged 2 commits into from
Aug 31, 2023

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scothis
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@scothis scothis commented Aug 23, 2023

Spike of reconcilers that direct the flow of a reconcile request at runtime.

  • IfThen - branch execution based on a boolean condition
  • While - iterate over a reconciler while a condition is true
  • TryCatch - recover from errors or rewrite the result
  • OverrideSetup - suppress calls to the SetupWithManager method

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codecov bot commented Aug 23, 2023

Codecov Report

Patch coverage: 60.00% and project coverage change: -0.04% ⚠️

Comparison is base (5be8c31) 60.62% compared to head (b21b653) 60.58%.

❗ Current head b21b653 differs from pull request most recent head 0c211d9. Consider uploading reports for the commit 0c211d9 to get more accurate results

Additional details and impacted files
@@            Coverage Diff             @@
##             main     #414      +/-   ##
==========================================
- Coverage   60.62%   60.58%   -0.04%     
==========================================
  Files          24       25       +1     
  Lines        2334     2489     +155     
==========================================
+ Hits         1415     1508      +93     
- Misses        835      895      +60     
- Partials       84       86       +2     
Files Changed Coverage Δ
reconcilers/flow.go 60.00% <60.00%> (ø)

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Comment on lines +235 to +312
// Catch is called with the results from Try(). New results can be returned
// suppressing the original results.
//
// +optional
Catch func(ctx context.Context, resource Type, result Result, err error) (Result, error)
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@mamachanko mamachanko Aug 24, 2023

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After trying TryCatch on for size mentally, I am wondering if an advice-style reconciler could be implemented with it. For example, could one update a single condition on a resource depending on whether a collection of steps was successful or not like so?

func ApplyResources(c reconcilers.Config) *reconcilers.SubReconciler {
	return &TryCatch{
		Try: reconcilers.Sequence{
			ApplyRegistryCredentialsPlaceholder(c),
			ApplyCerts(c),
			ApplyRedis(c, images.Redis),
			ApplyAuthServer(c, images.AuthServer),
			ApplyTokenSignatureKeys(c),
		},
		Catch: func(ctx, parent *v1alpha1.AuthServer, result Result, err error) {
			if err != nil {
				parent.Status.MarkResourcesError(ctx, err.Error())
				return result, nil
			} else {
				parent.Status.MarkResourcesApplied(ctx)
				return result, nil
			}
		},
		Config: c,
	}
}

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Exactly. You'd probably want to do a little bit of detection on the err to figure out if it is something that should be suppressed or continued.

Reconcilers that direct the flow of a reconcile request at runtime.

- IfThen - branch execution based on a boolean condition
- While - iterate over a reconciler while a condition is true
- TryCatch - recover from errors or rewrite the result
- OverrideSetup - suppress calls to the SetupWithManager method

Signed-off-by: Scott Andrews <[email protected]>
@scothis scothis marked this pull request as ready for review August 29, 2023 22:05
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left a few questions and suggestions

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#### While

A [`While`](https://pkg.go.dev/github.com/vmware-labs/reconciler-runtime/reconcilers#While) calls the reconciler so long as the condition is true, up to the maximum number of iterations (defaults to 100). The current iteration index can be retried with [`RetrieveIteration`](https://pkg.go.dev/github.com/vmware-labs/reconciler-runtime/reconcilers#RetrieveIteration).
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[question, clarification] Iteration is done as a single resource's reconciliation, isn't it? And it's only iterating over the While and not the entire pipeline of reconcilers?

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}
},
Catch: func(ctx context.Context, resource *buildv1alpha1.Function, result reconcile.Result, err error) (reconcile.Result, error) {
// suppress error
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Suggested change
// suppress error
// suppress error and/or
// log it and/or
// update the parent's status

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in this example, it's surprising the error. Logging or updating status are other things that could be done.

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Very nice! Looking forward to drying up state maintenance with TryCatch

@scothis scothis merged commit 919abf6 into vmware-labs:main Aug 31, 2023
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@scothis scothis deleted the flow-control branch August 31, 2023 13:27
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3 participants