Finalizers behavior on Exception

[ghost]

Hello, thank you for this great SDK.

I have a question about finalizers' behavior - what happens if the FinalizeAsync throws an exception? Is finalizer removed, or will finalization be re-scheduled and repeated again?

[erin-allison]

I don't have anything set up right now to properly test this, but from digging through the code, I am relatively confident that the event will be re-queued and your finalizer will be called again.

Based on the logic in FinalizerManager<TEntity>, we can see that if any of your registered IResourceFinalizer<TEntity> instances throw an exception, they will not be removed from the resource, continuing to block deletion.

dotnet-operator-sdk/src/KubeOps/Operator/Finalizer/FinalizerManager{TEntity}.cs

Lines 83 to 91 in 02bb7ec

	try
	{
	await semaphore.WaitAsync();
	entity.RemoveFinalizer(finalizer.Identifier);
	}
	finally
	{
	semaphore.Release();
	}

Tracing up the call stack to ManagedResourceController<TEntity>, we can see WatcherEvents has logic specifically to handle Finalization...

dotnet-operator-sdk/src/KubeOps/Operator/Controller/ManagedResourceController{TEntity}.cs

Lines 78 to 82 in 02bb7ec

	data => Observable.FromAsync(
	() => data.ResourceEvent == ResourceEventType.Finalizing
	? HandleResourceFinalization(data)
	: HandleResourceEvent(data),
	ThreadPoolScheduler.Instance))

... and ErroredEvents mirrors that logic as well, suggesting that the event would go back on the stack to be processed again.

dotnet-operator-sdk/src/KubeOps/Operator/Controller/ManagedResourceController{TEntity}.cs

Lines 136 to 142 in 02bb7ec

	.Select(
	data => Observable.FromAsync(
	() => data?.ResourceEvent == ResourceEventType.Finalizing
	? HandleResourceFinalization(data)
	: HandleResourceEvent(data),
	ThreadPoolScheduler.Instance))
	.Merge();

[buehler]

Perfectly summarized :-)
Be aware, that if a finalizer constantly throws exceptions (for example wrong code) this may block the deletion of resources permanently.