App Logic and Runtime Separation #402
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…capabilities via CUE and generating the App Manifest file and go type. Initial Go implementation of the manifest with the ability for the manifest data to be located in various places, starting with embedding manifest data.
…gs for admission operations.
…dalone operator app runner.
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| // AppManagedKind is a Kind and associated functionality used by an App. | ||
| type AppManagedKind struct { |
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Is there any distinction between a kind that the app manipulates vs one that it has a read-only relationship with? Is that distinction useful?
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I think the valuable distinction would be between kinds managed by the app (i.e. in the app manifest/CRDs the app author deploys) and kinds that you may want to watch/reconcile which are not managed by the app. In this case, there is no way to introduce kinds that are not managed by the app to watch/reconcile, but this is probably a good feature to introduce to simple.App.
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I've introduced simple.AppUnmanagedKind and simple.App.WatchKind(simple.AppUnmanagedKind) for establishing watchers/reconcilers on kinds which the app does not manage (this can also still be done via the AddRunnable method, but it's more cumbersome).
…le purposes to a simple.App.
…ontext as well in StandaloneOperator.Run. Introduce app.MultiRunner for a centralized place for dealing with a Runnable that runs multiple Runnables under the hood (analogous to operator.Operator).
…onfig, which is app-specific config that a provider will pass to the runner to include in app.Config when calling NewApp. Added app.SingletonRunner, which allows for multiple Run() calls without running the wrapped Runnable multiple times. Use app.SingletonRunner for running the webserver components of simple.StandaloneOperator, and invert the provider/config logic so that config is provided in NewStandaloneOperator, and Run now is passed an app.Provider.
… AppManagedKind or AppUnmanagedKind has both a Watcher and Reconciler.
…er about the functionality. CHange the signature to return an object, rather than using an http.ResponseWriter for responses, and introduce a sentinel error for a not-found route.
…d(s) when registering custom resource routes.
app/app.go
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| // should be capable of being run by an app wrapper. | ||
| type App interface { | ||
| // Validate validates the incoming request, and returns an error if validation fails | ||
| Validate(ctx context.Context, request *resource.AdmissionRequest) error |
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very nit: since we have AdmissionRequest and MutatingResponse re-declared above, should we use them here?
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Yes, we should be using them here, I completely forgot to do so 🤦 . Good catch.
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OK, implementing was a bit more work than I anticipated, but Validate and Mutate now use the app.AdmissionRequest and app.MutatingResponse. Had to introduce some new interfaces and types in simple (simple.KindValidator and its simple implementation simple.Validator, and simple.KindMutator and its implementation simple.Mutator), and then a translation in operator.Runner because k8s.WebhookServer wants the resource variants. Probably future work to make this whole chain more efficient, but for now, the API for app.App is correct, which is what matters more.
…AdmissionRequest and app.MutatingResponse types, instead of the resource.* ones. Updated simple.App to use this and introduce interfaces analogous to resource.ValidatingAdmissionController and resource.MutatingAdmissionController (simple.KindValidator and simple.KindMutator respectively), in addition to simple implementations of them analogous to resource.SimpleValidatingAdmissionController and resource.SimpleMutatingAdmissionController (simple.Validator and simple.Mutator respectively). Updated operator.Runner to cast between the resource.* and app.* variants of these types, as k8s.WebhookServer uses the resource ones.
What This PR Does / Why We Need It
This PR resolves #385 by introducing a new way to write and run apps focused around app logic implementing the interface
app.App, and runtime logic (such as a standalone operator) existing as a layer overapp.Appwhich translates runtime-specific behaviors into theapp.Appmethod calls.App Logic
App logic is now handled as implementation of the new
app.Appinterface, which describes all possible app behaviors. A default implementation, akin tosimple.Operator, exists assimple.App(created withsimple.NewApp). A user can also write a custom implementation ofapp.Appif they so wish, and it should be compatible with any runner that consumes anapp.App/app.Provider.app.Provideris an interface for usage by runners, which provides anapp.Manifestto the runner to get app capabilities, and then allows for creation of anapp.Appwith configuration sourced from the runner (such as KubeConfig, which may have varying methods by which it is loaded depending on the runner).Runtime Logic
This PR introduces only one runner,
simple.StandaloneOperator, which runs an app as a standalone operator. Combined withsimple.App, this gives users the same (and slightly more) functionality thatsimple.Operatorcurrently does. Planned in a future PR isplugin.App(or a similar name), which will run the app as a plugin and translate gRPC admission and CallResource calls into the app method calls.Codegen & Documentation
Codegen for
grafana-app-sdk component addwill be introduced in a future PR to keep this one lighter, alongside documentation and examples for writing an app in this new manner (and existing documentation will be updated to working with apps this way). This PR is focused on introducing the new functionality, and as the "old" (current) way of writing apps is still perfectly valid, documentation will be added and updated in a docs-focused PR.Other Changes
This PR also contains a drive-by fix for app manifest go codegen, as it currently improperly duplicates the
Validationfield for mutation when enabled.