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Use generics to do global cache lookup.
Signed-off-by: Nolan Brubaker <nolan@nbrubaker.com>
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| /* | ||
| Copyright 2023 The KCP Authors. | ||
| Licensed under the Apache License, Version 2.0 (the "License"); | ||
| you may not use this file except in compliance with the License. | ||
| You may obtain a copy of the License at | ||
| http://www.apache.org/licenses/LICENSE-2.0 | ||
| Unless required by applicable law or agreed to in writing, software | ||
| distributed under the License is distributed on an "AS IS" BASIS, | ||
| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| See the License for the specific language governing permissions and | ||
| limitations under the License. | ||
| */ | ||
|
|
||
| package informer | ||
|
|
||
| import ( | ||
| "github.com/kcp-dev/logicalcluster/v3" | ||
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| "k8s.io/apimachinery/pkg/api/errors" | ||
| "k8s.io/apimachinery/pkg/labels" | ||
| "k8s.io/apimachinery/pkg/runtime" | ||
| ) | ||
|
|
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| // ClusterLister is a cluster-aware Lister API. | ||
| type ClusterLister[R runtime.Object, L Lister[R]] interface { | ||
| Cluster(name logicalcluster.Name) L | ||
| } | ||
|
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| // Lister is a Lister API with generics. | ||
| type Lister[R runtime.Object] interface { | ||
| List(labels.Selector) ([]R, error) | ||
| } | ||
|
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| // FallbackListFunc is a function that returns []R from either local or global informer Listers based on a label selector. | ||
| type FallbackListFunc[R runtime.Object] func(selector labels.Selector) ([]R, error) | ||
|
|
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| // ClusterGetter is a cluster-aware Getter API. | ||
| type ClusterGetter[R runtime.Object, G Getter[R]] interface { | ||
| Cluster(name logicalcluster.Name) G | ||
| } | ||
|
|
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| // Getter is a GetAPI call with generics. | ||
| type Getter[R runtime.Object] interface { | ||
| Get(name string) (R, error) | ||
| } | ||
|
|
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| // FallbackGetFunc is a function that returns an instance of R from either local or global informer Listers based on a name. | ||
| type FallbackGetFunc[R runtime.Object] func(name string) (R, error) | ||
|
|
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| // ScopedFallbackGetFunc is a function that returns an instance of R from either local or global cluster-scoped informer Listers based on a name. | ||
| type ScopedFallbackGetFunc[R runtime.Object] func(clusterName logicalcluster.Name, name string) (R, error) | ||
|
|
||
| // NewListerWithFallback creates a new FallbackListFunc that looks up an object of type R first in the local lister, then in the global lister if no local results are found. | ||
| func NewListerWithFallback[R runtime.Object](localLister Lister[R], globalLister Lister[R]) FallbackListFunc[R] { | ||
| return func(selector labels.Selector) ([]R, error) { | ||
| r, err := localLister.List(selector) | ||
| if len(r) == 0 { | ||
| return globalLister.List(selector) | ||
| } | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return r, nil | ||
| } | ||
| } | ||
|
|
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| // NewGetterWithFallback creates a new FallbackGetFunc that gets an object of type R first looking in the local lister, then in the global lister if not found. | ||
| func NewGetterWithFallback[R runtime.Object](localGetter, globalGetter Getter[R]) FallbackGetFunc[R] { | ||
| return func(name string) (R, error) { | ||
| var r R | ||
| r, err := localGetter.Get(name) | ||
| if errors.IsNotFound(err) { | ||
| return globalGetter.Get(name) | ||
| } | ||
| if err != nil { | ||
| // r will be nil in this case | ||
| return r, err | ||
| } | ||
| return r, nil | ||
| } | ||
| } | ||
|
|
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| // NewScopedGetterWithFallback creates a new ScopedFallbackGetFunc that gets an object of type R within a given cluster path. The local lister is | ||
| // checked first, and if nothing is found, the global lister is checked. | ||
| func NewScopedGetterWithFallback[R runtime.Object, G Getter[R]](localGetter, globalGetter ClusterGetter[R, G]) ScopedFallbackGetFunc[R] { | ||
| return func(clusterName logicalcluster.Name, name string) (R, error) { | ||
| var r R | ||
| r, err := localGetter.Cluster(clusterName).Get(name) | ||
| if errors.IsNotFound(err) { | ||
| return globalGetter.Cluster(clusterName).Get(name) | ||
| } | ||
| if err != nil { | ||
| return r, err | ||
| } | ||
| return r, nil | ||
| } | ||
| } |
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