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Lazily initialize localPodInformer in a more readable way
Instead of checking various conditions to determine whether localPodInformer should be initialized, which is error-prone and looks ugly, this patch adds a Generic interface for lazy evaluation and uses it to initialize localPodInformer when it's necessary. Signed-off-by: Quan Tian <qtian@vmware.com>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,62 @@ | ||
| // Copyright 2023 Antrea 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 lazy | ||
|
|
||
| import ( | ||
| "sync" | ||
| "sync/atomic" | ||
| ) | ||
|
|
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| // Lazy defers the evaluation of getter until it's accessed the first access. | ||
| type Lazy[T any] interface { | ||
| // Get returns the value, evaluate it if necessary. | ||
| Get() T | ||
| // Evaluated returns whether the value has been evaluated or not. | ||
| Evaluated() bool | ||
| } | ||
|
|
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| type lazy[T any] struct { | ||
| getter func() T | ||
| // res is the cached result. | ||
| res T | ||
| done uint32 | ||
| m sync.Mutex | ||
| } | ||
|
|
||
| // New returns a new lazily evaluated value. The getter is executed only when it's accessed the first access. | ||
| func New[T any](getter func() T) Lazy[T] { | ||
| return &lazy[T]{getter: getter} | ||
| } | ||
|
|
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| func (l *lazy[T]) Get() T { | ||
| if atomic.LoadUint32(&l.done) == 0 { | ||
| return l.doSlow() | ||
| } | ||
| return l.res | ||
| } | ||
|
|
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| func (l *lazy[T]) doSlow() T { | ||
| l.m.Lock() | ||
| defer l.m.Unlock() | ||
| if l.done == 0 { | ||
| defer atomic.StoreUint32(&l.done, 1) | ||
| l.res = l.getter() | ||
| } | ||
| return l.res | ||
| } | ||
|
|
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| func (l *lazy[T]) Evaluated() bool { | ||
| return atomic.LoadUint32(&l.done) == 1 | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,48 @@ | ||
| // Copyright 2023 Antrea 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 lazy | ||
|
|
||
| import ( | ||
| "testing" | ||
|
|
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| "github.com/stretchr/testify/assert" | ||
| ) | ||
|
|
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| type foo struct{} | ||
|
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| func TestLazy(t *testing.T) { | ||
| var called int | ||
| lazyFoo := New(func() *foo { | ||
| called++ | ||
| return &foo{} | ||
| }) | ||
| assert.False(t, lazyFoo.Evaluated()) | ||
| assert.Equal(t, 0, called) | ||
|
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| ch := make(chan *foo, 10) | ||
| for i := 0; i < 10; i++ { | ||
| go func() { | ||
| ch <- lazyFoo.Get() | ||
| }() | ||
| } | ||
| // Got the first result. | ||
| foo := <-ch | ||
| assert.True(t, lazyFoo.Evaluated()) | ||
| // Got the rest 9 results, all of them should reference the same object. | ||
| for i := 1; i < 10; i++ { | ||
| assert.Same(t, foo, <-ch) | ||
| } | ||
| assert.Equal(t, 1, called, "The getter should only be called exactly once") | ||
| } |