74 lines
1.9 KiB
Go
74 lines
1.9 KiB
Go
/*
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Copyright 2014 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package volume
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import (
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"sync"
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"sync/atomic"
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)
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var _ MetricsProvider = &cachedMetrics{}
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// cachedMetrics represents a MetricsProvider that wraps another provider and
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// caches the result.
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type cachedMetrics struct {
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wrapped MetricsProvider
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resultError error
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resultMetrics *Metrics
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once cacheOnce
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}
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// NewCachedMetrics creates a new cachedMetrics wrapping another
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// MetricsProvider and caching the results.
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func NewCachedMetrics(provider MetricsProvider) MetricsProvider {
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return &cachedMetrics{wrapped: provider}
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}
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// GetMetrics runs the wrapped metrics provider's GetMetrics methd once and
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// caches the result. Will not cache result if there is an error.
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// See MetricsProvider.GetMetrics
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func (md *cachedMetrics) GetMetrics() (*Metrics, error) {
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md.once.cache(func() error {
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md.resultMetrics, md.resultError = md.wrapped.GetMetrics()
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return md.resultError
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})
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return md.resultMetrics, md.resultError
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}
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// Copied from sync.Once but we don't want to cache the results if there is an
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// error
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type cacheOnce struct {
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m sync.Mutex
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done uint32
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}
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// Copied from sync.Once but we don't want to cache the results if there is an
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// error
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func (o *cacheOnce) cache(f func() error) {
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if atomic.LoadUint32(&o.done) == 1 {
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return
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}
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// Slow-path.
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o.m.Lock()
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defer o.m.Unlock()
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if o.done == 0 {
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err := f()
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if err == nil {
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atomic.StoreUint32(&o.done, 1)
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}
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}
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}
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