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58 lines
1.9 KiB
Go
58 lines
1.9 KiB
Go
/*
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Copyright 2021 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 handler
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import (
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"sync"
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)
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// HandlerCache represents a lazy cache for generating a byte array
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// It is used to lazily marshal OpenAPI v2/v3 and lazily generate the ETag
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type HandlerCache struct {
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BuildCache func() ([]byte, error)
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once sync.Once
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bytes []byte
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err error
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}
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// Get either returns the cached value or calls BuildCache() once before caching and returning
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// its results. If BuildCache returns an error, the last valid value for the cache (from prior
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// calls to New()) is used instead if possible.
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func (c *HandlerCache) Get() ([]byte, error) {
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c.once.Do(func() {
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bytes, err := c.BuildCache()
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// if there is an error updating the cache, there can be situations where
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// c.bytes contains a valid value (carried over from the previous update)
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// but c.err is also not nil; the cache user is expected to check for this
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c.err = err
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if c.err == nil {
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// don't override previous spec if we had an error
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c.bytes = bytes
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}
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})
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return c.bytes, c.err
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}
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// New creates a new HandlerCache for situations where a cache refresh is needed.
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// This function is not thread-safe and should not be called at the same time as Get().
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func (c *HandlerCache) New(cacheBuilder func() ([]byte, error)) HandlerCache {
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return HandlerCache{
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bytes: c.bytes,
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BuildCache: cacheBuilder,
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}
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}
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