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82 lines
2.1 KiB
82 lines
2.1 KiB
package gcache |
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/* |
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Copyright 2012 Google Inc. |
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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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// This module provides a duplicate function call suppression |
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// mechanism. |
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import "sync" |
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// call is an in-flight or completed Do call |
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type call struct { |
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wg sync.WaitGroup |
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val interface{} |
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err error |
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} |
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// Group represents a class of work and forms a namespace in which |
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// units of work can be executed with duplicate suppression. |
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type Group struct { |
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cache Cache |
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mu sync.Mutex // protects m |
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m map[interface{}]*call // lazily initialized |
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} |
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// Do executes and returns the results of the given function, making |
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// sure that only one execution is in-flight for a given key at a |
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// time. If a duplicate comes in, the duplicate caller waits for the |
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// original to complete and receives the same results. |
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func (g *Group) Do(key interface{}, fn func() (interface{}, error), isWait bool) (interface{}, bool, error) { |
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g.mu.Lock() |
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v, err := g.cache.get(key, true) |
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if err == nil { |
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g.mu.Unlock() |
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return v, false, nil |
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} |
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if g.m == nil { |
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g.m = make(map[interface{}]*call) |
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} |
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if c, ok := g.m[key]; ok { |
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g.mu.Unlock() |
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if !isWait { |
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return nil, false, KeyNotFoundError |
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} |
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c.wg.Wait() |
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return c.val, false, c.err |
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} |
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c := new(call) |
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c.wg.Add(1) |
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g.m[key] = c |
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g.mu.Unlock() |
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if !isWait { |
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go g.call(c, key, fn) |
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return nil, false, KeyNotFoundError |
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} |
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v, err = g.call(c, key, fn) |
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return v, true, err |
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} |
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func (g *Group) call(c *call, key interface{}, fn func() (interface{}, error)) (interface{}, error) { |
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c.val, c.err = fn() |
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c.wg.Done() |
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g.mu.Lock() |
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delete(g.m, key) |
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g.mu.Unlock() |
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return c.val, c.err |
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}
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