107 lines
2.1 KiB
Go
107 lines
2.1 KiB
Go
// Package singleflight based on github.com/golang/groupcache/singleflight
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package singleflight
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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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}
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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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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 sure that
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// only one execution is in-flight for a given key at a time. If a duplicate
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// comes in, the duplicate caller waits for the original to complete and
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// receives the same results.
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func (g *Group) Do(key interface{}, fn func() interface{}) interface{} {
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g.mu.Lock()
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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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c.wg.Wait()
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return c.val
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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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c.val = 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
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}
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// DoAsync used instead of Do, when there is not need to wait for result. It
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// behaves like go { Group.Do(key, fn) }(), but doesn't create goroutine when
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// there is another execution for given key in-flight.
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func (g *Group) DoAsync(key interface{}, fn func() interface{}) {
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g.mu.Lock()
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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 _, ok := g.m[key]; ok {
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g.mu.Unlock()
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return
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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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go func() {
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c.val = 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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}()
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}
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// Call represents single deduplicated function call.
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type Call struct {
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mu sync.Mutex
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callState *callState
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}
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type callState struct {
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wg sync.WaitGroup
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val interface{}
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}
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func (c *Call) Do(fn func() interface{}) interface{} {
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c.mu.Lock()
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if c.callState != nil {
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callState := c.callState
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c.mu.Unlock()
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callState.wg.Wait()
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return callState.val
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}
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c.callState = &callState{}
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c.callState.wg.Add(1)
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c.mu.Unlock()
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res := fn()
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c.mu.Lock()
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c.callState.val = res
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c.callState.wg.Done()
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c.callState = nil
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c.mu.Unlock()
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return res
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}
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