56d357773e
When Forget was called, we delete key associated with current call from map. When that call is done, it does delete key again, causing the same key set by other call after Forget lost. To fix it, adding a boolean value to check whether the call is forgotten, the call only does delete key if Forget is not called. Fixes golang/go#31420 Change-Id: I9708352ca3ff76c77f659916b37a496fdeb480d2 Reviewed-on: https://go-review.googlesource.com/c/sync/+/171897 Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
120 lines
3 KiB
Go
120 lines
3 KiB
Go
// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package singleflight provides a duplicate function call suppression
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// mechanism.
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package singleflight // import "golang.org/x/sync/singleflight"
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import "sync"
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// call is an in-flight or completed singleflight.Do call
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type call struct {
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wg sync.WaitGroup
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// These fields are written once before the WaitGroup is done
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// and are only read after the WaitGroup is done.
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val interface{}
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err error
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// forgotten indicates whether Forget was called with this call's key
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// while the call was still in flight.
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forgotten bool
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// These fields are read and written with the singleflight
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// mutex held before the WaitGroup is done, and are read but
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// not written after the WaitGroup is done.
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dups int
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chans []chan<- Result
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}
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// Group represents a class of work and forms a namespace in
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// which 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[string]*call // lazily initialized
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}
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// Result holds the results of Do, so they can be passed
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// on a channel.
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type Result struct {
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Val interface{}
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Err error
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Shared bool
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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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// The return value shared indicates whether v was given to multiple callers.
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func (g *Group) Do(key string, fn func() (interface{}, error)) (v interface{}, err error, shared bool) {
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g.mu.Lock()
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if g.m == nil {
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g.m = make(map[string]*call)
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}
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if c, ok := g.m[key]; ok {
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c.dups++
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g.mu.Unlock()
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c.wg.Wait()
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return c.val, c.err, true
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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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g.doCall(c, key, fn)
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return c.val, c.err, c.dups > 0
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}
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// DoChan is like Do but returns a channel that will receive the
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// results when they are ready.
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func (g *Group) DoChan(key string, fn func() (interface{}, error)) <-chan Result {
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ch := make(chan Result, 1)
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g.mu.Lock()
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if g.m == nil {
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g.m = make(map[string]*call)
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}
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if c, ok := g.m[key]; ok {
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c.dups++
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c.chans = append(c.chans, ch)
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g.mu.Unlock()
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return ch
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}
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c := &call{chans: []chan<- Result{ch}}
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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 g.doCall(c, key, fn)
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return ch
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}
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// doCall handles the single call for a key.
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func (g *Group) doCall(c *call, key string, fn func() (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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if !c.forgotten {
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delete(g.m, key)
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}
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for _, ch := range c.chans {
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ch <- Result{c.val, c.err, c.dups > 0}
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}
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g.mu.Unlock()
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}
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// Forget tells the singleflight to forget about a key. Future calls
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// to Do for this key will call the function rather than waiting for
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// an earlier call to complete.
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func (g *Group) Forget(key string) {
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g.mu.Lock()
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if c, ok := g.m[key]; ok {
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c.forgotten = true
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}
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delete(g.m, key)
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g.mu.Unlock()
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}
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