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singleflight

package
v7.0.101 Latest Latest
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Published: May 1, 2026 License: Apache-2.0 Imports: 6 Imported by: 0

Documentation

Overview

Package singleflight provides a duplicate function call suppression mechanism. This is forked to provide type safety and have non-string keys.

Index

Examples

Constants

This section is empty.

Variables

This section is empty.

Functions

This section is empty.

Types

type Group

type Group[K comparable, V any] struct {
	// contains filtered or unexported fields
}

Group represents a class of work and forms a namespace in which units of work can be executed with duplicate suppression.

Example
g := new(Group[string, any])

block := make(chan struct{})
res1c := g.DoChan("key", func() (any, error) {
	<-block
	return "func 1", nil
})
res2c := g.DoChan("key", func() (any, error) {
	<-block
	return "func 2", nil
})
close(block)

res1 := <-res1c
res2 := <-res2c

// Results are shared by functions executed with duplicate keys.
fmt.Println("Shared:", res2.Shared)
// Only the first function is executed: it is registered and started with "key",
// and doesn't complete before the second function is registered with a duplicate key.
fmt.Println("Equal results:", res1.Val.(string) == res2.Val.(string))
fmt.Println("Result:", res1.Val)
Output:
Shared: true
Equal results: true
Result: func 1

func (*Group[K, V]) Do

func (g *Group[K, V]) Do(key K, fn func() (V, error)) (v V, err error, shared bool)

Do executes and returns the results of the given function, making sure that only one execution is in-flight for a given key at a time. If a duplicate comes in, the duplicate caller waits for the original to complete and receives the same results. The return value shared indicates whether v was given to multiple callers.

func (*Group[K, V]) DoChan

func (g *Group[K, V]) DoChan(key K, fn func() (V, error)) <-chan Result[V]

DoChan is like Do but returns a channel that will receive the results when they are ready.

The returned channel will not be closed.

func (*Group[K, V]) Forget

func (g *Group[K, V]) Forget(key K)

Forget tells the singleflight to forget about a key. Future calls to Do for this key will call the function rather than waiting for an earlier call to complete.

type Result

type Result[V any] struct {
	Val    V
	Err    error
	Shared bool
}

Result holds the results of Do, so they can be passed on a channel.

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