singleflight

Documentation

Overview

Package singleflight provides a duplicate function call suppression mechanism.

This is a Tailscale fork of Go's singleflight package which has had several homes in the past:

• https://github.com/golang/go/commit/61d3b2db6292581fc07a3767ec23ec94ad6100d1
• https://github.com/golang/groupcache/tree/master/singleflight
• https://pkg.go.dev/golang.org/x/sync/singleflight

This fork adds generics.

Index

• type Group
  • func (g *Group[K, V]) Do(key K, fn func() (V, error)) (v V, err error, shared bool)
  • func (g *Group[K, V]) DoChan(key K, fn func() (V, error)) <-chan Result[V]
  • func (g *Group[K, V]) Forget(key K)
• type Result

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.

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.