singleflight

README

Singleflight

Package singleflight provides a duplicate function call suppression mechanism.

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

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

The tailscale fork adds generics.

This fork adds contexts.

Documentation

Overview

Package singleflight provides a duplicate function call suppression mechanism.

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

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

The tailscale fork adds generics.

This fork adds contexts.

Index

• type Group
  • func (g *Group[K, V]) Do(ctx context.Context, key K, fn func(context.Context) (V, error)) (v V, err error, shared bool)
  • func (g *Group[K, V]) DoChan(ctx context.Context, key K, fn func(context.Context) (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(ctx context.Context, key K, fn func(context.Context) (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(ctx context.Context, key K, fn func(context.Context) (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.