singleflight

Documentation

Overview

Package singleflight provides a duplicate function call suppression mechanism.

Index

• type Group
  • func (g *Group) Do(key string, fn func() (interface{}, error)) (v interface{}, err error, shared bool)
  • func (g *Group) DoChan(key string, fn func() (interface{}, error)) (<-chan Result, bool)
  • func (g *Group) ForgetUnshared(key string) bool
• type Result

Types

type Group

type Group 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) Do

func (g *Group) Do(key string, fn func() (interface{}, error)) (v interface{}, 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) DoChan

func (g *Group) DoChan(key string, fn func() (interface{}, error)) (<-chan Result, bool)

DoChan is like Do but returns a channel that will receive the results when they are ready. The second result is true if the function will eventually be called, false if it will not (because there is a pending request with this key).

func (*Group) ForgetUnshared

func (g *Group) ForgetUnshared(key string) bool

ForgetUnshared tells the singleflight to forget about a key if it is not shared with any other goroutines. Future calls to Do for a forgotten key will call the function rather than waiting for an earlier call to complete. Returns whether the key was forgotten or unknown--that is, whether no other goroutines are waiting for the result.

type Result

type Result struct {
	Val    interface{}
	Err    error
	Shared bool
}

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