waitgroup

func (*WaitGroup) Add ¶

func (wg *WaitGroup) Add(key uint64)

(*WaitGroup).Add add adds a new caller or if the caller exists increment dups with key.

func (*WaitGroup) Done ¶

func (wg *WaitGroup) Done(key uint64)

(*WaitGroup).Done done cancels the group context or if the caller dups more then zero, decrements the dups with key.

func (*WaitGroup) Get ¶

func (wg *WaitGroup) Get(key uint64) int

(*WaitGroup).Get get return count of dups with key.

func (*WaitGroup) Join ¶ added in v1.6.4

func (wg *WaitGroup) Join(key uint64) <-chan struct{}

Join atomically decides leadership for key. It returns nil and registers the caller as the leader (caller must call Done when finished). If a leader already exists, Join returns a channel that closes when the leader finishes; followers must NOT call Done — they never registered as a participant, so calling Done would either over-decrement the dup counter or cancel the leader's context out from under it.

This API closes the Wait-then-Add race in the older Wait/Add sequence: two simultaneous first callers both saw "no leader" and both became leaders, so the dedup didn't actually dedup.

func (*WaitGroup) Wait ¶

func (wg *WaitGroup) Wait(key uint64)

(*WaitGroup).Wait wait blocks until WaitGroup context cancelled or timedout with key.