abiosoft / semaphore

Wrapping sync.Mutex for familiar semaphore api

semaphore

Semaphore in Go

Usage

Initiate

import "github.com/abiosoft/semaphore"
...
sem := semaphore.New(5) // new semaphore with 5 permits

Acquire

sem.Acquire() // one
sem.AcquireMany(n) // multiple
sem.AcquireWithin(n, time.Second * 5) // timeout after 5 sec
sem.AcquireContext(ctx, n) // acquire with context

Release

sem.Release() // one
sem.ReleaseMany(n) // multiple

documentation

http://godoc.org/github.com/abiosoft/semaphore

semaphore's Issues

data race when running tests

Run with "go test -race ./..."

==================
WARNING: DATA RACE
Read at 0x00c4200742d8 by goroutine 7:
  github.com/kevinburke/semaphore.(*Semaphore).Release()
      /Users/kevin/src/github.com/kevinburke/semaphore/semaphore.go:95 +0xde
  github.com/kevinburke/semaphore.(*Semaphore).ReleaseMany()
      /Users/kevin/src/github.com/kevinburke/semaphore/semaphore.go:104 +0x61
  github.com/kevinburke/semaphore.aq()
      /Users/kevin/src/github.com/kevinburke/semaphore/semaphore_test.go:44 +0x37e

Previous write at 0x00c4200742d8 by goroutine 12:
  github.com/kevinburke/semaphore.(*Semaphore).AcquireMany()
      /Users/kevin/src/github.com/kevinburke/semaphore/semaphore.go:57 +0x103
  github.com/kevinburke/semaphore.aq()
      /Users/kevin/src/github.com/kevinburke/semaphore/semaphore_test.go:41 +0x1d9

Goroutine 7 (running) created at:
  github.com/kevinburke/semaphore.Test()
      /Users/kevin/src/github.com/kevinburke/semaphore/semaphore_test.go:18 +0xae
  testing.tRunner()
      /Users/kevin/go/src/testing/testing.go:746 +0x16c

Goroutine 12 (running) created at:
  github.com/kevinburke/semaphore.Test()
      /Users/kevin/src/github.com/kevinburke/semaphore/semaphore_test.go:18 +0xae
  testing.tRunner()
      /Users/kevin/go/src/testing/testing.go:746 +0x16c

Add a license

A potential race condition

Acquire is ch <- 1 and release is <- ch. According to the Memory Model, there is no guarantee that a buffered channel receiving happens before the corresponding sending.
So I think the Acquire is <-ch while release is ch <- 1.

AcquireWithin should take a context.Context

It would be easy enough to wait for either ctx.Done() or for a resource to become available.