semaphore

Package semaphore is a Go library that implements a semaphore for controlling the concurrency of workloads. Using a buffered channel, this package provides a safe way for multiple goroutines to request and return semaphore permits.

For those not familiar with the concept of a semaphore, it allows you to control the access to a particular resource (or particular number of resources). A common use case is to limit the number of concurrent threads permitted to process work, to avoid overcomitting the resources of a system. More details (historical and applied) about semaphores can be found here.

License

This package is licensed under the permissive MIT License.

Contributions

Contributions back to this project are more than welcomed. To request a change please issue a pull request from a fork of this repo, and be sure to include details about the change in your commit message.

Installation

Until go dep is in wider utilization:

go get -u github.com/theckman/semaphore

Usage

The package uses three method for working with semaphores: Acquire(), Release(), and Close(). Detailed usage information can be discovered via GoDoc.

Here is a quick overview of using this package:

import "github.com/theckman/semaphore"

/* ... */

sema, err := semaphore.New(2)
if err != nil {
	// handle error  
}

for i := 0; i < 10; i++ {
	// blocks until semaphore permit is given
	// or until semaphore has Close() called
	err := sema.Acquire()
	if err != nil {
		// lock acquistion failed (i.e., semaphore is no longer usable)
		panic("semaphore in unexpected state")
	}
    
	// lock acquired, spin-off work
	go func() {
		time.Sleep(time.Second * 3)
		sema.Release()
	}()
}

/* wait for work to finish... */

sema.Close()