semaphore

Resizable Semaphore

A resizable semaphore for Golang.

Inspired by and possible due to https://github.com/eapache/channels.

Feature Overview

• Conforms to typical semaphore interfaces
• Semaphore can be resized, up or down, at runtime

Example

General Usage

package main

import (
	"context"
	"fmt"
	"sync"
	"time"

	"github.com/tlkamp/go-semaphore"
)

func main() {
	sem := semaphore.New(2)
	wg := &sync.WaitGroup{}

	for i := 0; i <= 10; i++ {
		err := sem.Acquire(context.Background())
		if err != nil {
			fmt.Println(err)
			return
		}

		wg.Add(1)
		go func(n int) {
			defer sem.Release()
			defer wg.Done()

			time.Sleep(3 * time.Second)
			fmt.Printf("Processed: %d\n", n)
		}(i)
	}

	wg.Wait()
	fmt.Println("Complete")
}

Resize the Semaphore

package main

import (
	"context"
	"fmt"
	"sync"
	"time"

	"github.com/tlkamp/go-semaphore"
)

func longFn(i int) {
	time.Sleep(200 * time.Millisecond)
	fmt.Printf("Processed: %d\n", i)
}

func main() {
	sem := semaphore.New(1)
	wg := &sync.WaitGroup{}

	// Set a timer and then increase the semaphore substantially
	go func() {
		time.Sleep(3 * time.Second)
		sem.Resize(10)
		fmt.Printf("===> Resized to %d\n", sem.Cap())
	}()

	for i := 0; i <= 100; i++ {
		err := sem.Acquire(context.Background())
		if err != nil {
			fmt.Println(err)
			return
		}

		wg.Add(1)
		go func(n int) {
			defer sem.Release()
			defer wg.Done()

			longFn(n)
		}(i)
	}

	wg.Wait()
	fmt.Println("Complete")
}

Contribute

Contributions are accepted in the form of issues and PRs.

PRs must have:

• Test cases
• Documentation
• Example (if applicable)