Concurrency Problem - code sample

demo-1.go

package main

import "github.com/gin-gonic/gin"

func main() {
	r := gin.Default()

	quota := 1000

	r.GET("/", func(c *gin.Context) {
		c.JSON(200, gin.H{
			"remain": quota,
		})
	})

	r.GET("/use", func(c *gin.Context) {
		if quota <= 0 {
			c.JSON(400, gin.H{
				"status": "OUT OF QUOTA",
			})
		} else {
			quota--
			c.JSON(200, gin.H{
				"status": "OK",
			})
		}
	})

	r.Run()
}

demo-atomic.go

package main

import (
	"sync/atomic"
	"github.com/gin-gonic/gin"
)

func main() {
	r := gin.Default()

	var quota int32 = 1000

	r.GET("/", func(c *gin.Context) {
		c.JSON(200, gin.H{
			"remain": quota,
		})
	})

	r.GET("/use", func(c *gin.Context) {
		if atomic.LoadInt32(&quota) <= 0 {
			c.JSON(400, gin.H{
				"status": "OUT OF QUOTA",
			})
		} else {
			atomic.AddInt32(&quota, -1)
			c.JSON(200, gin.H{
				"status": "OK",
			})
		}
	})

	r.Run()
}

demo-mutex.go

package main

import (
	"sync"
	"github.com/gin-gonic/gin"
)

func main() {
	r := gin.Default()

	var quota int32 = 1000
	var lock sync.Mutex

	r.GET("/", func(c *gin.Context) {
		c.JSON(200, gin.H{
			"remain": quota,
		})
	})

	r.GET("/use", func(c *gin.Context) {
		lock.Lock()
		defer lock.Unlock()

		if quota <= 0 {
			c.JSON(400, gin.H{
				"status": "OUT OF QUOTA",
			})
		} else {
			quota--
			c.JSON(200, gin.H{
				"status": "OK",
			})
		}
	})

	r.Run()
}

test-command.sh

#download go dependency
go get -u github.com/gin-gonic/gin

#start server
go run demo-1.go

#run test - 1 concurrent
ab -n 1000 -c 1 http://localhost:8080/use

#run test - 10 concurrent
ab -n 1000 -c 10 http://localhost:8080/use

#check remain quota
curl http://localhost:8080