Go: Building Web Applications

Working with files

Files are a great example of areas where data consistency issues such as race conditions can lead to more permanent and catastrophic problems. Let's look at a piece of code that might continuously attempt to update a file to see where we could run into race conditions, which in turn could lead to bigger problems such as an application failing or losing data consistency:

package main

import(
  "fmt"
  "io/ioutil"
  "strconv"
  "sync"
)


func writeFile(i int) {

  rwLock.RLock();
  ioutil.WriteFile("test.txt", 
    []byte(strconv.FormatInt(int64(i),10)), 0x777)
  rwLock.RUnlock();

  writer<-true

}

var writer chan bool
var rwLock sync.RWMutex

func main() {
  
  writer = make(chan bool)

  for i:=0;i<10;i++ {
    go writeFile(i)
  }


  <-writer
  fmt.Println("Done!")
}