Golang Web应用程序中的同步

Question

I'm writing a golang web application. The web application accesses the file system (reading and writing) and an sqlite3 database file.

Question 1: How can I synchronize file system access in Go?

type DataObject struct {
  data []byte
}

func (*d DataObject) Write() {
   //
   // Synchronization ?
   //
   ioutil.WriteFile("file.name", d.data, 0644)
   //
   // Stop synchronization ?
   //
}

---

Question 2: Do I need to synchronize sqlite3 database file access?

type SqlObject struct {
  sqldata string
}

func (*s SqlObject) Store() error {
  //
  // Open the file, do I need some sort of synchronization?
  //
  con, err := sqlite.Open("database/datafile.db")
  if err != nil {
    return err
  }
  defer con.Close()

  err = con.Exec("INSERT INTO data(sqldata) values(?)", s.sqldata)
  if err != nil {
    return err
  }
  return nil
}

I'm using the gosqlite3 driver (http://code.google.com/p/gosqlite/).

Answer 1

For files it depends on your application. If you only have one goroutine writing to the file, you shouldn't need to. If more than one then it depends:

If you are coordinating between different processes (programs) you can use flock (and it probably won't be fun).

If you are coordinating multiple goroutines in your program you can use mutexes or you can see if you can re-organize the program so just one routine writes to the file and the others send updates via channels.

For SQLite I believe the easiest way would be to just keep one sqlite connection open and use that from the various goroutines; though it does support multiple processes having it open at once and if your system does many concurrent reads that might be faster (it uses a global lock for writing).