worker_pool_example.go

/*
* A very simple example of having a pool of workers perform jobs
* from the same channel. Simulates a situation where we have a long running
* process such as web server that receives requests and then posts the payloads
* to workers.
*/
package main

import (
  "bufio"
  "fmt"
  "os"
  "strconv"
  "time"
)

// worker-function for polling more jobs and performing them
// workerID: id to separate workers output from each other
// jobs: a channel of string, the worker polls this channel for more jobs
//    using <- means that this channel is receive only, we can't post back to this channel
//    from this function
func worker(workerID int, jobs <-chan string) {

  // use loop to keep reading jobs from the channel
  // until it is closed (the magic is in the use of ´range´)
  for job := range jobs {
    // the "job" is to print out values we receive
    fmt.Println("\njob(" + strconv.Itoa(workerID) + "): " + job)

    // simulate a long running job
    if workerID == 3 {
      time.Sleep(time.Second * 3)
    }
  }

}

func main() {

  // channel to post jobs into
  jobs := make(chan string)

  // create a pool of workers (goroutines)
  for w := 1; w <= 3; w++ {
    go worker(w, jobs)
  }

  // read user input
  reader := bufio.NewReader(os.Stdin)

  for {
    text, _ := reader.ReadString('\n')

    // post a job into jobs-channel
    jobs <- text
  }

}