stateful-goroutines.go

package main

import (
  "fmt"
  "math/rand"
  "sync/atomic"
  "time"
)

type readOp struct {
  key int
  resp chan int
}

type writeOp struct {
  key int
  val int
  resp chan bool
}

func main() {
  var ops int64 = 0

  reads := make(chan *readOp)
  writes := make(chan *writeOp)

  go func() {
    var state = make(map[int]int)
    for {
      select {
      case read := <-reads:
        read.resp <- state[read.key]
      case write := <-writes:
        state[write.key] = write.val
        write.resp <- true
      }
    }
  }()

  for r := 0; r < 100; r++ {
    go func() {
      for {
        read := &readOp{
          key: rand.Intn(5),
          resp: make(chan int)}
        reads <- read
        <-read.resp
        atomic.AddInt64(&ops, 1)
      }
    }()
  }

  for w := 0; w < 10; w++ {
    go func() {
      for {
        write := &writeOp{
          key: rand.Intn(5),
          val: rand.Intn(100),
          resp: make(chan bool)}
        writes <- write
        <-write.resp
        atomic.AddInt64(&ops, 1)
      }
    }()
  }

  time.Sleep(time.Second)

  opsFinal := atomic.LoadInt64(&ops)
  fmt.Println("ops:", opsFinal)
}