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@tylerb tylerb/main.go
Last active Jul 18, 2019

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Simulate io blocking
// All material is licensed under the Apache License Version 2.0, January 2004
// This sample program demonstrates how the logger package works.
package main
import (
type device struct {
blocking int32
toggle int32
// toggleBlocking will toggle the blocking state of this device
func (d *device) toggleBlocking() {
toggle := 1 - d.toggle
atomic.CompareAndSwapInt32(&d.blocking, d.toggle, toggle)
d.toggle = toggle
// wait will wait until the device is ready for use
func (d *device) wait() {
for atomic.LoadInt32(&d.blocking) == 1 {
time.Sleep(100 * time.Millisecond)
// writer allows us to mock a writer we write logs to.
type writer struct {
d *device
// Write implements the io.Writer interface.
func (w *writer) Write(p []byte) (n int, err error) {
return len(p), nil
func main() {
// Number of goroutines that will be writing logs.
const grs = 10
// Create a logger value with a buffer of capacity
// for each goroutine that will be logging.
var d device
w := writer{d: &d}
l := log.New(&w, "prefix", 0)
// Generate goroutines, each writing to disk.
for i := 0; i < grs; i++ {
go func(id int) {
for {
l.Println(fmt.Sprintf("%d: log data", id))
time.Sleep(100 * time.Millisecond)
// We want to control the simulated disk blocking. Capture
// interrupt signals to toggle device issues. Use <ctrl> z
// to kill the program.
sigChan := make(chan os.Signal, 1)
signal.Notify(sigChan, os.Interrupt)
for {
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