golang example_test 代码
文件路径：/src/sync/atomic/example_test.go
/ Copyright 2018 The Go Authors. All rights reserved.
/ Use of this source code is governed by a BSD-style
/ license that can be found in the LICENSE file.
package atomic_test
import (
"sync"
"sync/atomic"
"time"
)
func loadConfig() map[string]string {
return make(map[string]string)
}
func requests() chan int {
return make(chan int)
}
/ The following example shows how to use Value for periodic program config updates
/ and propagation of the changes to worker goroutines.
func ExampleValue_config() {
var config atomic.Value / holds current server configuration
/ Create initial config value and store into config.
config.Store(loadConfig())
go func() {
/ Reload config every 10 seconds
/ and update config value with the new version.
for {
time.Sleep(10 * time.Second)
config.Store(loadConfig())
}
}()
/ Create worker goroutines that handle incoming requests
/ using the latest config value.
for i := 0; i < 10; i++ {
go func() {
for r := range requests() {
c := config.Load()
/ Handle request r using config c.
_, _ = r, c
}
}()
}
}
/ The following example shows how to maintain a scalable frequently read,
/ but infrequently updated data structure using copy-on-write idiom.
func ExampleValue_readMostly() {
type Map map[string]string
var m atomic.Value
m.Store(make(Map))
var mu sync.Mutex / used only by writers
/ read function can be used to read the data without further synchronization
read := func(key string) (val string) {
m1 := m.Load().(Map)
return m1[key]
}
/ insert function can be used to update the data without further synchronization
insert := func(key, val string) {
mu.Lock() / synchronize with other potential writers
defer mu.Unlock()
m1 := m.Load().(Map) / load current value of the data structure
m2 := make(Map) / create a new value
for k, v := range m1 {
m2[k] = v / copy all data from the current object to the new one
}
m2[key] = val / do the update that we need
m.Store(m2) / atomically replace the current object with the new one
/ At this point all new readers start working with the new version.
/ The old version will be garbage collected once the existing readers
/ (if any) are done with it.
}
_, _ = read, insert
}