英文:
Must I synchronise read and write operations when doing it from different goroutines?
问题
据我所知，每个对服务器的请求都会创建一个新的goroutine。例如（可能是不正确的代码，但这个主题不是关于它的）：
package main
import "net/http"
var exampleMap map[string]string
func handlerPost(w http.ResponseWriter, r *http.Request) {
switch r.Method {
case "POST":
{
exampleMap["test"] = test // 我需要同步这个写操作吗？
}
case "GET":
{
if v, ok := exampleMap["test"]; ok { // 那么读操作呢？
fmt.Println(v)
}
}
}
}
func main() {
http.HandleFunc("/", handlerPost)
http.ListenAndServe(":8080", nil)
}
这是否意味着像这样做是不安全的，我必须使用sync.Map（例如），如果这里的map是数据库查询呢？在这种情况下我该怎么办？谢谢！
英文:
As I know, every requests to the server creates new goroutine. For ex (probably incorrect code, but this topic is not about it):
package main
import "net/http"
var exampleMap map[string]string
func handlerPost(w http.ResponseWriter, r *http.Request) {
switch r.Method {
case "POST":
{
exampleMap["test"] = test // Must I syncrhonise this writing?
}
case "GET":
{
if v, ok := exampleMap["test"] { // And what about reading?
fmt.Println(v)
}
}
}
}
func main() {
http.HandleFunc("/", handlerPost)
http.ListenAndServe(":8080", nil)
}
Does it mean that its unsafe to do it like this and I have to use sync.Map (for example), and what about if instead map here was a database queries? What can I do in this case. Thank you!
答案1
得分: 2
exampleMap在多个goroutine之间共享，因此需要对其进行同步访问。可以使用互斥锁（mutex），或者使用读写锁（RWMutex）以提高性能：
var exampleMap map[string]string
var exampleMutex sync.RWMutex
...
exampleMutex.Lock()
exampleMap["test"] = test
exampleMutex.Unlock()
...
exampleMutex.RLock()
v, ok := exampleMap["test"]
exampleMutex.RUnlock()
if ok {
...
}
请注意，以上代码是用于同步访问exampleMap的示例。
英文:
exampleMap is shared among goroutines, so you have to synchronize access to it. A mutex would do, a RWMutex would perform better:
var exampleMap map[string]string
var exampleMutex sync.RWMutex
...
exampleMutex.Lock()
exampleMap["test"] = test
exampleMutex.Unlock()
...
exampleMutex.RLock()
v, ok := exampleMap["test"]
exampleMutex.RUnlock()
if ok {
...
}
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