英文:
How to update a function's value once it's been called in golang
问题
我正在处理一个系统，在该系统中，我必须限制来自特定IP的并发连接。一旦建立连接，会执行一些步骤，然后将其关闭，以便可以建立其他连接。下面是我正在更新特定变量值的代码。
代码链接 - http://tpcg.io/_SQZEEX
package main
import "fmt"
var addresses = make([]string, 0)
func count(rAddr string, slice *[]string) map[string]int {
dict := make(map[string]int)
*slice = append(*slice, rAddr)
for _, a := range *slice {
dict[a]++
}
return dict
}
func listen() int {
var rAddr string
rAddr = "1.1.1.2"
number_of_addresses := count(rAddr, &addresses)
var v int
for k, v := range number_of_addresses {
fmt.Println(k, "value is", v)
if v > 0 {
v--
fmt.Println(k, "decreased value is", v)
}
}
return v
}
func main() {
listen()
listen()
}
在再次调用函数时，"v"变量的值没有刷新，输出如下：
1.1.1.2 value is 1
1.1.1.2 decreased value is 0
1.1.1.2 value is 2
1.1.1.2 decreased value is 1
期望的输出是：
1.1.1.2 value is 1
1.1.1.2 decreased value is 0
1.1.1.2 value is 1
1.1.1.2 decreased value is 0
我应该怎么做才能在每次减少值时更新它？我理解值是刷新的，但没有发送回count函数。如何实现这一点？
英文:
I am working on a system where I have to limit concurrent connections from a particular IP. Once a connection is made, some steps are performed and then it is dropped so that other connections can be made. Below is the code where I am updating the value of a particular variable.
Link for code - http://tpcg.io/_SQZEEX
package main
import "fmt"
var addresses = make([]string, 0)
func count(rAddr string, slice *[]string) map[string]int {
dict := make(map[string]int)
*slice = append(*slice, rAddr)
for _, a := range *slice {
dict[a]++
}
return dict
}
func listen() int {
var rAddr string
rAddr = "1.1.1.2"
number_of_addresses:=count(rAddr ,&addresses)
var v int
for k, v := range number_of_addresses {
fmt.Println(k, "value is", v)
if (v > 0) {
v--
fmt.Println(k, "decreased value is", v)
}
}
return v
}
func main() {
listen()
listen()
}
Upon calling the function again, the values are not refreshing for the "v" variable and the output is as below
1.1.1.2 value is 1
1.1.1.2 decreased value is 0
1.1.1.2 value is 2
1.1.1.2 decreased value is 1
Expected output:
1.1.1.2 value is 1
1.1.1.2 decreased value is 0
1.1.1.2 value is 1
1.1.1.2 decreased value is 0
What could I do so that the value is updated each time it is decreased. I understand that the value is refreshed but not sent back to the count function. How can this be achieved
答案1
得分: 1
根据我的评论，重构代码以通过map来跟踪IP地址，即使用map[string]int来跟踪使用情况。
以下是一个基本的实现示例：
// 通过map来跟踪唯一的地址：
// - 键：IP地址的字符串形式
// - 值：使用计数
var (
usageMap = make(map[string]int) //
l sync.Mutex // 确保对map的并发访问是同步的
)
func modifyAddr(addr string, delta int) int {
l.Lock()
defer l.Unlock()
usageMap[addr] += delta
return usageMap[addr]
}
func incAddr(addr string) int { return modifyAddr(addr, 1) }
func decAddr(addr string) int { return modifyAddr(addr, -1) }
使用示例：
const maxConcurrentUsage = 20
func listen() {
rAddr := "1.1.1.2"
usage := incAddr(rAddr)
defer decAddr(rAddr)
if usage > maxConcurrentUsage {
log.Printf("超过最大并发使用量（%d）的地址：%q", maxConcurrentUsage, rAddr)
return
}
// 处理逻辑放在这里
}
你可以在以下链接中查看代码的运行示例：https://go.dev/play/p/Jvx8l4F9OE8
英文:
Per my comments, refactor to track IP addresses via a map i.e. a map[string]int to track usage.
A basic implementation to get you started:
// track unique addresses via a map:
// - key: string of the IP address
// - value: usage count
var (
usageMap = make(map[string]int) //
l sync.Mutex // ensure concurrent access to map is synchronized
)
func modifyAddr(addr string, delta int) int {
l.Lock()
defer l.Unlock()
usageMap[addr] += delta
return usageMap[addr]
}
func incAddr(addr string) int { return modifyAddr(addr, 1) }
func decAddr(addr string) int { return modifyAddr(addr, -1) }
and to use:
const maxConcurrentUsage = 20
func listen() {
rAddr := "1.1.1.2"
usage := incAddr(rAddr)
defer decAddr(rAddr)
if usage > maxConcurrentUsage {
log.Printf("maximum concurrent usage exceeded (%d) for address: %q", maxConcurrentUsage, rAddr)
return
}
// handler logic goes here
}
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