英文:
Is it possible to limit how many goroutines run per second?
问题
我有一个URL列表，我需要使用goroutine并发地发送HTTP请求。有没有办法检查和限制每秒发送的HTTP请求数量？
英文:
I have a list of URLs that I need to use goroutine to fire off HTTP requests concurrently. Is there anyway to check and limit how many of those HTTP requests are sent per second?
答案1
得分: 13
这是一个使用Go语言编写的简单版本，它是Leaky Bucket算法的一种改编，使用了通道和goroutine。在发出请求之前，从rate通道接收一个令牌将检查速率，并在速率限制器为空时阻塞。
// 创建一个带缓冲的通道。
// 通道的容量是最大的突发请求数。
rate := make(chan struct{}, 10)
go func() {
ticker := time.NewTicker(100 * time.Millisecond)
for range ticker.C {
rate <- struct{}{}
}
}()
由于一系列请求的时间超过了平均速率，最终会变成并发请求，因此您可能还需要限制并发性。您可以添加第二个通道作为信号量，在发出请求之前添加一个令牌，并在请求完成后将其删除。
// 将并发限制为5
semaphore := make(chan struct{}, 5)
// 在请求函数中
semaphore <- struct{}{}
defer func() {
<-semaphore
}()
这里有一个稍微完整一些的示例：
https://play.golang.org/p/ZrTPLcdeDF
英文:
A very simple version of this in Go would be an adaptation of a Leaky Bucket algorithm, using a channel and a goroutine. Receiving a token from the rate channel before making a request will check the rate and block if the rate limiter is empty.
// create a buffered channel.
// The capacity of the channel is maximum burst that can be made.
rate := make(chan struct{}, 10)
go func() {
ticker := time.NewTicker(100 * time.Millisecond)
for range ticker.C {
rate <- struct{}{}
}
}()
Since a series of requests that take longer than the average rate will end up being concurrent, you may need to limit concurrency too. You can add a second channel as a semaphore, adding a token to the semaphore before making a request, and removing it when it's complete.
// limit concurrency to 5
semaphore := make(chan struct{}, 5)
// in request function
semaphore <- struct{}{}
defer func() {
<-semaphore
}()
A slightly more complete example is here:
答案2
得分: -1
这是一个简单的包，可以帮助你限制同时运行的goroutine数量。请查看https://github.com/zenthangplus/goccm
示例：
package main
import (
"fmt"
"goccm"
"time"
)
func main() {
// 限制同时运行的goroutine数量为3个。
c := goccm.New(3)
for i := 1; i <= 10; i++ {
// 在任何goroutine之前都必须调用此函数
c.Wait()
go func(i int) {
fmt.Printf("Job %d is running\n", i)
time.Sleep(2 * time.Second)
// 当goroutine完成时必须调用此函数
// 或者你可以在goroutine的顶部使用`defer c.Done()`
c.Done()
}(i)
}
// 在关闭主程序后，必须调用此函数以确保所有goroutine都已完成
c.WaitAllDone()
}
英文:
Here is the simple package to help you limit the number of goroutines that are allowed to run concurrently. Please check https://github.com/zenthangplus/goccm
Example:
package main
import (
"fmt"
"goccm"
"time"
)
func main() {
// Limit 3 goroutines to run concurrently.
c := goccm.New(3)
for i := 1; i <= 10; i++ {
// This function have to call before any goroutine
c.Wait()
go func(i int) {
fmt.Printf("Job %d is running\n", i)
time.Sleep(2 * time.Second)
// This function have to when a goroutine has finished
// Or you can use `defer c.Done()` at the top of goroutine.
c.Done()
}(i)
}
// This function have to call to ensure all goroutines have finished
// after close the main program.
c.WaitAllDone()
}
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