SizedWaitGroup has the same role and close to the same API as the Golang sync.WaitGroup but it adds a limit on the amount of goroutines started concurrently.
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README.md

SizedWaitGroup

GoDoc

SizedWaitGroup has the same role and API as sync.WaitGroup but it adds a limit of the amount of goroutines started concurrently.

SizedWaitGroup adds the feature of limiting the maximum number of concurrently started routines. It could for example be used to start multiples routines querying a database but without sending too much queries in order to not overload the given database.

Example

package main

import (
        "fmt"
        "math/rand"
        "time"

        "github.com/remeh/sizedwaitgroup"
)

func main() {
        rand.Seed(time.Now().UnixNano())

        // Typical use-case:
        // 50 queries must be executed as quick as possible
        // but without overloading the database, so only
        // 8 routines should be started concurrently.
        swg := sizedwaitgroup.New(8)
        for i := 0; i < 50; i++ {
                swg.Add()
                go func(i int) {
                        defer swg.Done()
                        query(i)
                }(i)
        }

        swg.Wait()
}

func query(i int) {
        fmt.Println(i)
        ms := i + 500 + rand.Intn(500)
        time.Sleep(time.Duration(ms) * time.Millisecond)
}

License

MIT

Copyright

Rémy Mathieu © 2016