remeh / sizedwaitgroup

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.

SizedWaitGroup

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

sizedwaitgroup's Issues

errgroup

Am I right in thinking the use case here is very similar to golang.org/x/sync/errgroup ?

If so, it would be good to add something to the README that mentions why someone might use this library instead of errgroup.

Changing size

Is it possible to change the size of an SizedWaitGroup which is already in use?

LICENSE file would help adoption

This is a nice piece of code. It would be easier to include/reference in other projects if it had a LICENSE file with the MIT license in it. Lawyers get grumpy about these things.

?? rand ??

You initialize rand but you don't use it.
Is it used by sync ? Why ?

An inappropriate use of `break-select`

I noticed a break-select in sizewaitgroup.go, which was used in AddWithContext Method, but break keyword can not jump out of the select in Golang. Although it looks like properly worked in this method, but it`s still confusing and misunderstanding.

Option to increment, decrement by custom amounts

For my applications, it would be helpful to be able to Add(n) and Done(n), rather than having to do this with tons of individual Add(), Done() calls.