README
¶
semgroup
semgroup provides a simple wrapper around an error group
that adds the ability to limit the maximum number of in-flight goroutines working on a group of tasks
via a weighted semaphore. The API is exactly the same
as the errgroup package.
Getting Started
Get the latest version of the package with go get
go get -u github.com/mwalto7/semgroup
Example
package main
import (
"context"
"fmt"
"log"
"runtime"
"time"
"github.com/mwalto7/semgroup"
)
func main() {
// Create a new group with a maximum of 10 in-flight goroutines.
sg, ctx := semgroup.WithContext(context.Background(), 10)
// At most 10 goroutines will print "subtask <i>" between sleeps.
for i := 0; i < 100; i++ {
i := i
sg.Go(func() error {
select {
case <-ctx.Done():
return ctx.Err()
default:
fmt.Printf("subtask %d\n", i)
}
time.Sleep(2 * time.Second)
return nil
})
}
// Wait for all goroutines to finish, propagating the first non-nil error (if-any).
if err := sg.Wait(); err != nil {
log.Fatal(err)
}
}
Documentation
¶
Overview ¶
Package semgroup provides a modified errgroup.Group with the ability to limit the maximum concurrent access of resources for groups of goroutines working on subtasks of a common task.
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Group ¶
type Group struct {
// contains filtered or unexported fields
}
Group is an errgroup.Group combined with a semaphore. The maximum number of in-flight goroutines is equal to the weight of the semaphore.
A zero Group is invalid. Use WithContext to initialize a Group.
Example ¶
package main
import (
"context"
"fmt"
"log"
"time"
"github.com/mwalto7/semgroup"
)
func main() {
// Create a new group with a maximum of 10 in-flight goroutines.
sg, ctx := semgroup.WithContext(context.Background(), 10)
// At most 10 goroutines will print "subtask <i>" between sleeps.
for i := 0; i < 100; i++ {
i := i
sg.Go(func() error {
select {
case <-ctx.Done():
return ctx.Err()
default:
fmt.Printf("subtask %d\n", i)
}
time.Sleep(2 * time.Second)
return nil
})
}
// Wait for all goroutines to finish, propagating the first non-nil error (if-any).
if err := sg.Wait(); err != nil {
log.Fatal(err)
}
}
Output:
func WithContext ¶
WithContext returns a new Group with a weighted semaphore with weight n and an associated Context derived from ctx.
If the given Context is nil, context.Background is used.
If the given semaphore weight n is less than or equal to zero, runtime.NumCPU()*2 is used.
func (*Group) Go ¶
Go blocks until a semaphore is acquired, then calls the given function in a new goroutine. If a non-nil error is returned when acquiring the semaphore, the error is returned and the group is cancelled.
See errgroup for details on error handling and propagation.
Source Files