mirror of https://github.com/minio/minio.git
133 lines
3.5 KiB
Go
133 lines
3.5 KiB
Go
/*
|
|
* MinIO Cloud Storage, (C) 2017 MinIO, Inc.
|
|
*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*/
|
|
|
|
package errgroup
|
|
|
|
import (
|
|
"context"
|
|
"sync"
|
|
"sync/atomic"
|
|
)
|
|
|
|
// A Group is a collection of goroutines working on subtasks that are part of
|
|
// the same overall task.
|
|
//
|
|
// A zero Group can be used if errors should not be tracked.
|
|
type Group struct {
|
|
wg sync.WaitGroup
|
|
bucket chan struct{}
|
|
errs []error
|
|
firstErr int64
|
|
cancel context.CancelFunc
|
|
ctxCancel <-chan struct{} // nil if no context.
|
|
ctxErr func() error
|
|
}
|
|
|
|
// WithNErrs returns a new Group with length of errs slice upto nerrs,
|
|
// upon Wait() errors are returned collected from all tasks.
|
|
func WithNErrs(nerrs int) *Group {
|
|
return &Group{errs: make([]error, nerrs), firstErr: -1}
|
|
}
|
|
|
|
// Wait blocks until all function calls from the Go method have returned, then
|
|
// returns the slice of errors from all function calls.
|
|
func (g *Group) Wait() []error {
|
|
g.wg.Wait()
|
|
if g.cancel != nil {
|
|
g.cancel()
|
|
}
|
|
return g.errs
|
|
}
|
|
|
|
// WaitErr blocks until all function calls from the Go method have returned, then
|
|
// returns the first error returned.
|
|
func (g *Group) WaitErr() error {
|
|
g.wg.Wait()
|
|
if g.cancel != nil {
|
|
g.cancel()
|
|
}
|
|
if g.firstErr >= 0 && len(g.errs) > int(g.firstErr) {
|
|
// len(g.errs) > int(g.firstErr) is for then used uninitialized.
|
|
return g.errs[g.firstErr]
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// WithConcurrency allows to limit the concurrency of the group.
|
|
// This must be called before starting any async processes.
|
|
// There is no order to which functions are allowed to run.
|
|
// If n <= 0 no concurrency limits are enforced.
|
|
// g is modified and returned as well.
|
|
func (g *Group) WithConcurrency(n int) *Group {
|
|
if n <= 0 {
|
|
g.bucket = nil
|
|
return g
|
|
}
|
|
|
|
// Fill bucket with tokens
|
|
g.bucket = make(chan struct{}, n)
|
|
for i := 0; i < n; i++ {
|
|
g.bucket <- struct{}{}
|
|
}
|
|
return g
|
|
}
|
|
|
|
// WithCancelOnError will return a context that is canceled
|
|
// as soon as an error occurs.
|
|
// The returned CancelFunc must always be called similar to context.WithCancel.
|
|
// If the supplied context is canceled any goroutines waiting for execution are also canceled.
|
|
func (g *Group) WithCancelOnError(ctx context.Context) (context.Context, context.CancelFunc) {
|
|
ctx, g.cancel = context.WithCancel(ctx)
|
|
g.ctxCancel = ctx.Done()
|
|
g.ctxErr = ctx.Err
|
|
return ctx, g.cancel
|
|
}
|
|
|
|
// Go calls the given function in a new goroutine.
|
|
//
|
|
// The errors will be collected in errs slice and returned by Wait().
|
|
func (g *Group) Go(f func() error, index int) {
|
|
g.wg.Add(1)
|
|
go func() {
|
|
defer g.wg.Done()
|
|
if g.bucket != nil {
|
|
// Wait for token
|
|
select {
|
|
case <-g.bucket:
|
|
defer func() {
|
|
// Put back token..
|
|
g.bucket <- struct{}{}
|
|
}()
|
|
case <-g.ctxCancel:
|
|
if len(g.errs) > index {
|
|
atomic.CompareAndSwapInt64(&g.firstErr, -1, int64(index))
|
|
g.errs[index] = g.ctxErr()
|
|
}
|
|
return
|
|
}
|
|
}
|
|
if err := f(); err != nil {
|
|
if len(g.errs) > index {
|
|
atomic.CompareAndSwapInt64(&g.firstErr, -1, int64(index))
|
|
g.errs[index] = err
|
|
}
|
|
if g.cancel != nil {
|
|
g.cancel()
|
|
}
|
|
}
|
|
}()
|
|
}
|