68 lines
1.6 KiB
Go
68 lines
1.6 KiB
Go
// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package errgroup provides synchronization, error propagation, and Context
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// cancelation for groups of goroutines working on subtasks of a common task.
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package errgroup
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import (
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"sync"
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"golang.org/x/net/context"
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)
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// A Group is a collection of goroutines working on subtasks that are part of
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// the same overall task.
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//
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// A zero Group is valid and does not cancel on error.
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type Group struct {
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cancel func()
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wg sync.WaitGroup
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errOnce sync.Once
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err error
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}
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// WithContext returns a new Group and an associated Context derived from ctx.
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//
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// The derived Context is canceled the first time a function passed to Go
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// returns a non-nil error or the first time Wait returns, whichever occurs
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// first.
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func WithContext(ctx context.Context) (*Group, context.Context) {
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ctx, cancel := context.WithCancel(ctx)
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return &Group{cancel: cancel}, ctx
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}
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// Wait blocks until all function calls from the Go method have returned, then
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// returns the first non-nil error (if any) from them.
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func (g *Group) Wait() error {
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g.wg.Wait()
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if g.cancel != nil {
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g.cancel()
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}
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return g.err
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}
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// Go calls the given function in a new goroutine.
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//
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// The first call to return a non-nil error cancels the group; its error will be
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// returned by Wait.
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func (g *Group) Go(f func() error) {
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g.wg.Add(1)
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go func() {
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defer g.wg.Done()
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if err := f(); err != nil {
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g.errOnce.Do(func() {
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g.err = err
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if g.cancel != nil {
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g.cancel()
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}
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})
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}
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}()
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}
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