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119 lines
2.5 KiB
119 lines
2.5 KiB
package errgroup
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import (
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"context"
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"fmt"
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"runtime"
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"sync"
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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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err error
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wg sync.WaitGroup
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errOnce sync.Once
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workerOnce sync.Once
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ch chan func(ctx context.Context) error
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chs []func(ctx context.Context) error
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ctx context.Context
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cancel func()
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}
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// WithContext create a Group.
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// given function from Go will receive this context,
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func WithContext(ctx context.Context) *Group {
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return &Group{ctx: ctx}
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}
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// WithCancel create a new Group and an associated Context derived from ctx.
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//
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// given function from Go will receive context derived from this ctx,
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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 WithCancel(ctx context.Context) *Group {
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ctx, cancel := context.WithCancel(ctx)
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return &Group{ctx: ctx, cancel: cancel}
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}
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func (g *Group) do(f func(ctx context.Context) error) {
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ctx := g.ctx
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if ctx == nil {
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ctx = context.Background()
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}
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var err error
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defer func() {
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if r := recover(); r != nil {
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buf := make([]byte, 64<<10)
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buf = buf[:runtime.Stack(buf, false)]
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err = fmt.Errorf("errgroup: panic recovered: %s\n%s", r, buf)
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}
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if 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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g.wg.Done()
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}()
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err = f(ctx)
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}
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// GOMAXPROCS set max goroutine to work.
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func (g *Group) GOMAXPROCS(n int) {
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if n <= 0 {
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panic("errgroup: GOMAXPROCS must great than 0")
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}
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g.workerOnce.Do(func() {
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g.ch = make(chan func(context.Context) error, n)
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for i := 0; i < n; i++ {
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go func() {
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for f := range g.ch {
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g.do(f)
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}
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}()
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}
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})
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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(ctx context.Context) error) {
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g.wg.Add(1)
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if g.ch != nil {
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select {
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case g.ch <- f:
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default:
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g.chs = append(g.chs, f)
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}
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return
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}
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go g.do(f)
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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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if g.ch != nil {
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for _, f := range g.chs {
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g.ch <- f
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}
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}
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g.wg.Wait()
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if g.ch != nil {
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close(g.ch) // let all receiver exit
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}
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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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