unison/multierrgroup.go

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// license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright
// ownership. Elasticsearch B.V. licenses this file to you 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 unison

import (
	"context"
	"sync"
)

// MultiErrGroup is a collection of goroutines working on subtasks
// concurrently.  The group waits until all subtasks have finished and collects
// all errors encountered.
//
// The zero value of MultiErrGroup is a valid group.
type MultiErrGroup struct {
	mu   sync.Mutex
	errs []error
	wg   sync.WaitGroup
}

// Go starts a new go-routine, collecting errors encounted into the
// MultiErrGroup.
func (g *MultiErrGroup) Go(fn func() error) {
	g.wg.Add(1)
	go func() {
		defer g.wg.Done()
		err := fn()
		if err != nil && err != context.Canceled {
			g.mu.Lock()
			defer g.mu.Unlock()
			g.errs = append(g.errs, err)
		}
	}()
}

// Wait waits until all go-routines have been stopped and returns all errors
// encountered.
func (g *MultiErrGroup) Wait() []error {
	g.wg.Wait()
	g.mu.Lock()
	defer g.mu.Unlock()
	return g.errs
}