|
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176 |
- // Copyright 2016 The Go Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style
- // license that can be found in the LICENSE file.
-
- package errgroup_test
-
- import (
- "context"
- "errors"
- "fmt"
- "net/http"
- "os"
- "testing"
-
- "golang.org/x/sync/errgroup"
- )
-
- var (
- Web = fakeSearch("web")
- Image = fakeSearch("image")
- Video = fakeSearch("video")
- )
-
- type Result string
- type Search func(ctx context.Context, query string) (Result, error)
-
- func fakeSearch(kind string) Search {
- return func(_ context.Context, query string) (Result, error) {
- return Result(fmt.Sprintf("%s result for %q", kind, query)), nil
- }
- }
-
- // JustErrors illustrates the use of a Group in place of a sync.WaitGroup to
- // simplify goroutine counting and error handling. This example is derived from
- // the sync.WaitGroup example at https://golang.org/pkg/sync/#example_WaitGroup.
- func ExampleGroup_justErrors() {
- var g errgroup.Group
- var urls = []string{
- "http://www.golang.org/",
- "http://www.google.com/",
- "http://www.somestupidname.com/",
- }
- for _, url := range urls {
- // Launch a goroutine to fetch the URL.
- url := url // https://golang.org/doc/faq#closures_and_goroutines
- g.Go(func() error {
- // Fetch the URL.
- resp, err := http.Get(url)
- if err == nil {
- resp.Body.Close()
- }
- return err
- })
- }
- // Wait for all HTTP fetches to complete.
- if err := g.Wait(); err == nil {
- fmt.Println("Successfully fetched all URLs.")
- }
- }
-
- // Parallel illustrates the use of a Group for synchronizing a simple parallel
- // task: the "Google Search 2.0" function from
- // https://talks.golang.org/2012/concurrency.slide#46, augmented with a Context
- // and error-handling.
- func ExampleGroup_parallel() {
- Google := func(ctx context.Context, query string) ([]Result, error) {
- g, ctx := errgroup.WithContext(ctx)
-
- searches := []Search{Web, Image, Video}
- results := make([]Result, len(searches))
- for i, search := range searches {
- i, search := i, search // https://golang.org/doc/faq#closures_and_goroutines
- g.Go(func() error {
- result, err := search(ctx, query)
- if err == nil {
- results[i] = result
- }
- return err
- })
- }
- if err := g.Wait(); err != nil {
- return nil, err
- }
- return results, nil
- }
-
- results, err := Google(context.Background(), "golang")
- if err != nil {
- fmt.Fprintln(os.Stderr, err)
- return
- }
- for _, result := range results {
- fmt.Println(result)
- }
-
- // Output:
- // web result for "golang"
- // image result for "golang"
- // video result for "golang"
- }
-
- func TestZeroGroup(t *testing.T) {
- err1 := errors.New("errgroup_test: 1")
- err2 := errors.New("errgroup_test: 2")
-
- cases := []struct {
- errs []error
- }{
- {errs: []error{}},
- {errs: []error{nil}},
- {errs: []error{err1}},
- {errs: []error{err1, nil}},
- {errs: []error{err1, nil, err2}},
- }
-
- for _, tc := range cases {
- var g errgroup.Group
-
- var firstErr error
- for i, err := range tc.errs {
- err := err
- g.Go(func() error { return err })
-
- if firstErr == nil && err != nil {
- firstErr = err
- }
-
- if gErr := g.Wait(); gErr != firstErr {
- t.Errorf("after %T.Go(func() error { return err }) for err in %v\n"+
- "g.Wait() = %v; want %v",
- g, tc.errs[:i+1], err, firstErr)
- }
- }
- }
- }
-
- func TestWithContext(t *testing.T) {
- errDoom := errors.New("group_test: doomed")
-
- cases := []struct {
- errs []error
- want error
- }{
- {want: nil},
- {errs: []error{nil}, want: nil},
- {errs: []error{errDoom}, want: errDoom},
- {errs: []error{errDoom, nil}, want: errDoom},
- }
-
- for _, tc := range cases {
- g, ctx := errgroup.WithContext(context.Background())
-
- for _, err := range tc.errs {
- err := err
- g.Go(func() error { return err })
- }
-
- if err := g.Wait(); err != tc.want {
- t.Errorf("after %T.Go(func() error { return err }) for err in %v\n"+
- "g.Wait() = %v; want %v",
- g, tc.errs, err, tc.want)
- }
-
- canceled := false
- select {
- case <-ctx.Done():
- canceled = true
- default:
- }
- if !canceled {
- t.Errorf("after %T.Go(func() error { return err }) for err in %v\n"+
- "ctx.Done() was not closed",
- g, tc.errs)
- }
- }
- }
|