vendor
This commit is contained in:
Mikaël Cluseau
67
vendor/golang.org/x/sync/errgroup/errgroup.go
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67
vendor/golang.org/x/sync/errgroup/errgroup.go
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// 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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101
vendor/golang.org/x/sync/errgroup/errgroup_example_md5all_test.go
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101
vendor/golang.org/x/sync/errgroup/errgroup_example_md5all_test.go
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// 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_test
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import (
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"crypto/md5"
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"fmt"
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"io/ioutil"
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"log"
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"os"
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"path/filepath"
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"golang.org/x/net/context"
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"golang.org/x/sync/errgroup"
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)
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// Pipeline demonstrates the use of a Group to implement a multi-stage
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// pipeline: a version of the MD5All function with bounded parallelism from
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// https://blog.golang.org/pipelines.
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func ExampleGroup_pipeline() {
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m, err := MD5All(context.Background(), ".")
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if err != nil {
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log.Fatal(err)
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}
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for k, sum := range m {
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fmt.Printf("%s:\t%x\n", k, sum)
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}
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}
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type result struct {
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path string
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sum [md5.Size]byte
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}
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// MD5All reads all the files in the file tree rooted at root and returns a map
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// from file path to the MD5 sum of the file's contents. If the directory walk
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// fails or any read operation fails, MD5All returns an error.
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func MD5All(ctx context.Context, root string) (map[string][md5.Size]byte, error) {
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// ctx is canceled when g.Wait() returns. When this version of MD5All returns
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// - even in case of error! - we know that all of the goroutines have finished
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// and the memory they were using can be garbage-collected.
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g, ctx := errgroup.WithContext(ctx)
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paths := make(chan string)
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g.Go(func() error {
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defer close(paths)
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return filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
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if err != nil {
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return err
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}
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if !info.Mode().IsRegular() {
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return nil
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}
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select {
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case paths <- path:
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case <-ctx.Done():
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return ctx.Err()
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}
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return nil
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})
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})
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// Start a fixed number of goroutines to read and digest files.
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c := make(chan result)
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const numDigesters = 20
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for i := 0; i < numDigesters; i++ {
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g.Go(func() error {
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for path := range paths {
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data, err := ioutil.ReadFile(path)
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if err != nil {
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return err
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}
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select {
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case c <- result{path, md5.Sum(data)}:
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case <-ctx.Done():
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return ctx.Err()
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}
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}
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return nil
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})
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}
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go func() {
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g.Wait()
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close(c)
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}()
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m := make(map[string][md5.Size]byte)
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for r := range c {
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m[r.path] = r.sum
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}
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// Check whether any of the goroutines failed. Since g is accumulating the
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// errors, we don't need to send them (or check for them) in the individual
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// results sent on the channel.
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if err := g.Wait(); err != nil {
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return nil, err
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}
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return m, nil
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}
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176
vendor/golang.org/x/sync/errgroup/errgroup_test.go
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176
vendor/golang.org/x/sync/errgroup/errgroup_test.go
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@ -0,0 +1,176 @@
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// 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_test
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import (
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"errors"
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"fmt"
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"net/http"
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"os"
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"testing"
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"golang.org/x/net/context"
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"golang.org/x/sync/errgroup"
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)
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var (
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Web = fakeSearch("web")
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Image = fakeSearch("image")
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Video = fakeSearch("video")
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)
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type Result string
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type Search func(ctx context.Context, query string) (Result, error)
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func fakeSearch(kind string) Search {
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return func(_ context.Context, query string) (Result, error) {
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return Result(fmt.Sprintf("%s result for %q", kind, query)), nil
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}
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}
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// JustErrors illustrates the use of a Group in place of a sync.WaitGroup to
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// simplify goroutine counting and error handling. This example is derived from
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// the sync.WaitGroup example at https://golang.org/pkg/sync/#example_WaitGroup.
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func ExampleGroup_justErrors() {
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var g errgroup.Group
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var urls = []string{
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"http://www.golang.org/",
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"http://www.google.com/",
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"http://www.somestupidname.com/",
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}
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for _, url := range urls {
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// Launch a goroutine to fetch the URL.
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url := url // https://golang.org/doc/faq#closures_and_goroutines
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g.Go(func() error {
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// Fetch the URL.
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resp, err := http.Get(url)
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if err == nil {
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resp.Body.Close()
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}
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return err
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})
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}
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// Wait for all HTTP fetches to complete.
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if err := g.Wait(); err == nil {
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fmt.Println("Successfully fetched all URLs.")
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}
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}
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// Parallel illustrates the use of a Group for synchronizing a simple parallel
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// task: the "Google Search 2.0" function from
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// https://talks.golang.org/2012/concurrency.slide#46, augmented with a Context
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// and error-handling.
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func ExampleGroup_parallel() {
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Google := func(ctx context.Context, query string) ([]Result, error) {
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g, ctx := errgroup.WithContext(ctx)
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searches := []Search{Web, Image, Video}
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results := make([]Result, len(searches))
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for i, search := range searches {
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i, search := i, search // https://golang.org/doc/faq#closures_and_goroutines
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g.Go(func() error {
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result, err := search(ctx, query)
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if err == nil {
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results[i] = result
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}
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return err
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})
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}
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if err := g.Wait(); err != nil {
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return nil, err
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}
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return results, nil
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}
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results, err := Google(context.Background(), "golang")
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if err != nil {
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fmt.Fprintln(os.Stderr, err)
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return
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}
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for _, result := range results {
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fmt.Println(result)
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}
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// Output:
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// web result for "golang"
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// image result for "golang"
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// video result for "golang"
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}
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func TestZeroGroup(t *testing.T) {
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err1 := errors.New("errgroup_test: 1")
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err2 := errors.New("errgroup_test: 2")
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cases := []struct {
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errs []error
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}{
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{errs: []error{}},
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{errs: []error{nil}},
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{errs: []error{err1}},
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{errs: []error{err1, nil}},
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{errs: []error{err1, nil, err2}},
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}
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for _, tc := range cases {
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var g errgroup.Group
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var firstErr error
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for i, err := range tc.errs {
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err := err
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g.Go(func() error { return err })
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if firstErr == nil && err != nil {
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firstErr = err
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}
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if gErr := g.Wait(); gErr != firstErr {
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t.Errorf("after %T.Go(func() error { return err }) for err in %v\n"+
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"g.Wait() = %v; want %v",
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g, tc.errs[:i+1], err, firstErr)
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}
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}
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}
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}
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func TestWithContext(t *testing.T) {
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errDoom := errors.New("group_test: doomed")
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cases := []struct {
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errs []error
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want error
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}{
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{want: nil},
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{errs: []error{nil}, want: nil},
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{errs: []error{errDoom}, want: errDoom},
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{errs: []error{errDoom, nil}, want: errDoom},
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}
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for _, tc := range cases {
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g, ctx := errgroup.WithContext(context.Background())
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for _, err := range tc.errs {
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err := err
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g.Go(func() error { return err })
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}
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if err := g.Wait(); err != tc.want {
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t.Errorf("after %T.Go(func() error { return err }) for err in %v\n"+
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"g.Wait() = %v; want %v",
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g, tc.errs, err, tc.want)
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}
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canceled := false
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select {
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case <-ctx.Done():
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canceled = true
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default:
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}
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if !canceled {
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t.Errorf("after %T.Go(func() error { return err }) for err in %v\n"+
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"ctx.Done() was not closed",
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g, tc.errs)
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}
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}
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}
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