revert "improve plugins discovery performance"

This reverts commit 62f2358b99.

Spawning a goroutine for each iteration in the loop when listing
plugins is racy unfortunately. `plugins` slice is protected with
a mutex so not sure why it fails.

I tried using a channel to collect the plugins instead of a slice
to guarantee that they will be appended to the list in the order
they are processed but no dice.

I also tried without errgroup package and simply use sync.WaitGroup
but same. I have also created an extra channel to receive errors
from the goroutines but racy too.

I think the change in this function is not related to the race
condition but newPlugin is. So revert in the meantime :(

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

cli-plugins/manager/manager.go

@@ -1,18 +1,15 @@
 package manager
 
 import (
-	"context"
 	"os"
 	"path/filepath"
 	"sort"
 	"strings"
-	"sync"
 
 	"github.com/docker/cli/cli/command"
 	"github.com/docker/cli/cli/config"
 	"github.com/fvbommel/sortorder"
 	"github.com/spf13/cobra"
-	"golang.org/x/sync/errgroup"
 	exec "golang.org/x/sys/execabs"
 )
 
@@ -149,31 +146,19 @@ func ListPlugins(dockerCli command.Cli, rootcmd *cobra.Command) ([]Plugin, error
 	}
 
 	var plugins []Plugin
-	var mu sync.Mutex
-	eg, _ := errgroup.WithContext(context.TODO())
 	for _, paths := range candidates {
-		func(paths []string) {
-			eg.Go(func() error {
 		if len(paths) == 0 {
-					return nil
+			continue
 		}
 		c := &candidate{paths[0]}
 		p, err := newPlugin(c, rootcmd)
 		if err != nil {
-					return err
+			return nil, err
 		}
 		if !IsNotFound(p.Err) {
 			p.ShadowedPaths = paths[1:]
-					mu.Lock()
-					defer mu.Unlock()
 			plugins = append(plugins, p)
 		}
-				return nil
-			})
-		}(paths)
-	}
-	if err := eg.Wait(); err != nil {
-		return nil, err
 	}
 
 	sort.Slice(plugins, func(i, j int) bool {

vendor.mod

@@ -49,7 +49,6 @@ require (
 	github.com/theupdateframework/notary v0.7.1-0.20210315103452-bf96a202a09a
 	github.com/tonistiigi/go-rosetta v0.0.0-20200727161949-f79598599c5d
 	github.com/xeipuuv/gojsonschema v1.2.0
-	golang.org/x/sync v0.1.0
 	golang.org/x/sys v0.6.0
 	golang.org/x/term v0.5.0
 	golang.org/x/text v0.7.0

vendor.sum

@@ -524,8 +524,6 @@ golang.org/x/sync v0.0.0-20200317015054-43a5402ce75a/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sync v0.0.0-20200625203802-6e8e738ad208/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20201207232520-09787c993a3a/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.1.0 h1:wsuoTGHzEhffawBOhz5CYhcrV4IdKZbEyZjBMuTp12o=
-golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180905080454-ebe1bf3edb33/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180909124046-d0be0721c37e/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=

vendor/golang.org/x/sync/LICENSE

@@ -1,27 +0,0 @@
-Copyright (c) 2009 The Go Authors. All rights reserved.
-
-Redistribution and use in source and binary forms, with or without
-modification, are permitted provided that the following conditions are
-met:
-
-   * Redistributions of source code must retain the above copyright
-notice, this list of conditions and the following disclaimer.
-   * Redistributions in binary form must reproduce the above
-copyright notice, this list of conditions and the following disclaimer
-in the documentation and/or other materials provided with the
-distribution.
-   * Neither the name of Google Inc. nor the names of its
-contributors may be used to endorse or promote products derived from
-this software without specific prior written permission.
-
-THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

vendor/golang.org/x/sync/PATENTS

@@ -1,22 +0,0 @@
-Additional IP Rights Grant (Patents)
-
-"This implementation" means the copyrightable works distributed by
-Google as part of the Go project.
-
-Google hereby grants to You a perpetual, worldwide, non-exclusive,
-no-charge, royalty-free, irrevocable (except as stated in this section)
-patent license to make, have made, use, offer to sell, sell, import,
-transfer and otherwise run, modify and propagate the contents of this
-implementation of Go, where such license applies only to those patent
-claims, both currently owned or controlled by Google and acquired in
-the future, licensable by Google that are necessarily infringed by this
-implementation of Go.  This grant does not include claims that would be
-infringed only as a consequence of further modification of this
-implementation.  If you or your agent or exclusive licensee institute or
-order or agree to the institution of patent litigation against any
-entity (including a cross-claim or counterclaim in a lawsuit) alleging
-that this implementation of Go or any code incorporated within this
-implementation of Go constitutes direct or contributory patent
-infringement, or inducement of patent infringement, then any patent
-rights granted to you under this License for this implementation of Go
-shall terminate as of the date such litigation is filed.

vendor/golang.org/x/sync/errgroup/errgroup.go

@@ -1,132 +0,0 @@
-// 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 provides synchronization, error propagation, and Context
-// cancelation for groups of goroutines working on subtasks of a common task.
-package errgroup
-
-import (
-	"context"
-	"fmt"
-	"sync"
-)
-
-type token struct{}
-
-// A Group is a collection of goroutines working on subtasks that are part of
-// the same overall task.
-//
-// A zero Group is valid, has no limit on the number of active goroutines,
-// and does not cancel on error.
-type Group struct {
-	cancel func()
-
-	wg sync.WaitGroup
-
-	sem chan token
-
-	errOnce sync.Once
-	err     error
-}
-
-func (g *Group) done() {
-	if g.sem != nil {
-		<-g.sem
-	}
-	g.wg.Done()
-}
-
-// WithContext returns a new Group and an associated Context derived from ctx.
-//
-// The derived Context is canceled the first time a function passed to Go
-// returns a non-nil error or the first time Wait returns, whichever occurs
-// first.
-func WithContext(ctx context.Context) (*Group, context.Context) {
-	ctx, cancel := context.WithCancel(ctx)
-	return &Group{cancel: cancel}, ctx
-}
-
-// Wait blocks until all function calls from the Go method have returned, then
-// returns the first non-nil error (if any) from them.
-func (g *Group) Wait() error {
-	g.wg.Wait()
-	if g.cancel != nil {
-		g.cancel()
-	}
-	return g.err
-}
-
-// Go calls the given function in a new goroutine.
-// It blocks until the new goroutine can be added without the number of
-// active goroutines in the group exceeding the configured limit.
-//
-// The first call to return a non-nil error cancels the group's context, if the
-// group was created by calling WithContext. The error will be returned by Wait.
-func (g *Group) Go(f func() error) {
-	if g.sem != nil {
-		g.sem <- token{}
-	}
-
-	g.wg.Add(1)
-	go func() {
-		defer g.done()
-
-		if err := f(); err != nil {
-			g.errOnce.Do(func() {
-				g.err = err
-				if g.cancel != nil {
-					g.cancel()
-				}
-			})
-		}
-	}()
-}
-
-// TryGo calls the given function in a new goroutine only if the number of
-// active goroutines in the group is currently below the configured limit.
-//
-// The return value reports whether the goroutine was started.
-func (g *Group) TryGo(f func() error) bool {
-	if g.sem != nil {
-		select {
-		case g.sem <- token{}:
-			// Note: this allows barging iff channels in general allow barging.
-		default:
-			return false
-		}
-	}
-
-	g.wg.Add(1)
-	go func() {
-		defer g.done()
-
-		if err := f(); err != nil {
-			g.errOnce.Do(func() {
-				g.err = err
-				if g.cancel != nil {
-					g.cancel()
-				}
-			})
-		}
-	}()
-	return true
-}
-
-// SetLimit limits the number of active goroutines in this group to at most n.
-// A negative value indicates no limit.
-//
-// Any subsequent call to the Go method will block until it can add an active
-// goroutine without exceeding the configured limit.
-//
-// The limit must not be modified while any goroutines in the group are active.
-func (g *Group) SetLimit(n int) {
-	if n < 0 {
-		g.sem = nil
-		return
-	}
-	if len(g.sem) != 0 {
-		panic(fmt.Errorf("errgroup: modify limit while %v goroutines in the group are still active", len(g.sem)))
-	}
-	g.sem = make(chan token, n)
-}

vendor/modules.txt

@@ -278,9 +278,6 @@ golang.org/x/net/internal/socks
 golang.org/x/net/internal/timeseries
 golang.org/x/net/proxy
 golang.org/x/net/trace
-# golang.org/x/sync v0.1.0
-## explicit
-golang.org/x/sync/errgroup
 # golang.org/x/sys v0.6.0
 ## explicit; go 1.17
 golang.org/x/sys/execabs