Add new throttler pkg forked from nozzle/throttler

throttler/README.md

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+# Throttler - Intelligent WaitGroups
+
+[![GoDoc](https://pkg.go.dev/sigs.k8s.io/release-utils/throttler?status.svg)](https://pkg.go.dev/sigs.k8s.io/release-utils/throttler?status.svg)
+
+__Note:__ This package was adopted by the Kubernetes RelEng team to continue its
+maintenance, it was forked from github.com/nozzle/throttle at 
+[2ea9822](https://github.com/nozzle/throttler/commit/2ea982251481626167b7f83be1434b5c42540c1a).
+
+Throttler fills the gap between sync.WaitGroup and manually monitoring your 
+goroutines with channels. The API is almost identical to Wait Groups, but it 
+allows you to set a max number of workers that can be running simultaneously. 
+It uses channels internally to block until a job completes by calling Done() or 
+until all jobs have been completed. It also provides a built in error channel 
+that captures your goroutine errors and provides access to them as `[]error` 
+after you exit the loop.
+
+See a fully functional example of the original module on the playground at http://bit.ly/throttler-v3
+
+Compare the Throttler example to the sync.WaitGroup example from http://golang.org/pkg/sync/#example_WaitGroup
+
+### How to use Throttler
+
+```golang
+// This example fetches several URLs concurrently,
+// using a Throttler to block until all the fetches are complete.
+// Compare to http://golang.org/pkg/sync/#example_WaitGroup
+func ExampleThrottler() {
+	var urls = []string{
+		"http://www.golang.org/",
+		"http://www.google.com/",
+		"http://www.somestupidname.com/",
+	}
+	// Create a new Throttler that will get 2 urls at a time
+	t := throttler.New(2, len(urls))
+	for _, url := range urls {
+		// Launch a goroutine to fetch the URL.
+		go func(url string) {
+			// Fetch the URL.
+			err := http.Get(url)
+			// Let Throttler know when the goroutine completes
+			// so it can dispatch another worker
+			t.Done(err)
+		}(url)
+		// Pauses until a worker is available or all jobs have been completed
+		// Returning the total number of goroutines that have errored
+		// lets you choose to break out of the loop without starting any more
+		errorCount := t.Throttle()
+	}
+}
+```
+
+### vs How to use a sync.WaitGroup
+
+```golang
+// This example fetches several URLs concurrently,
+// using a WaitGroup to block until all the fetches are complete.
+func ExampleWaitGroup() {
+	var wg sync.WaitGroup
+	var urls = []string{
+		"http://www.golang.org/",
+		"http://www.google.com/",
+		"http://www.somestupidname.com/",
+	}
+	for _, url := range urls {
+		// Increment the WaitGroup counter.
+		wg.Add(1)
+		// Launch a goroutine to fetch the URL.
+		go func(url string) {
+			// Decrement the counter when the goroutine completes.
+			defer wg.Done()
+			// Fetch the URL.
+			http.Get(url)
+		}(url)
+	}
+	// Wait for all HTTP fetches to complete.
+	wg.Wait()
+}
+```

throttler/example_test.go

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+/*
+Copyright 2024 The Kubernetes Authors.
+
+Licensed 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.
+*/
+
+// This package was forked and adapted from the original at
+// pkg:golang/github.com/nozzle/throttler@2ea982251481626167b7f83be1434b5c42540c1a
+// full commit history has been preserved.
+
+package throttler
+
+import (
+	"fmt"
+	"os"
+)
+
+type httpPkg struct{}
+
+func (httpPkg) Get(_ string) error { return nil }
+
+var http httpPkg
+
+// This example fetches several URLs concurrently,
+// using a WaitGroup to block until all the fetches are complete.
+//
+//nolint:testableexamples // TODO - Rewrite examples
+func ExampleWaitGroup() {
+}
+
+// This example fetches several URLs concurrently,
+// using a Throttler to block until all the fetches are complete.
+// Compare to http://golang.org/pkg/sync/#example_WaitGroup
+//
+//nolint:testableexamples // TODO - Rewrite examples
+func ExampleThrottler() {
+	urls := []string{
+		"http://www.golang.org/",
+		"http://www.google.com/",
+		"http://www.somestupidname.com/",
+	}
+	// Create a new Throttler that will get 2 urls at a time
+	t := New(2, len(urls))
+	for _, url := range urls {
+		// Launch a goroutine to fetch the URL.
+		go func(url string) {
+			// Fetch the URL.
+			err := http.Get(url)
+			// Let Throttler know when the goroutine completes
+			// so it can dispatch another worker
+			t.Done(err)
+		}(url)
+		// Pauses until a worker is available or all jobs have been completed
+		// Returning the total number of goroutines that have errored
+		// lets you choose to break out of the loop without starting any more
+		errorCount := t.Throttle()
+		if errorCount > 0 {
+			break
+		}
+	}
+}
+
+// This example fetches several URLs concurrently,
+// using a Throttler to block until all the fetches are complete
+// and checks the errors returned.
+// Compare to http://golang.org/pkg/sync/#example_WaitGroup
+//
+//nolint:testableexamples // TODO - Rewrite examples
+func ExampleThrottler_errors() {
+	urls := []string{
+		"http://www.golang.org/",
+		"http://www.google.com/",
+		"http://www.somestupidname.com/",
+	}
+	// Create a new Throttler that will get 2 urls at a time
+	t := New(2, len(urls))
+	for _, url := range urls {
+		// Launch a goroutine to fetch the URL.
+		go func(url string) {
+			// Let Throttler know when the goroutine completes
+			// so it can dispatch another worker
+			defer t.Done(nil)
+			// Fetch the URL.
+			if err := http.Get(url); err != nil {
+				fmt.Fprintf(os.Stderr, "error fetching %q: %v", url, err)
+			}
+		}(url)
+		// Pauses until a worker is available or all jobs have been completed
+		t.Throttle()
+	}
+
+	if t.Err() != nil {
+		// Loop through the errors to see the details
+		for i, err := range t.Errs() {
+			fmt.Printf("error #%d: %s", i, err)
+		}
+	}
+}

throttler/throttler.go

@@ -0,0 +1,190 @@
+/*
+Copyright 2024 The Kubernetes Authors.
+
+Licensed 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.
+*/
+
+// This package was forked and adapted from the original at
+// pkg:golang/github.com/nozzle/throttler@2ea982251481626167b7f83be1434b5c42540c1a
+// full commit history has been preserved.
+
+// Package throttler fills the gap between sync.WaitGroup and manually monitoring your goroutines
+// with channels. The API is almost identical to Wait Groups, but it allows you to set
+// a max number of workers that can be running simultaneously. It uses channels internally
+// to block until a job completes by calling Done(err) or until all jobs have been completed.
+//
+// After exiting the loop where you are using Throttler, you can call the `Err` or `Errs` method to check
+// for errors. `Err` will return a single error representative of all the errors Throttler caught. The
+// `Errs` method will return all the errors as a slice of errors (`[]error`).
+//
+// Compare the Throttler example to the sync.WaitGroup example http://golang.org/pkg/sync/#example_WaitGroup
+//
+// This package was forked and adapted from the original at
+// pkg:golang/github.com/nozzle/throttler@2ea982251481626167b7f83be1434b5c42540c1a
+// full commit history has been preserved.
+//
+// See a fully functional example of the original package on the playground at http://bit.ly/throttler-v3
+package throttler
+
+import (
+	"fmt"
+	"math"
+	"sync"
+	"sync/atomic"
+)
+
+// Throttler stores all the information about the number of workers, the active
+// workers and error information.
+type Throttler struct {
+	maxWorkers    int32
+	workerCount   int32
+	batchingTotal int32
+	batchSize     int32
+	totalJobs     int32
+	jobsStarted   int32
+	jobsCompleted int32
+	doneChan      chan struct{}
+	errsMutex     *sync.Mutex
+	errs          []error
+	errorCount    int32
+}
+
+// New returns a Throttler that will govern the max number of workers and will
+// work with the total number of jobs. It panics if maxWorkers < 1.
+func New(maxWorkers, totalJobs int) *Throttler {
+	if maxWorkers < 1 {
+		panic("maxWorkers has to be at least 1")
+	}
+	return &Throttler{
+		maxWorkers: int32(maxWorkers),
+		batchSize:  1,
+		totalJobs:  int32(totalJobs),
+		doneChan:   make(chan struct{}, totalJobs),
+		errsMutex:  &sync.Mutex{},
+	}
+}
+
+// NewBatchedThrottler returns a Throttler (just like New), but also enables batching.
+func NewBatchedThrottler(maxWorkers, batchingTotal, batchSize int) *Throttler {
+	totalJobs := int(math.Ceil(float64(batchingTotal) / float64(batchSize)))
+	t := New(maxWorkers, totalJobs)
+	t.batchSize = int32(batchSize)
+	t.batchingTotal = int32(batchingTotal)
+	return t
+}
+
+// SetMaxWorkers lets you change the total number of workers that can run concurrently. NOTE: If
+// all workers are currently running, this setting is not guaranteed to take effect until one of them
+// completes and Throttle() is called again.
+func (t *Throttler) SetMaxWorkers(maxWorkers int) {
+	if maxWorkers < 1 {
+		panic("maxWorkers has to be at least 1")
+	}
+	atomic.StoreInt32(&t.maxWorkers, int32(maxWorkers))
+}
+
+// Throttle works similarly to sync.WaitGroup, except inside your goroutine dispatch
+// loop rather than after. It will not block until the number of active workers
+// matches the max number of workers designated in the call to NewThrottler or
+// all of the jobs have been dispatched. It stops blocking when Done has been called
+// as many times as totalJobs.
+func (t *Throttler) Throttle() int {
+	if atomic.LoadInt32(&t.totalJobs) < 1 {
+		return int(atomic.LoadInt32(&t.errorCount))
+	}
+	atomic.AddInt32(&t.jobsStarted, 1)
+	atomic.AddInt32(&t.workerCount, 1)
+
+	// check to see if the current number of workers equals the max number of workers
+	// if they are equal, wait for one to finish before continuing.
+	if atomic.LoadInt32(&t.workerCount) == atomic.LoadInt32(&t.maxWorkers) {
+		atomic.AddInt32(&t.jobsCompleted, 1)
+		atomic.AddInt32(&t.workerCount, -1)
+		<-t.doneChan
+	}
+
+	// check to see if all of the jobs have been started, and if so, wait until all
+	// jobs have been completed before continuing.
+	if atomic.LoadInt32(&t.jobsStarted) == atomic.LoadInt32(&t.totalJobs) {
+		for atomic.LoadInt32(&t.jobsCompleted) < atomic.LoadInt32(&t.totalJobs) {
+			atomic.AddInt32(&t.jobsCompleted, 1)
+			<-t.doneChan
+		}
+	}
+
+	return int(atomic.LoadInt32(&t.errorCount))
+}
+
+// Done lets Throttler know that a job has been completed so that another worker
+// can be activated. If Done is called less times than totalJobs,
+// Throttle will block forever.
+func (t *Throttler) Done(err error) {
+	if err != nil {
+		t.errsMutex.Lock()
+		t.errs = append(t.errs, err)
+		atomic.AddInt32(&t.errorCount, 1)
+		t.errsMutex.Unlock()
+	}
+	t.doneChan <- struct{}{}
+}
+
+// Err returns an error representative of all errors caught by throttler.
+func (t *Throttler) Err() error {
+	t.errsMutex.Lock()
+	defer t.errsMutex.Unlock()
+	if atomic.LoadInt32(&t.errorCount) == 0 {
+		return nil
+	}
+	return multiErrors(t.errs)
+}
+
+// Errs returns a slice of any errors that were received from calling Done().
+func (t *Throttler) Errs() []error {
+	t.errsMutex.Lock()
+	defer t.errsMutex.Unlock()
+	return t.errs
+}
+
+type multiErrors []error
+
+func (te multiErrors) Error() string {
+	errString := te[0].Error()
+	if len(te) > 1 {
+		errString += fmt.Sprintf(" (and %d more errors)", len(te)-1)
+	}
+	return errString
+}
+
+// BatchStartIndex returns the starting index for the next batch. The job count isn't modified
+// until th.Throttle() is called, so if you don't call Throttle before executing this
+// again, it will return the same index as before.
+func (t *Throttler) BatchStartIndex() int {
+	return int(atomic.LoadInt32(&t.jobsStarted) * atomic.LoadInt32(&t.batchSize))
+}
+
+// BatchEndIndex returns the ending index for the next batch. It either returns the full batch size
+// or the remaining amount of jobs. The job count isn't modified
+// until th.Throttle() is called, so if you don't call Throttle before executing this
+// again, it will return the same index as before.
+func (t *Throttler) BatchEndIndex() int {
+	end := (atomic.LoadInt32(&t.jobsStarted) + 1) * atomic.LoadInt32(&t.batchSize)
+	if end > atomic.LoadInt32(&t.batchingTotal) {
+		end = atomic.LoadInt32(&t.batchingTotal)
+	}
+	return int(end)
+}
+
+// TotalJobs returns the total number of jobs throttler is performing.
+func (t *Throttler) TotalJobs() int {
+	return int(atomic.LoadInt32(&t.totalJobs))
+}