parallelizer.go

Documentation: k8s.io/client-go/util/workqueue

     1  /*
     2  Copyright 2016 The Kubernetes Authors.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8      http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package workqueue
    18  
    19  import (
    20  	"context"
    21  	"sync"
    22  
    23  	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
    24  )
    25  
    26  type DoWorkPieceFunc func(piece int)
    27  
    28  type options struct {
    29  	chunkSize int
    30  }
    31  
    32  type Options func(*options)
    33  
    34  // WithChunkSize allows to set chunks of work items to the workers, rather than
    35  // processing one by one.
    36  // It is recommended to use this option if the number of pieces significantly
    37  // higher than the number of workers and the work done for each item is small.
    38  func WithChunkSize(c int) func(*options) {
    39  	return func(o *options) {
    40  		o.chunkSize = c
    41  	}
    42  }
    43  
    44  // ParallelizeUntil is a framework that allows for parallelizing N
    45  // independent pieces of work until done or the context is canceled.
    46  func ParallelizeUntil(ctx context.Context, workers, pieces int, doWorkPiece DoWorkPieceFunc, opts ...Options) {
    47  	if pieces == 0 {
    48  		return
    49  	}
    50  	o := options{}
    51  	for _, opt := range opts {
    52  		opt(&o)
    53  	}
    54  	chunkSize := o.chunkSize
    55  	if chunkSize < 1 {
    56  		chunkSize = 1
    57  	}
    58  
    59  	chunks := ceilDiv(pieces, chunkSize)
    60  	toProcess := make(chan int, chunks)
    61  	for i := 0; i < chunks; i++ {
    62  		toProcess <- i
    63  	}
    64  	close(toProcess)
    65  
    66  	var stop <-chan struct{}
    67  	if ctx != nil {
    68  		stop = ctx.Done()
    69  	}
    70  	if chunks < workers {
    71  		workers = chunks
    72  	}
    73  	wg := sync.WaitGroup{}
    74  	wg.Add(workers)
    75  	for i := 0; i < workers; i++ {
    76  		go func() {
    77  			defer utilruntime.HandleCrash()
    78  			defer wg.Done()
    79  			for chunk := range toProcess {
    80  				start := chunk * chunkSize
    81  				end := start + chunkSize
    82  				if end > pieces {
    83  					end = pieces
    84  				}
    85  				for p := start; p < end; p++ {
    86  					select {
    87  					case <-stop:
    88  						return
    89  					default:
    90  						doWorkPiece(p)
    91  					}
    92  				}
    93  			}
    94  		}()
    95  	}
    96  	wg.Wait()
    97  }
    98  
    99  func ceilDiv(a, b int) int {
   100  	return (a + b - 1) / b
   101  }
   102
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