github.com/m3db/m3@v1.5.0/src/x/sync/example_test.go (about)

     1  // Copyright (c) 2017 Uber Technologies, Inc.
     2  //
     3  // Permission is hereby granted, free of charge, to any person obtaining a copy
     4  // of this software and associated documentation files (the "Software"), to deal
     5  // in the Software without restriction, including without limitation the rights
     6  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     7  // copies of the Software, and to permit persons to whom the Software is
     8  // furnished to do so, subject to the following conditions:
     9  //
    10  // The above copyright notice and this permission notice shall be included in
    11  // all copies or substantial portions of the Software.
    12  //
    13  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    14  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    15  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    16  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    17  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    18  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    19  // THE SOFTWARE.
    20  
    21  package sync_test
    22  
    23  import (
    24  	"fmt"
    25  	"log"
    26  	"sync"
    27  
    28  	xsync "github.com/m3db/m3/src/x/sync"
    29  )
    30  
    31  type response struct {
    32  	a int
    33  }
    34  
    35  func ExampleWorkerPool() {
    36  	var (
    37  		wg          sync.WaitGroup
    38  		workers     = xsync.NewWorkerPool(3)
    39  		errorCh     = make(chan error, 1)
    40  		numRequests = 9
    41  		responses   = make([]response, numRequests)
    42  	)
    43  
    44  	wg.Add(numRequests)
    45  	workers.Init()
    46  
    47  	for i := 0; i < numRequests; i++ {
    48  		// Capture loop variable.
    49  		i := i
    50  
    51  		// Execute request on worker pool.
    52  		workers.Go(func() {
    53  			defer wg.Done()
    54  
    55  			var err error
    56  
    57  			// Perform some work which may fail.
    58  			resp := response{a: i}
    59  
    60  			if err != nil {
    61  				// Return the first error that is encountered.
    62  				select {
    63  				case errorCh <- err:
    64  				default:
    65  				}
    66  
    67  				return
    68  			}
    69  
    70  			// Can concurrently modify responses since each iteration updates a
    71  			// different index.
    72  			responses[i] = resp
    73  		})
    74  	}
    75  
    76  	// Wait for all requests to finish.
    77  	wg.Wait()
    78  
    79  	close(errorCh)
    80  	if err := <-errorCh; err != nil {
    81  		log.Fatal(err)
    82  	}
    83  
    84  	var total int
    85  	for _, r := range responses {
    86  		total += r.a
    87  	}
    88  
    89  	fmt.Printf("Total is %v", total)
    90  	// Output: Total is 36
    91  }