What is channel buffer size?

user_407248 0
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I'm trying to create an asynchronous channel and I've been looking at http://golang.org/ref/spec#Making_slices_maps_and_channels. 

c := make(chan int, 10)         // channel with a buffer size of 10

What does it mean that the buffer size is 10? What specifically does the buffer size represent/limit?

go channel
3 Answers

The following code illustrates the blocking of unbuffered channel:

// to see the diff, change 0 to 1
c := make(chan struct{}, 0)
go func() {
    time.Sleep(2 * time.Second)
    <-c
}()
start := time.Now()
c <- struct{}{} // block, if channel size is 0
elapsed := time.Since(start)
fmt.Printf("Elapsed: %v\n", elapsed)

You may play with the code here.

user_13518450 
package main

import (
    "fmt"
    "time"
)

func receiver(ch <-chan int) {
    time.Sleep(500 * time.Millisecond)
    msg := <-ch
    fmt.Printf("receive messages  %d from the channel\n", msg)
}

func main() {
    start := time.Now()
    zero_buffer_ch := make(chan int, 0)
    go receiver(zero_buffer_ch)
    zero_buffer_ch <- 444
    elapsed := time.Since(start)    
    fmt.Printf("Elapsed using zero_buffer channel: %v\n", elapsed)

    restart := time.Now()
    non_zero_buffer_ch := make(chan int, 1)
    go receiver(non_zero_buffer_ch)
    non_zero_buffer_ch <- 4444
    reelapsed := time.Since(restart)
    fmt.Printf("Elapsed using non zero_buffer channel: %v\n", reelapsed)
}

result:

receive messages 444 from the channel

Elapsed using zero_buffer channel: 505.6729ms

Elapsed using non zero_buffer channel: 0s

user_24809720
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