为什么当我在Go中添加另一个阻塞线程时，信号处理程序不起作用？

huangapple
go评论152阅读模式
英文:

Why signal handler not work when I added another blocking thread in go?

问题

我正在尝试构建一个非常简单的TCP服务器/客户端，并且希望程序在通过Ctrl-C中断时能够关闭连接。

如果在主线程中只发送消息或只接收消息，一切都正常工作。

这是客户端的代码：

  1. package main
  3. import (
  4. 	"fmt"
  5. 	"os"
  6. 	"os/signal"
  7. 	"syscall"
  8. 	"net"
  9. 	"bufio"
  10. 	"io"
  11. 	"time"
  12. )
  14. const (
  15. 	TIMEOUT = 10
  16. )
  18. func main() {
  19. 	if len(os.Args) < 2 {
  20. 		fmt.Println(usage(os.Args[0]))
  21. 		return
  22. 	}
  23. 	
  24. 	var timeout time.Duration
  25. 	if len(os.Args) > 2 {
  26. 		timeout, _ = time.ParseDuration(os.Args[2])
  27. 	}
  28. 	if timeout == 0 {
  29. 		timeout = time.Duration(TIMEOUT * time.Second)
  30. 	}
  32. 	conn, err := net.DialTimeout("tcp", os.Args[1], timeout)
  33. 	
  34. 	if err != nil {
  35. 		fmt.Println("Error connecting: ", err.Error())
  36. 		return
  37. 	}
  39. 	defer conn.Close()
  40. 	
  41. 	c := make(chan os.Signal, 1)
  42. 	signal.Notify(c, syscall.SIGINT, syscall.SIGTERM)
  43. 	
  44. 	go func() {
  45. 		fmt.Println("wait ctrl-c")
  46. 		for _ = range c {
  47. 			fmt.Println("close on ctrl-c")
  48. 			conn.Close()
  49. 		}
  50. 	}()
  51. 	
  52. 	for {
  53. 		message, err := bufio.NewReader(os.Stdin).ReadString('\n')
  54. 		if err == io.EOF {
  55. 			fmt.Fprint(conn, message)
  56. 			break
  57. 		} else if err != nil {
  58. 			fmt.Println("Error reading: ", err.Error())
  59. 			break
  60. 		} else {
  61. 			fmt.Fprintf(conn, message)
  62. 		}
  63. 	}
  64. }
  66. func usage(filename string) string {
  67. 	return fmt.Sprintf("Usage: %s <address (ex. localhost:8016, google.com:http, [2001:db8::1]:http, etc.)> [timeout (ex. 10s, 300ms, etc.)]", filename)
  68. }

但是，当我添加了打印接收到的消息并在另一个线程中运行时，Ctrl-C处理程序不起作用。

这是代码：

  1. package main
  3. import (
  4. 	"fmt"
  5. 	"os"
  6. 	"os/signal"
  7. 	"syscall"
  8. 	"net"
  9. 	"bufio"
  10. 	"io"
  11. 	"time"
  12. )
  14. const (
  15. 	TIMEOUT = 10
  16. )
  18. func main() {
  19. 	if len(os.Args) < 2 {
  20. 		fmt.Println(usage(os.Args[0]))
  21. 		return
  22. 	}
  23. 	
  24. 	var timeout time.Duration
  25. 	if len(os.Args) > 2 {
  26. 		timeout, _ = time.ParseDuration(os.Args[2])
  27. 	}
  28. 	if timeout == 0 {
  29. 		timeout = time.Duration(TIMEOUT * time.Second)
  30. 	}
  32. 	conn, err := net.DialTimeout("tcp", os.Args[1], timeout)
  33. 	
  34. 	if err != nil {
  35. 		fmt.Println("Error connecting: ", err.Error())
  36. 		return
  37. 	}
  39. 	defer conn.Close()
  40. 	
  41. 	c := make(chan os.Signal, 1)
  42. 	signal.Notify(c, syscall.SIGINT, syscall.SIGTERM)
  43. 	
  44. 	go func() {
  45. 		fmt.Println("wait ctrl-c")
  46. 		for _ = range c {
  47. 			fmt.Println("close on ctrl-c")
  48. 			conn.Close()
  49. 		}
  50. 	}()
  51. 	// code added.
  52. 	go func() {
  53. 		for {
  54. 			message, err := bufio.NewReader(conn).ReadString('\n')
  55. 			if err == io.EOF {
  56. 				fmt.Print(message)
  57. 				break
  58. 			} else if err != nil {
  59. 				fmt.Println("Error remote reading: ", err.Error())
  60. 				break
  61. 			} else {
  62. 				fmt.Print(message)
  63. 			}
  64. 		}
  65. 		
  66. 		conn.Close()
  67. 		
  68. 		os.Exit(0)
  69. 	}()
  70. 	
  71. 	for {
  72. 		message, err := bufio.NewReader(os.Stdin).ReadString('\n')
  73. 		if err == io.EOF {
  74. 			fmt.Fprint(conn, message)
  75. 			break
  76. 		} else if err != nil {
  77. 			fmt.Println("Error reading: ", err.Error())
  78. 			break
  79. 		} else {
  80. 			fmt.Fprintf(conn, message)
  81. 		}
  82. 	}
  83. }
  85. func usage(filename string) string {
  86. 	return fmt.Sprintf("Usage: %s <address (ex. localhost:8016, google.com:http, [2001:db8::1]:http, etc.)> [timeout (ex. 10s, 300ms, etc.)]", filename)
  87. }

我现在正在使用Windows 7。问题是什么，我该如何解决？

你可以在这里找到服务器端和客户端代码：
https://gist.github.com/programus/52591a97def30df9dc81

英文:

I am trying to build a very simple tcp server/client. And I want the program could close the connection when it is interrupted by ctrl-c.

If I only send message or only receive message in the main thread, everything works just fine.

Here is the code for the client side.

  1. package main 
  2. import (
  3. &quot;fmt&quot;
  4. &quot;os&quot;
  5. &quot;os/signal&quot;
  6. &quot;syscall&quot;
  7. &quot;net&quot;
  8. &quot;bufio&quot;
  9. &quot;io&quot;
  10. &quot;time&quot;
  11. )
  12. const (
  13. TIMEOUT = 10
  14. )
  15. func main() {
  16. if len(os.Args) &lt; 2 {
  17. fmt.Println(usage(os.Args[0]))
  18. return
  19. }
  20. var timeout time.Duration
  21. if len(os.Args) &gt; 2 {
  22. timeout, _ = time.ParseDuration(os.Args[2])
  23. }
  24. if timeout == 0 {
  25. timeout = time.Duration(TIMEOUT * time.Second)
  26. }
  27. conn, err := net.DialTimeout(&quot;tcp&quot;, os.Args[1], timeout)
  28. if err != nil {
  29. fmt.Println(&quot;Error connecting: &quot;, err.Error())
  30. return
  31. }
  32. defer conn.Close()
  33. c := make(chan os.Signal, 1)
  34. signal.Notify(c, syscall.SIGINT, syscall.SIGTERM)
  35. go func() {
  36. fmt.Println(&quot;wait ctrl-c&quot;)
  37. for _ = range c {
  38. fmt.Println(&quot;close on ctrl-c&quot;)
  39. conn.Close()
  40. }
  41. }()
  42. for {
  43. message, err := bufio.NewReader(os.Stdin).ReadString(&#39;\n&#39;)
  44. if err == io.EOF {
  45. fmt.Fprint(conn, message)
  46. break
  47. } else if err != nil {
  48. fmt.Println(&quot;Error reading: &quot;, err.Error())
  49. break
  50. } else {
  51. fmt.Fprintf(conn, message)
  52. }
  53. }
  54. }
  55. func usage(filename string) string {
  56. return fmt.Sprintf(&quot;Usage: %s &lt;address (ex. localhost:8016, google.com:http, [2001:db8::1]:http, etc.)&gt; [timeout (ex. 10s, 300ms, etc.)]&quot;, filename)
  57. }

But after I added the code that just print what it received and run it in another thread, the ctrl-c handler does not work.

This is the code:

  1. package main 
  2. import (
  3. &quot;fmt&quot;
  4. &quot;os&quot;
  5. &quot;os/signal&quot;
  6. &quot;syscall&quot;
  7. &quot;net&quot;
  8. &quot;bufio&quot;
  9. &quot;io&quot;
  10. &quot;time&quot;
  11. )
  12. const (
  13. TIMEOUT = 10
  14. )
  15. func main() {
  16. if len(os.Args) &lt; 2 {
  17. fmt.Println(usage(os.Args[0]))
  18. return
  19. }
  20. var timeout time.Duration
  21. if len(os.Args) &gt; 2 {
  22. timeout, _ = time.ParseDuration(os.Args[2])
  23. }
  24. if timeout == 0 {
  25. timeout = time.Duration(TIMEOUT * time.Second)
  26. }
  27. conn, err := net.DialTimeout(&quot;tcp&quot;, os.Args[1], timeout)
  28. if err != nil {
  29. fmt.Println(&quot;Error connecting: &quot;, err.Error())
  30. return
  31. }
  32. defer conn.Close()
  33. c := make(chan os.Signal, 1)
  34. signal.Notify(c, syscall.SIGINT, syscall.SIGTERM)
  35. go func() {
  36. fmt.Println(&quot;wait ctrl-c&quot;)
  37. for _ = range c {
  38. fmt.Println(&quot;close on ctrl-c&quot;)
  39. conn.Close()
  40. }
  41. }()
  42. // code added.
  43. go func() {
  44. for {
  45. message, err := bufio.NewReader(conn).ReadString(&#39;\n&#39;)
  46. if err == io.EOF {
  47. fmt.Print(message)
  48. break
  49. } else if err != nil {
  50. fmt.Println(&quot;Error remote reading: &quot;, err.Error())
  51. break
  52. } else {
  53. fmt.Print(message)
  54. }
  55. }
  56. conn.Close()
  57. os.Exit(0)
  58. }()
  59. for {
  60. message, err := bufio.NewReader(os.Stdin).ReadString(&#39;\n&#39;)
  61. if err == io.EOF {
  62. fmt.Fprint(conn, message)
  63. break
  64. } else if err != nil {
  65. fmt.Println(&quot;Error reading: &quot;, err.Error())
  66. break
  67. } else {
  68. fmt.Fprintf(conn, message)
  69. }
  70. }
  71. }
  72. func usage(filename string) string {
  73. return fmt.Sprintf(&quot;Usage: %s &lt;address (ex. localhost:8016, google.com:http, [2001:db8::1]:http, etc.)&gt; [timeout (ex. 10s, 300ms, etc.)]&quot;, filename)
  74. }

I am working on Windows 7 now.
What is the problem and how can I solve it?

You can find both server side and client side code here:
https://gist.github.com/programus/52591a97def30df9dc81

答案1

得分: 0

我进行了更多的调查，发现问题的关键不是线程，而是信号处理程序是否有足够的时间运行。

我编写了一个简单的程序，在Windows 7下重现了这个问题，并找到了解决方案。

  1. package main
  3. import (
  4. 	"fmt"
  5. 	"io"
  6. 	"os"
  7. 	"os/signal"
  8. )
  10. func main() {
  11. 	c := make(chan os.Signal, 1)
  12. 	//q := make(chan bool, 1)
  13. 	signal.Notify(c, os.Interrupt, os.Kill)
  14. 	
  15. 	go func() {
  16. 		sig := <-c
  17. 		fmt.Println(sig)
  18. 		//close(q)
  19. 	}()
  20. 	
  21. 	count, err := io.Copy(os.Stdout, os.Stdin)
  22. 	fmt.Println(count, err)
  23. 	//select {
  24. 	//case <-q:
  25. 	//}
  26. }

你会发现有时信号可能不会被打印出来。但是当我取消注释与q通道相关的代码后，它总是正常工作。

所以我认为这可能是因为程序退出得太快，没有足够的时间让信号处理程序运行。

希望这个问答能帮助其他遇到同样问题的人。

另外，我解决了简单的TCP服务器/客户端问题，并更新了代码片段。

https://gist.github.com/programus/52591a97def30df9dc81

英文:

I did some more investigation and I found that the key point of the problem is not the threads but whether there is enough time for signal handler running.

I made a simple program to re-produce the problem under Windows 7 as well as the solution.

  1. package main
  2. import (
  3. &quot;fmt&quot;
  4. &quot;io&quot;
  5. &quot;os&quot;
  6. &quot;os/signal&quot;
  7. )
  8. func main() {
  9. c := make(chan os.Signal, 1)
  10. //q := make(chan bool, 1)
  11. signal.Notify(c, os.Interrupt, os.Kill)
  12. go func() {
  13. sig := &lt;- c
  14. fmt.Println(sig)
  15. //close(q)
  16. }()
  17. count, err := io.Copy(os.Stdout, os.Stdin)
  18. fmt.Println(count, err)
  19. //select {
  20. //case &lt;- q:
  21. //}
  22. }

You will find the signal might not be printed out sometime. But after I uncommented the q channel related code. It always works.

So I think it would because the program quit too quickly to let the signal handler run.

Hope this Q&A could help others who has the same problem.

Also, I worked out a solution for the simple tcp server/client and updated the gist.

https://gist.github.com/programus/52591a97def30df9dc81

huangapple
  • 本文由 发表于 2015年9月9日 15:53:20
  • 转载请务必保留本文链接：https://go.coder-hub.com/32473923.html
  • go
  • signals
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