在进行HTTP请求时出现了错误。

huangapple
go评论131阅读模式
英文:

go error on doing HTTP requests

问题

当运行以下HTTP客户端对Web服务器进行压力测试时，出现了奇怪的错误，想知道是什么原因。Go的版本是go1.8.1 linux/amd64，运行在Ubuntu 14.04上，内存为16GB。

以下是代码运行时的输出：

  1. $ go run te2.go 
  2. 563.904492ms
  3. Get http://10.3.0.6/small: dial tcp 10.3.0.6:80: connect: cannot assign requested address
  4. Get http://10.3.0.6/small: dial tcp 10.3.0.6:80: connect: cannot assign requested address
  5. Get http://10.3.0.6/small: dial tcp 10.3.0.6:80: connect: cannot assign requested address
  6. panic: runtime error: invalid memory address or nil pointer dereference
  7. [signal SIGSEGV: segmentation violation code=0x1 addr=0x40 pc=0x5e3b27]
  9. goroutine 140284 [running]:
  10. main.httpGet(0x0)
  11.     /home/jon/learn/go/te2.go:27 +0x107
  12. created by main.main
  13.     /home/jon/learn/go/te2.go:45 +0xd3
  14. panic: runtime error: invalid memory address or nil pointer dereference
  15. [signal SIGSEGV: segmentation violation code=0x1 addr=0x40 pc=0x5e3b27]
  17. goroutine 140375 [running]:
  18. main.httpGet(0x0)
  19.     /home/jon/learn/go/te2.go:27 +0x107
  20. created by main.main
  21.     /home/jon/learn/go/te2.go:45 +0xd3
  22. exit status 2

有什么想法吗？

以下是代码片段：

  1. package main
  3. import "fmt"
  4. import "bufio"
  5. import "os"
  6. import "time"
  7. import "net/http"
  9. var req = []byte("GET /small HTTP/1.1\r\n" +
  10. 	"Host: localhost\r\n" +
  11. 	"Content-Length: 0\r\n\r\n")
  12. var buf = make([]byte, 1024)
  13. var total = 0
  14. var t0 = time.Now()
  15. var c = make(chan int)
  17. func httpGet() int {
  18. 	req, err := http.NewRequest("GET", "http://10.3.0.6/small", nil)
  19. 	//req.Header.Add("User-Agent", `MYCLIENT`)
  20. 	//req.Header.Add("Cookie", `sessid=12345`)
  21. 	client := &http.Client{}
  22. 	resp, err := client.Do(req)
  23. 	//defer resp.Body.Close()
  24. 	if err != nil {
  25. 		fmt.Println(err)
  26. 	}
  27. 	resp.Body.Close()
  28. 	total++
  29. 	if total == 10000 {
  30. 		fmt.Println(time.Now().Sub(t0))
  31. 	}
  32. 	c <- 1
  33. 	return 0
  34. }
  36. func main() {
  37. 	i := 1
  38. 	t0 = time.Now()
  39. 	for i < 1000 {
  40. 		go httpGet()
  41. 		i += 1
  42. 	}
  43. 	for 1 < 2 {
  44. 		<-c
  45. 		go httpGet()
  46. 	}
  47. 	reader := bufio.NewReader(os.Stdin)
  48. 	text, _ := reader.ReadString('\n')
  49. 	fmt.Println(text)
  50. }
英文:

When running the following http client to stress test a web server, got strange error, wonder what was the cause. The version of go is go1.8.1 linux/amd64 running on Ubuntu 14.04 with 16GB of ram.

  1. $ go run te2.go 
  2. 563.904492ms
  3. Get http://10.3.0.6/small: dial tcp 10.3.0.6:80: connect: cannot assign requested address
  4. Get http://10.3.0.6/small: dial tcp 10.3.0.6:80: connect: cannot assign requested address
  5. Get http://10.3.0.6/small: dial tcp 10.3.0.6:80: connect: cannot assign requested address
  6. panic: runtime error: invalid memory address or nil pointer dereference
  7. [signal SIGSEGV: segmentation violation code=0x1 addr=0x40 pc=0x5e3b27]
  9. goroutine 140284 [running]:
  10. main.httpGet(0x0)
  11.     /home/jon/learn/go/te2.go:27 +0x107
  12. created by main.main
  13.     /home/jon/learn/go/te2.go:45 +0xd3
  14. panic: runtime error: invalid memory address or nil pointer dereference
  15. [signal SIGSEGV: segmentation violation code=0x1 addr=0x40 pc=0x5e3b27]
  17. goroutine 140375 [running]:
  18. main.httpGet(0x0)
  19.     /home/jon/learn/go/te2.go:27 +0x107
  20. created by main.main
  21.     /home/jon/learn/go/te2.go:45 +0xd3
  22. exit status 2

any ideas?

Here is the code snippet:

  1. package main
  3. import &quot;fmt&quot;
  4. import &quot;bufio&quot;
  5. import &quot;os&quot;
  6. import &quot;time&quot;
  7. import &quot;net/http&quot;
  9. var req = []byte(&quot;GET /small HTTP/1.1\r\n&quot; +
  10. &quot;Host: localhost\r\n&quot; +
  11. &quot;Content-Length: 0\r\n\r\n&quot;);
  12. var buf = make([]byte, 1024)
  13. var total = 0;
  14. var t0 = time.Now()
  15. var c = make(chan int)
  17. func httpGet ()  int {
  18. 	req, err := http.NewRequest(&quot;GET&quot;, &quot;http://10.3.0.6/small&quot;, nil)
  19. 	//req.Header.Add(&quot;User-Agent&quot;, `MYCLIENT`)
  20. 	//req.Header.Add(&quot;Cookie&quot;, `sessid=12345`)
  21. 	client := &amp;http.Client{}
  22. 	resp, err := client.Do(req)
  23. 	//defer resp.Body.Close()
  24. 	if (err != nil) {
  25. 		fmt.Println(err)
  26. 	}
  27. 	resp.Body.Close()
  28. 	total ++
  29. 	if (total == 10000) {
  30. 		fmt.Println(time.Now().Sub(t0))
  31. 	}
  32. 	c &lt;- 1
  33. 	return 0;
  34. }
  36. func main() {
  37. 	i := 1
  38. 	t0 = time.Now()
  39. 	for (i &lt; 1000) {
  40. 		go httpGet()
  41. 		i += 1
  42. 	}
  43. 	for (1 &lt; 2) {
  44. 		&lt;-c
  45. 		go httpGet()
  46. 	}
  47. 	reader := bufio.NewReader(os.Stdin)
  48. 	text, _ := reader.ReadString(&#39;\n&#39;)
  49.     fmt.Println(text)	
  50. }

答案1

得分: 3

在这个片段中，你正在检查err并继续执行。

所以如果发生了某些事情，err不是nil，但resp（或resp.Body）是nil指针-你会打印错误然后解引用一个空指针。

你应该这样做：如果发生错误-清理并从函数中返回。

英文: 
  1. resp, err := client.Do(req)
  2. //defer resp.Body.Close()
  3. if (err != nil) {
  4.     fmt.Println(err)
  5. }
  6. resp.Body.Close()

In this fragment you're checking the err and continue execution.

So if something happened and the err is not nil, but resp is (or the resp.Body is) - you print the error then dereference a nil pointer.

What you should have done: if an error occurs - cleanup and return from the function.

huangapple
  • 本文由 发表于 2017年5月8日 11:03:27
  • 转载请务必保留本文链接：https://go.coder-hub.com/43839145.html
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