How to return a custom user friendly error message in Kubernetes?

huangapple
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英文:

How to return a custom user friendly error message in Kubernetes?

问题

我有一个使用Golang与Kubernetes通信的后端。我想重新构造从Kubernetes获取的错误响应，并将其发送到前端。

当用户添加一个无效的名称或已存在的名称时，我希望返回有意义的验证错误消息...

而且我希望是通用的，而不是在每个端点的控制器中硬编码。

我正在使用kubernetes/client-go。

  1. 第一个错误：

例如，假设我想将一个酒店添加到etcd中，当我尝试添加酒店的名称：hotel123时，它已经存在。

  • 我得到这个错误消息：\"hotel123\" already exists。
  • 我想要的是：hotel123 already exists。
  1. 第二个错误：

例如，假设我想将一个酒店添加到etcd中，当我尝试添加酒店的名称：hotel_123时，它已经存在。

  • 我得到这个错误消息：\"hotel_123\" is invalid, Invalid value: \"hotel_123\"...
  • 我想要的是：hotel_123 is invalid

如何返回自定义的用户友好错误消息？

PS：我有多个函数，所以验证应该是通用的。

英文:

I have a backend with golang that talks to k8s. I want to reformulate the error response that i get from k8s and send it to the frontend.

I want to return a meaningful validation error messages for the user, when he add a non valid name, something already exist ...

And i want something generic not hardcoded in each endpoint's controller.

I am using kubernetes/client-go.

  1. First error:

For example lets say i want to add a hotel to the etcd, when i try to add the hotel's name: hotel123, that's already exist.

  • I get this error message: \"hotel123\" already exists.
  • What i want : hotel123 already exists.
  1. second error:

For example lets say i want to add a hotel to the etcd, when i try to add the hotel name: hotel_123, that's alerady exist.

  • I get this error message: \"hotel_123\" is invalid, Invalid value: \"hotel_123\"...
  • What i want: hotel_123 is invalid

How to return a custom user friendly error message ?

PS: i have multiple functions, so the validation should be generic.

答案1

得分: 1

通常情况下（虽然有一些变通方法），如果你想捕获错误以返回更有用的错误信息，你需要确保满足以下条件：

  1. 你要捕获的错误具有有意义的类型。
  2. 你使用的 Go 版本 >= 1.13，其中包含了有用的辅助函数。

下面的示例中，我试图读取一个不存在的配置文件。我的代码检查返回的错误是否为 fs.PathError 类型，然后抛出自己更有用的错误。你可以根据你的用例扩展这个通用思路。

  1. package main
  3. import (
  4. 	"errors"
  5. 	"fmt"
  6. 	"io/fs"
  8. 	"k8s.io/client-go/tools/clientcmd"
  9. )
  11. func main() {
  13. 	var myError error
  14. 	config, originalError := clientcmd.BuildConfigFromFlags("", "/some/path/that/doesnt/exist")
  15. 	if originalError != nil {
  17. 		var pathError *fs.PathError
  19. 		switch {
  20. 		case errors.As(originalError, &pathError):
  22. 			myError = fmt.Errorf("there is no config file at %s", originalError.(*fs.PathError).Path)
  24. 		default:
  26. 			myError = fmt.Errorf("there was an error and its type was %T", originalError)
  28. 		}
  30. 		fmt.Printf("%#v", myError)
  32. 	} else {
  34. 		fmt.Println("There was no error")
  35. 		fmt.Println(config)
  37. 	}
  39. }

在调试过程中，你会发现 %T 格式化符号非常有用。

对于你的特定用例，你可以使用正则表达式来解析所需的文本。

下面的正则表达式表示：

  1. ^\W* 以任意非字母数字字符开头
  2. (\w+) 捕获后面的字母数字字符串
  3. \W*\s? 匹配非字母数字字符
  4. (is\sinvalid) 捕获 "is invalid"
  1. func MyError(inError error) error {
  2. 	pattern, _ := regexp.Compile(`^\W*(\w+)\W*\s?(is\sinvalid)(.*)$`)
  3. 	myErrorString := pattern.ReplaceAll([]byte(inError.Error()), []byte("$1 $2"))
  4. 	return errors.New(string(myErrorString))
  5. }

在这个 playground 上可以看到示例：

https://goplay.tools/snippet/bcZO7wa8Vnl

英文:

In general (although there are workarounds), if you want to trap an error in order to return a more useful error, you want to ensure the following conditions are met:

  1. The error you're trapping has a meaningful type
  2. You're using go version >= 1.13 which ships with useful helper functions

In the following example I'm trying to read a config file that doesn't exist. My code checks that the error returned is a fs.PathError and then throws it's own more useful error. You can extend this general idea to your use case.

  1. package main
  3. import (
  4. 	"errors"
  5. 	"fmt"
  6. 	"io/fs"
  8. 	"k8s.io/client-go/tools/clientcmd"
  9. )
  11. func main() {
  13. 	var myError error
  14. 	config, originalError := clientcmd.BuildConfigFromFlags("", "/some/path/that/doesnt/exist")
  15. 	if originalError != nil {
  17. 		var pathError *fs.PathError
  19. 		switch {
  20. 		case errors.As(originalError, &pathError):
  22. 			myError = fmt.Errorf("there is no config file at %s", originalError.(*fs.PathError).Path)
  24. 		default:
  26. 			myError = fmt.Errorf("there was an error and it's type was %T", originalError)
  28. 		}
  30. 		fmt.Printf("%#v", myError)
  32. 	} else {
  34. 		fmt.Println("There was no error")
  35. 		fmt.Println(config)
  37. 	}
  39. }

In your debugging, you will find the %T formatter useful.

For your specific use-case, you can use a Regex to parse out the desired text.

The regex below says:

  1. ^\W* start with any non-alhpanumeric characters
  2. (\w+) capture the alphanumeric string following
  3. \W*\s? match non-alphanumeric characters
  4. (is\sinvalid) capture "is invalid"
  1. func MyError(inError error) error {
  2.  	pattern, _ := regexp.Compile(`^\W*(\w+)\W*\s?(is\sinvalid)(.*)$`)
  3.    	myErrorString := pattern.ReplaceAll([]byte(inError.Error()), []byte("$1 $2"))
  4.    	return errors.New(string(myErrorString))
  5. }

As seen on this playground:

https://goplay.tools/snippet/bcZO7wa8Vnl

答案2

得分: 1

err.Error()是从Kubernetes服务器获取的原始、有意义且最好的错误消息，用于向用户提供（或者您可以自己翻译）。

解释：

您需要深入了解kubernetes/client-go客户端库。

每个客户端通过HTTP REST API与K8s服务器进行通信，服务器以json格式返回响应。如果可能的话，client-go库会解码响应体并将结果存储到对象中。

对于您的情况，让我通过Namespace资源给您举几个例子：

  1. 第一个错误：
  1. POST https://xxx.xx.xx.xx:6443/api/v1/namespaces?fieldManager=kubectl-create
  2. 响应状态：409 Conflict
  3. {
  4.   "kind": "Status",
  5.   "apiVersion": "v1",
  6.   "metadata": {},
  7.   "status": "Failure",
  8.   "message": "namespaces \"hotel123\" already exists",
  9.   "reason": "AlreadyExists",
  10.   "details": {
  11.     "name": "hotel123",
  12.     "kind": "namespaces"
  13.   },
  14.   "code": 409
  15. }
  1. 第二个错误：
  1. POST https://xxx.xx.xx.xx:6443/api/v1/namespaces?fieldManager=kubectl-create
  2. 响应状态：422 Unprocessable Entity
  3. {
  4.     "kind": "Status",
  5.     "apiVersion": "v1",
  6.     "metadata": {},
  7.     "status": "Failure",
  8.     "message": "Namespace \"hotel_123\" is invalid: metadata.name: Invalid value: \"hotel_123\": a lowercase RFC 1123 label must consist of lower case alphanumeric characters or '-', and must start and end with an alphanumeric character (e.g. 'my-name',  or '123-abc', regex used for validation is '[a-z0-9]\r\n([-a-z0-9]*[a-z0-9])?')",
  9.     "reason": "Invalid",
  10.     "details": {
  11.         "name": "hotel_123",
  12.         "kind": "Namespace",
  13.         "causes": [
  14.             {
  15.                 "reason": "FieldValueInvalid",
  16.                 "message": "Invalid value: \"hotel_123\": a lowercase RFC 1123 label must consist of lower case alphanumeric characters or '-', and must start and end with an alphanumeric character (e.g. 'my-name',  or '123-abc', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?')",
  17.                 "field": "metadata.name"
  18.             }
  19.         ]
  20.     },
  21.     "code": 422
  22. }
  1. 正常返回：
  1. POST https://xxx.xx.xx.xx:6443/api/v1/namespaces?fieldManager=kubectl-create
  2. 响应状态：201 Created
  3. {
  4.     "kind": "Namespace",
  5.     "apiVersion": "v1",
  6.     "metadata": {
  7.         "name": "hotel12345",
  8.         "uid": "7a301d8b-37cd-45a5-8345-82wsufy88223456",
  9.         "resourceVersion": "12233445566",
  10.         "creationTimestamp": "2023-04-03T15:35:59Z",
  11.         "managedFields": [
  12.             {
  13.                 "manager": "kubectl-create",
  14.                 "operation": "Update",
  15.                 "apiVersion": "v1",
  16.                 "time": "2023-04-03T15:35:59Z",
  17.                 "fieldsType": "FieldsV1",
  18.                 "fieldsV1": {
  19.                     "f:status": {
  20.                         "f:phase": {}
  21.                     }
  22.                 }
  23.             }
  24.         ]
  25.     },
  26.     "spec": {
  27.         "finalizers": [
  28.             "kubernetes"
  29.         ]
  30.     },
  31.     "status": {
  32.         "phase": "Active"
  33.     }
  34. }

简而言之，如果HTTP状态不是2xx，返回的对象类型是Status且.Status != StatusSuccess，则会使用Status中的附加信息（在本例中为message）来丰富错误，就像下面的代码片段一样：

  1. createdNamespace, err := clientset.CoreV1().Namespaces().Create(context.TODO(), namespace, metav1.CreateOptions{})
  2. if err != nil {
  3.     // 打印“namespaces "hotel123" already exists”或类似的消息
  4.     fmt.Println(err.Error())
  5.     return err.Error()
  6. }
  7. fmt.Printf("在集群中创建了Namespace %+v\n", createdNamespace)
  8. return ""
英文:

String err.Error() is the original, meaningful and best error message you can get from Kubernetes server for the user (Or you have to translate it by yourself).

Explains:

You need to look beyond the surface of kubernetes/client-go client library.

Each client talks to k8s server through HTTP REST APIs, which sends back response in json. It's the client-go library that decodes the response body and stores the result into object, if possible.

As for your case, let me give you some examples through the Namespace resource:

  1. First error:
  1. POST https://xxx.xx.xx.xx:6443/api/v1/namespaces?fieldManager=kubectl-create
  2. Response Status: 409 Conflict
  3. {
  4.   "kind": "Status",
  5.   "apiVersion": "v1",
  6.   "metadata": {},
  7.   "status": "Failure",
  8.   "message": "namespaces \"hotel123\" already exists",
  9.   "reason": "AlreadyExists",
  10.   "details": {
  11.     "name": "hotel123",
  12.     "kind": "namespaces"
  13.   },
  14.   "code": 409
  15. }
  1. second error:
  1. POST https://xxx.xx.xx.xx:6443/api/v1/namespaces?fieldManager=kubectl-create
  2. Response Status: 422 Unprocessable Entity
  3. {
  4.     "kind": "Status",
  5.     "apiVersion": "v1",
  6.     "metadata": {},
  7.     "status": "Failure",
  8.     "message": "Namespace \"hotel_123\" is invalid: metadata.name: Invalid value: \"hotel_123\": a lowercase RFC 1123 label must consist of lower case alphanumeric characters or '-', and must start and end with an alphanumeric character (e.g. 'my-name',  or '123-abc', regex used for validation is '[a-z0-9]\r\n([-a-z0-9]*[a-z0-9])?')",
  9.     "reason": "Invalid",
  10.     "details": {
  11.         "name": "hotel_123",
  12.         "kind": "Namespace",
  13.         "causes": [
  14.             {
  15.                 "reason": "FieldValueInvalid",
  16.                 "message": "Invalid value: \"hotel_123\": a lowercase RFC 1123 label must consist of lower case alphanumeric characters or '-', and must start and end with an alphanumeric character (e.g. 'my-name',  or '123-abc', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?')",
  17.                 "field": "metadata.name"
  18.             }
  19.         ]
  20.     },
  21.     "code": 422
  22. }
  1. normal return:
  1. POST https://xxx.xx.xx.xx:6443/api/v1/namespaces?fieldManager=kubectl-create
  2. Response Status: 201 Created
  3. {
  4.     "kind": "Namespace",
  5.     "apiVersion": "v1",
  6.     "metadata": {
  7.         "name": "hotel12345",
  8.         "uid": "7a301d8b-37cd-45a5-8345-82wsufy88223456",
  9.         "resourceVersion": "12233445566",
  10.         "creationTimestamp": "2023-04-03T15:35:59Z",
  11.         "managedFields": [
  12.             {
  13.                 "manager": "kubectl-create",
  14.                 "operation": "Update",
  15.                 "apiVersion": "v1",
  16.                 "time": "2023-04-03T15:35:59Z",
  17.                 "fieldsType": "FieldsV1",
  18.                 "fieldsV1": {
  19.                     "f:status": {
  20.                         "f:phase": {}
  21.                     }
  22.                 }
  23.             }
  24.         ]
  25.     },
  26.     "spec": {
  27.         "finalizers": [
  28.             "kubernetes"
  29.         ]
  30.     },
  31.     "status": {
  32.         "phase": "Active"
  33.     }
  34. }

In a word, if the HTTP Status is not 2xx, the returned object is of type Status and has .Status != StatusSuccess, the additional information(message in this case) in Status will be used to enrich the error, just as the code snippets below:

  1. createdNamespace, err := clientset.CoreV1().Namespaces().Create(context.TODO(), namespace, metav1.CreateOptions{})
  2. if err != nil {
  3.     // print "namespaces \"hotel123\" already exists" or so
  4. 	fmt.Println(err.Error())
  5.     return err.Error()
  6. }
  7. fmt.Printf("Created Namespace %+v in the cluster\n", createdNamespace)
  8. return ""

huangapple
  • 本文由 发表于 2023年3月28日 16:07:25
  • 转载请务必保留本文链接：https://go.coder-hub.com/75863744.html
  • client-go
  • etcd
  • go
  • kubernetes
  • kubernetes-custom-resources
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