如何解決當我嘗試將慢速日誌發佈到 CloudWatch Logs 時在 CloudFormation 中收到的錯誤？

簡短描述

若要解決此錯誤，請在日誌群組層級使用單獨的政策，以允許 Amazon Elasticsearch Service (Amazon ES) 將日誌推送到 CloudWatch Logs。然後，使用 AWS::Elasticsearch::Domain 中的 AccessPolicies 為 Amazon ES 網域設定權限。

下列步驟說明如何使用以 Python 3.6 建立的 AWS Lambda 支援的自訂資源，將慢速日誌發佈到使用 CloudFormation 的 CloudWatch。自訂資源會觸發 Lambda 函數，然後該函數會觸發 PutResourcePolicy API 以發佈慢速日誌。

**注意：**當 CloudFormation 啟用日誌發佈到 CloudWatch 時，AWS::Logs::LogGroup 資源沒有可指派資源存取政策的屬性。為 CloudWatch Logs 日誌群組指定的資源存取政策應授予足夠的權限，讓 Amazon ES 發佈日誌串流。您無法直接使用 CloudFormation 資源建立存取政策權限。這是因為 AWS::Logs::LogGroup 資源的 PutResourcePolicy API 呼叫不受 CloudFormation 支援。

解決方法

**注意：**如果您在執行 AWS Command Line Interface (AWS CLI) 命令時收到錯誤訊息，請確認您使用的是最新的 AWS CLI 版本。

下列 CloudFormation 範本使用自訂資源來取得日誌群組的名稱。然後，範本會套用允許 Amazon ES 服務對日誌群組進行 API 呼叫的政策。

1.    建立一個名為 ESlogsPermission.yaml 的 CloudFormation 範本：

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Permission is hereby granted, free of charge, to any person obtaining a copy of this
software and associated documentation files (the "Software"), to deal in the Software
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
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HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

AWSTemplateFormatVersion: 2010-09-09
Description: AWS cloudFormation template to publish slow logs to Amazon CloudWatch Logs.
Parameters:
  LogGroupName:
    Type: String
    Description: Please don't change the log group name while updating
  ESDomainName:
    Description: A name for the Amazon Elastic Search domain
    Type: String
  LambdaFunctionName:
    Description: Lambda Function Name
    Type: String
Resources:
  AwsLogGroup:
    Type: 'AWS::Logs::LogGroup'
    Properties:
      LogGroupName: !Ref LogGroupName
  LambdaLogGroup:
    Type: 'AWS::Logs::LogGroup'
    Properties:
      LogGroupName: !Sub '/aws/lambda/${LambdaFunctionName}'
  LambdaExecutionRole:
    Type: 'AWS::IAM::Role'
    Properties:
      AssumeRolePolicyDocument:
        Version: 2012-10-17
        Statement:
          - Effect: Allow
            Principal:
              Service:
                - lambda.amazonaws.com
            Action:
              - 'sts:AssumeRole'
      Path: /
      Policies:
        - PolicyName: root1
          PolicyDocument:
            Version: 2012-10-17
            Statement:
              - Effect: Allow
                Action:
                  - 'logs:CreateLogStream'
                  - 'logs:PutLogEvents'
                Resource: !Sub >-
                  arn:aws:logs:${AWS::Region}:${AWS::AccountId}:log-group:/aws/lambda/${LambdaFunctionName}:log-stream:*
        - PolicyName: root2
          PolicyDocument:
            Version: 2012-10-17
            Statement:
              - Effect: Allow
                Action:
                  - 'logs:CreateLogGroup'
                Resource:
                  - !Sub >-
                    arn:aws:logs:${AWS::Region}:${AWS::AccountId}:log-group:/aws/lambda/${LambdaFunctionName}
                  - !Sub >-
                    arn:aws:logs:${AWS::Region}:${AWS::AccountId}:log-group:/${LogGroupName}
              - Effect: Allow
                Action:
                  - 'logs:PutResourcePolicy'
                  - 'logs:DeleteResourcePolicy'
                Resource: !Sub 'arn:aws:logs:${AWS::Region}:${AWS::AccountId}:*'
  logGroupPolicyFunction:
    DependsOn: LambdaLogGroup
    Type: 'AWS::Lambda::Function'
    Properties:
      FunctionName: !Ref LambdaFunctionName
      Code:
        ZipFile: >
          import urllib3

          import json

          import boto3

          http = urllib3.PoolManager()

          SUCCESS = "SUCCESS"

          FAILED = "FAILED"

          def send(event, context, responseStatus, responseData,
          physicalResourceId=None, noEcho=False):
              responseUrl = event['ResponseURL']
              print(responseUrl)
              responseBody = {}
              responseBody['Status'] = responseStatus
              responseBody['Reason'] = 'See the details in CloudWatch Log Stream: ' + context.log_stream_name
              responseBody['PhysicalResourceId'] = physicalResourceId or context.log_stream_name
              responseBody['StackId'] = event['StackId']
              responseBody['RequestId'] = event['RequestId']
              responseBody['LogicalResourceId'] = event['LogicalResourceId']
              responseBody['NoEcho'] = noEcho
              responseBody['Data'] = responseData
              json_responseBody = json.dumps(responseBody)
              print("Response body:\n" + json_responseBody)
              headers = {
                  'content-type' : '',
                  'content-length' : str(len(json_responseBody))
              }
              try:
                  response = http.request('PUT',responseUrl,body=json_responseBody.encode('utf-8'),headers=headers)
                  print("Status code: " + response.reason)
              except Exception as e:
                  print("send(..) failed executing requests.put(..): " + str(e))
          def handler(event, context):
              logsgroup_policy_name=event['ResourceProperties']['CWLOGS_NAME']
              cw_log_group_arn=event['ResourceProperties']['CWLOG_ARN']
              cwlogs = boto3.client('logs')
              loggroup_policy={
                  "Version": "2012-10-17",
                  "Statement": [{
                  "Sid": "",
                  "Effect": "Allow",
                  "Principal": { "Service": "es.amazonaws.com"},
                  "Action":[
                  "logs:PutLogEvents",
                  " logs:PutLogEventsBatch",
                  "logs:CreateLogStream"
                      ],
                  'Resource': f'{cw_log_group_arn}'
                  }]
                  }
              loggroup_policy = json.dumps(loggroup_policy)
              if(event['RequestType'] == 'Delete'):
                  print("Request Type:",event['RequestType'])
                  cwlogs.delete_resource_policy(
                  policyName=logsgroup_policy_name
                 )
                  responseData={}
                  send(event, context, SUCCESS, responseData)
              elif(event['RequestType'] == 'Create'):
                  try:
                      cwlogs.put_resource_policy(
                      policyName = logsgroup_policy_name,
                      policyDocument = loggroup_policy
                       )
                      responseData={}
                      print("Sending response to custom resource")
                      send(event, context, SUCCESS, responseData)
                  except Exception as  e:
                      print('Failed to process:', e)
                      send(event, context, FAILED, responseData)
              elif(event['RequestType'] == 'Update'):
                  try:
                      responseData={}
                      print("Update is not supported on this resource")
                      send(event, context, SUCCESS, responseData)
                  except Exception as  e:
                      print('Failed to process:', e)
                      send(event, context, FAILED, responseData)
      Handler: index.handler
      Role: !GetAtt
        - LambdaExecutionRole
        - Arn
      Runtime: python3.6
  logGroupPolicycustomresource:
    Type: 'Custom::LogGroupPolicy'
    Properties:
      ServiceToken: !GetAtt
        - logGroupPolicyFunction
        - Arn
      CWLOGS_NAME: !Ref LogGroupName
      CWLOG_ARN: !GetAtt
        - AwsLogGroup
        - Arn
  ElasticsearchDomain:
    Type: 'AWS::Elasticsearch::Domain'
    DependsOn: logGroupPolicycustomresource
    Properties:
      DomainName: !Ref ESDomainName
      ElasticsearchVersion: '6.2'
      EBSOptions:
        EBSEnabled: true
        VolumeSize: 10
        VolumeType: gp2
      LogPublishingOptions:
        SEARCH_SLOW_LOGS:
          CloudWatchLogsLogGroupArn: !GetAtt
            - AwsLogGroup
            - Arn
          Enabled: true

2.    若要啟動具有 ESlogsPermission.yaml 檔案的 CloudFormation 堆疊，請使用 CloudFormation 主控台或下列 AWS CLI 命令：

aws cloudformation create-stack --stack-name yourStackName --template-body file://yourTemplateName --parameters ParameterKey=LogGroupName,ParameterValue=Your-LogGroup-Name, ParameterKey=ESDomainName,ParameterValue=Your-ES-Name --capabilities CAPABILITY_NAMED_IAM --region yourRegion

**注意：**使用您的值取代 yourStackName、yourTemplateName、Your-LogGroup-Name、Your-ES-Name 及 yourRegion。

CloudFormation 範本會為您執行下列作業：

1.    建立日誌群組。

2.    建立 Lambda 函數。Lambda 函數會使用自訂資源，從 CloudFormation 範本的參數區段取得日誌群組名稱。Lambda 函數會為日誌群組名稱呼叫 PutResourcePolicy API。日誌群組必須具有允許 Amazon ES 網域放置日誌的政策。

3.    建立 Lambda 支援的自訂資源，以叫用在步驟 2 中建立的 Lambda 函數。自訂資源可協助在日誌群組 Amazon Resource Name (ARN) 上套用 PutResourcePolicy，以便 Amazon ES 可以串流日誌。在範本中，CloudFormation 使用自訂資源建立具有 LogPublishingOption 的 Amazon ES 網域。

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