Question

在控制台上创建只读副本时，可以使用多可用区部署。 AWS also announced last year只读副本支持MutliAZ

但是，当尝试在Cloudformation中复制它时，出现此错误

这是我Cloudformation中的摘录：

Resources:
  MasterDB:
    Type: AWS::RDS::DBInstance
    Properties:
      AllocatedStorage: 100
      BackupRetentionPeriod: 10
      DBInstanceClass: !Ref DBInstanceClass
      Engine: postgres
      EngineVersion: '10.6'
      MasterUsername: !Ref DBUsername
      MasterUserPassword: !Ref DBPassword
      MultiAZ: false 
      PubliclyAccessible: true

  ReplicaDB:
    Type: AWS::RDS::DBInstance
    Properties:
      DBInstanceClass: !Ref DBInstanceClass
      SourceDBInstanceIdentifier: !Ref MasterDB
      MultiAZ: true
      PubliclyAccessible: true

在documentation中，它指出：

将只读副本创建为多可用区数据库实例独立于源数据库是否为多可用区数据库实例。

...因此MasterDB未设置为MultiAZ应该不是问题。

我的Cloudformation模板是否有错误？还是Cloudformation不支持MultiAZ for Read Replicas？

谢谢！

Answer 1

我有同样的问题。我能够解决的唯一方法是在CloudFormation中使用自定义资源lambda。 lambda获取数据库实例的ID（在本例中为副本ID），然后使用boto3将其更改为Multi-Az副本。

这是lambda函数的模板：

# Create a python lambda function which 
# can enable Multi-AZ for read replicas.
#
# This lambda is meant to be executed by custom resource
# from other template in CloudFormaton
---

Resources:

    EnableMultiAz:
        Type: AWS::Lambda::Function
        Properties:
            Description: Create an AMI of an instance
            FunctionName: EnableMultiAzForDBInstance
            Handler: index.lambda_handler
            Role: !GetAtt LambdaExecutionRole.Arn
            Runtime: python3.7
            Timeout: 60
            Code: 
                ZipFile: |
                    import json
                    import boto3
                    import logging
                    import time

                    from botocore.vendored import requests

                    logger = logging.getLogger()
                    logger.setLevel(logging.INFO)

                    SUCCESS = "SUCCESS"
                    FAILED = "FAILED"

                    # from https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/cfn-lambda-function-code-cfnresponsemodule.html
                    def send(event, context, responseStatus, responseData, physicalResourceId=None, noEcho=False):

                        responseUrl = event['ResponseURL']

                        print(responseUrl)

                        responseBody = {
                            'Status': responseStatus,
                            'Reason': 'See ' + context.log_stream_name,
                            'PhysicalResourceId': physicalResourceId or context.log_stream_name,
                            'StackId': event['StackId'],
                            'RequestId': event['RequestId'],
                            'LogicalResourceId': event['LogicalResourceId'],
                            'NoEcho': noEcho,
                            'Data': responseData
                        }

                        json_responseBody = json.dumps(responseBody)

                        print("Response body:\n" + json_responseBody)

                        headers = {
                            'content-type' : '',
                            'content-length' : str(len(json_responseBody))
                        }

                        try:
                            response = requests.put(responseUrl,
                                                    data=json_responseBody,
                                                    headers=headers)
                            print("Status code: " + response.reason)
                        except Exception as e:
                            print("send(..) failed executing requests.put(..): " + str(e))

                    def lambda_handler(event, context):

                        print('event: ', json.dumps(event))

                        try:

                            return_data = {}

                            if 'RequestType' in event:

                                rds = boto3.client('rds')

                                dbinstance_id = event['ResourceProperties']['DBinstanceId'] 

                                if event['RequestType'] == 'Create':   

                                    r = rds.modify_db_instance(
                                            DBInstanceIdentifier=dbinstance_id, 
                                            MultiAZ=True, ApplyImmediately=True)        
                            send(event, context, SUCCESS, return_data)            

                        except Exception as e:
                            logger.error('custom response lambda failed due to: ' + str(e))
                            send(event, context, FAILED, {})


    LambdaExecutionRole:
        Type: AWS::IAM::Role
        Properties:
            RoleName: lambda-execution-role-with-rds
            AssumeRolePolicyDocument:
                Version: '2012-10-17'               
                Statement:
                    - Effect: Allow
                      Principal: {'Service': ['lambda.amazonaws.com']}
                      Action: ['sts:AssumeRole']
            ManagedPolicyArns:
                - arn:aws:iam::aws:policy/AWSLambdaExecute
            Path: '/'
            Policies:
                - PolicyName: PassRolePolicy
                  PolicyDocument: 
                      Version: "2012-10-17"
                      Statement: 
                          - Effect: "Allow"
                            Action: "iam:PassRole"
                            Resource: "*"
                - PolicyName: EnableMultiAZReadReplica
                  PolicyDocument: 
                      Version: "2012-10-17"
                      Statement: 
                          - Effect: "Allow"
                            Action: 
                                - "rds:ModifyDBInstance"                           
                            Resource: "*"                            



Outputs:

    LambdaArn:
        Value: !GetAtt EnableMultiAz.Arn

    LambdaRoleArn:
        Value: !GetAtt LambdaExecutionRole.Arn

您将此lambda模板放置在S3中，然后将其作为父模板：

    # Define nested stack that creates the lambda
    MyCustomLambdaToMakeMultiAzReplicas:
        Type: AWS::CloudFormation::Stack
        Properties:      
            TemplateURL: "<url to lambda template in s3>"
            TimeoutInMinutes: 1    

    # Define a custom resource using the lambda. Replica 
    # db instance id is passed to the lambda and the lambda is
    # executed       
    EnableMultiAzForReplica: 
        Type: "Custom::CustomLambdaToMakeMultiAzReplicas"
        Properties: 
            ServiceToken: !GetAtt MyCustomLambdaToMakeMultiAzReplicas.Outputs.LambdaArn
            DBinstanceId: !Ref ReadReplicaDbInstanceId

RDS只读副本-Cloudformation的多可用区

1 个答案: