如何从 CloudFormation 中的 Elastic Beanstalk 环境中提取负载均衡器名称

我使用以下代码片段在 CloudFormation 中创建了 Elastic Beanstalk 和 CloudWatch 警报：

        "ElasticBeanstalkEnvironment": {
        "Type": "AWS::ElasticBeanstalk::Environment",
        "Properties": {
            "ApplicationName": "my-app",
            "EnvironmentName": "my-eb",
            "SolutionStackName": "64bit Amazon Linux 2018.03 v3.0.1 running Tomcat 8 Java 8",
            "OptionSettings": [
                {
                    "Namespace": "aws:elb:loadbalancer",
                    "OptionName": "CrossZone",
                    "Value": "true"
                },
                {
                    "Namespace": "aws:elb:listener:80",
                    "OptionName": "ListenerProtocol",
                    "Value": "HTTP"
                },
                {
                    "Namespace": "aws:elb:listener:80",
                    "OptionName": "InstancePort",
                    "Value": "80"
                },
                etc...
            ]
        },
        "CloudWatchBacken500XXAlarm": {
            "Type": "AWS::CloudWatch::Alarm",
            "Properties" : {
                "AlarmActions": ["arn:aws:sns:us-east-1:12345678:mysnstopic"],
                "Namespace": "AWS/ELB",
                "Dimensions": [{
                    "Name": "LoadBalancerName",
                    "Value" : {
                        "Fn::GetAtt": [
                            "ElasticBeanstalkEnvironment",
                            "EndpointURL"  
                        ]
                    }
                  }],
                "MetricName": "HTTPCode_Backend_5XX",
                "Statistic": "Sum",
                "Period": "60",
                "EvaluationPeriods": "1",
                "ComparisonOperator": "GreaterThanOrEqualToThreshold",
                "Threshold": "1"
                }
        }

您可以看到 CloudWatch 警报配置为在 Elastic Beanstalk 的负载均衡器收到 5XX 错误时发出警报。但是，我无法获取负载均衡器名称属性，该属性如下所示：

awseb-e-a-AWSEBLoa-AY8LC6V30OAW

相反，Fn::GetAtt("EndpointURL") 属性返回负载均衡器的 DNSName，如下所示：

awseb-e-a-AWSEBLoa-AY8LC6V30OAW-175133046.us-east-1.elb.amazonaws.com

这将无法正确创建 CloudWatch 警报，因为它期望获取负载均衡器名称而不是 DNSName。

获取负载均衡器名称的最佳方式是什么？我不想将负载均衡器创建为外部资源，例如“AWS::ElasticLoadBalancing::LoadBalancer”，或者尝试使用某些子字符串方法从 DNSName 字符串中提取名称字符串。

好的，我找到了一个解决方案，它非常破解，我已经能够对从 - Fn::GetAtt("EndpointURL") 返回的 DNSName 字符串进行多次 Split/Select/Join 调用，从端点提取 LoadBalancerName。这是代码：

"CloudWatchBackend500XXAlarm": {
"Type": "AWS::CloudWatch::Alarm",
"Properties" : {
    "AlarmDescription": "Elastic Beanstalk Has Received 5XX Backend Connection Errors",
    "AlarmActions": ["arn:aws:sns:us-east-1:1234567890:mysnstopic"],
    "Namespace": "AWS/ELB",
    "Dimensions": [
        {
            "Name": "LoadBalancerName",
            "Value": {
                "Fn::Join": ["", [{
                    "Fn::Select": [
                        "0",
                        {
                            "Fn::Split": ["AWSEBLoa-",
                                {
                                    "Fn::GetAtt": [
                                        "ElasticBeanstalkEnvironment",
                                        "EndpointURL"
                                    ]
                                }
                            ]
                        }
                    ]
                },
                "AWSEBLoa-",
                {
                    "Fn::Select": [
                        "0",
                        {
                            "Fn::Split": ["-",
                                {
                                    "Fn::Select": [
                                        "1",
                                        {
                                            "Fn::Split": ["AWSEBLoa-",
                                                {
                                                    "Fn::GetAtt": [
                                                        "ElasticBeanstalkEnvironment",
                                                        "EndpointURL"
                                                    ]
                                                }
                                            ]
                                        }
                                    ]
                                }
                            ]
                        }
                    ]
                }
            ]]
        }
        }
    ],                  
    "MetricName": "HTTPCode_Backend_5XX",
    "Statistic": "Sum",
    "Period": "60",
    "EvaluationPeriods": "1",
    "ComparisonOperator": "GreaterThanOrEqualToThreshold",
    "Threshold": "1"
}

}

即上面的代码能够从“awseb-k-3-AWSEBLoa-11B26NY4PQB9A-739614614.us-east-1.elb.amazonaws.com”中提取“awseb-k-3-AWSEBLoa-11B26NY4PQB9A”，并且 CloudWatch 警报正常工作完美。我想我必须调整代码才能与内部负载均衡器一起使用，即在 DNSName 开头使用“internal-”进行格式化，但我现在没问题。

我已向 AWS 提交请求，要求他们添加 CloudFormation 方法以返回 LoadBalancer 名称，而不仅仅是 DNSName。