Question

我在AWS网站上发现了一个很棒的文档，说明如何在第二个实例开始出现之前完成一个实例并进行配置。它位于https://aws.amazon.com/blogs/devops/tag/cloudformation/page/2/

该文档使用CreationPolicy属性和cfn-signal通知AWS Cloudformation Instance1已经出现。我试过了代码。它运行。但问题是Instance2首先出现而不是等待Instance1出现。这是代码，我在实例出现时附上了屏幕截图。

{
"AWSTemplateFormatVersion": "2010-09-09",
"Description": "EC2 Head Node Instance ",   
"Resources": {
    "EC2Instance1": {
        "Type": "AWS::EC2::Instance",
        "CreationPolicy" : {
            "ResourceSignal" : {
            "Timeout": "PT10M",
            "Count"  : "1"
            }
        },
        "Properties": {
            "ImageId": "ami-3723c04f",
            "UserData":{
                "Fn::Base64":{
                    "Fn::Join": ["", [
                                        "<script>\n",                                               
                                            "cfn-signal.exe -e 0 ",
                                            " --stack ", {"Ref" : "AWS::StackName"},
                                            " --resource EC2Instance1",
                                            " --region ", {"Ref" : "AWS::Region"}, "\n" ,                                           
                                        "</script>\n"

                                    ]

                    ]

                }


            },              
            "Tags" : [
                {"Key" : "Name", "Value" : "QRM Head Node"}            
            ]

        }
    },
    "EC2Instance2": {               
        "Type": "AWS::EC2::Instance",
        "Properties": {
            "ImageId": "ami-3723c04f",
             "Tags" : [{"Key" : "Dependency", "Value" : "EC2Instance1"}            
            ]

        }
    }


}

}

Answer 1

您必须指定DependsOn属性。

"EC2Instance2": {   
    "DependsOn": "EC2Instance1",            
    "Type": "AWS::EC2::Instance",
    "Properties": {
        "ImageId": "ami-3723c04f",
         "Tags" : [{"Key" : "Dependency", "Value" : "EC2Instance1"}            
        ]

    }
}

以上代码段应解决您的问题。

Edit-1 ：cfn-signal + DependsOn

创建一个cfn信号，以便在完成Ec2Instance1上的安装后发送信号。请参阅cfn-signal documentation。

现在，创建一个AWS::CloudFormation::WaitCondition并在Ec2Instance2中引用它。以下是有关如何在模板cfn-wait-condition中集成WaitConditions的文档。

Cloudformation“CreationPolicy”属性不起作用

1 个答案: