amazon-web-services - "Fn::Join"带有参数分隔符？

Question

我正在尝试参数化 Fn::Join 使用的分隔符，例如起初我有:

"Name" : { "Fn::Join" : [ ".", [ 
           { "Ref":"serviceName"}, { "Ref": "environment" } ] ] },

效果很好，但后来我将其更改为:

"Name" : { "Fn::Join" : [ {"Ref":"HostNameSeparator"}, [
           { "Ref":"serviceName"}, { "Ref": "environment" } ] ] },

我在验证阶段收到以下错误:

A client error (ValidationError) occurred when calling the
ValidateTemplate operation: Template error: every Fn::Join object
requires two parameters, (1) a string delimiter and (2) a list of
strings to be joined or a function that returns a list of strings
(such as Fn::GetAZs) to be joined.

是否可以执行我想要的操作，即将连接分隔符作为模板参数传递？

(为了清楚起见，我缩短了上面的示例，请忽略拼写错误)

Answer 1

您可以通过使用 CustomResource 来实现此目的。此 CloudFormation 模板已准备好运行，并说明了它的工作原理。分隔符作为参数传递，您将在堆栈的输出中找到连接的字符串。

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Description": "Example Join",
    "Parameters": {
        "Delimiter": {
            "Type": "String"
        }
    },
    "Resources": {
        "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": "root",
                        "PolicyDocument": {
                            "Version": "2012-10-17",
                            "Statement": [
                                {
                                    "Effect": "Allow",
                                    "Action": [
                                        "logs:CreateLogGroup",
                                        "logs:CreateLogStream",
                                        "logs:PutLogEvents"
                                    ],
                                    "Resource": "arn:aws:logs:*:*:*"
                                },
                                {
                                    "Effect": "Allow",
                                    "Action": [
                                        "cloudformation:DescribeStacks"
                                    ],
                                    "Resource": "*"
                                }
                            ]
                        }
                    }
                ]
            }
        },
        "LambdaJoin": {
            "Type": "AWS::Lambda::Function",
            "Properties": {
                "Code": {
                    "ZipFile":  { "Fn::Join": ["\n", [
                        "var response = require('cfn-response');\n",
                        "exports.handler = function (event, context) {\n",
                        "if (event.RequestType === 'Delete') {\n",
                        "return response.send(event, context, response.SUCCESS, {}, event.PhysicalResourceId);\n",
                        "}\n",
                        "var delimiter = event.ResourceProperties.delimiter || '';\n",
                        "var strings = event.ResourceProperties.strings || [];\n",
                        "return response.send(event, context, response.SUCCESS, { string: strings.join(delimiter) }, event.PhysicalResourceId);\n",
                        "};\n"
                    ]]}
                },
                "Handler": "index.handler",
                "Runtime": "nodejs",
                "Timeout": "10",
                "Role": { "Fn::GetAtt" : ["LambdaExecutionRole", "Arn"] }
            }
        },
        "CustomJoin": {
            "Type": "Custom::Join",
            "Version": "1.0",
            "Properties": {
                "ServiceToken": { "Fn::GetAtt": ["LambdaJoin", "Arn"] },
                "delimiter": { "Ref": "Delimiter" },
                "strings": ["first", "second", "third"]
            },
            "DependsOn": ["LambdaJoin"]
        }
    },
    "Outputs": {
        "JoinedString": {
            "Value": { "Fn::GetAtt": ["CustomJoin", "string"] }
        }
    }
}