amazon-web-services - 如何使用 Cloudformation 解析 AWS 上的免费套餐 RHEL AMI ID？

Question

我已经开始编写一些简单的 Cloudformation 脚本来配置基​​础设施。它正在唤醒 4 个节点(1 个 Ansible 头节点 - 3 个从节点)。所有节点镜像都是 AWS 上的免费 RHEL 镜像。问题是 RHEL 镜像的镜像 ID 在 AWS 上一直在变化。因此，如果我出于任何原因想在下周运行我的脚本，我必须编辑图像 ID。另一种选择是我可以将脚本设置为等待用户写入图像 ID，但这对我来说不是一个解决方案。

有什么方法可以在 AWS 上动态解析免费版 RHEL AMI 的镜像 ID 以进行云信息形成吗？

Answer 1

TL;DR 这个 walkthrough提供您需要的所有信息:

我从引用文献中使用的方法是:

1. 创建 Lambda 以查找与您所需模式匹配的最新 AMI。
2. 将 Lambda 代码存储在 S3 中。
3. 从 CloudFormation 中调用该 Lambda，并使用从 Lambda 检索到的信息来创建具有最新 AMI 的 EC2 实例。

这是引用文献中的 Lambda 示例:

/**
* A sample Lambda function that looks up the latest AMI ID for a given region and architecture.
**/

// Map instance architectures to an AMI name pattern
var archToAMINamePattern = {
    "PV64": "amzn-ami-pv*x86_64-ebs",
    "HVM64": "amzn-ami-hvm*x86_64-gp2",
    "HVMG2": "amzn-ami-graphics-hvm*x86_64-ebs*"
};
var aws = require("aws-sdk");

exports.handler = function(event, context) {

    console.log("REQUEST RECEIVED:\n" + JSON.stringify(event));

    // For Delete requests, immediately send a SUCCESS response.
    if (event.RequestType == "Delete") {
        sendResponse(event, context, "SUCCESS");
        return;
    }

    var responseStatus = "FAILED";
    var responseData = {};

    var ec2 = new aws.EC2({region: event.ResourceProperties.Region});
    var describeImagesParams = {
        Filters: [{ Name: "name", Values: [archToAMINamePattern[event.ResourceProperties.Architecture]]}],
        Owners: [event.ResourceProperties.Architecture == "HVMG2" ? "679593333241" : "amazon"]
    };

    // Get AMI IDs with the specified name pattern and owner
    ec2.describeImages(describeImagesParams, function(err, describeImagesResult) {
        if (err) {
            responseData = {Error: "DescribeImages call failed"};
            console.log(responseData.Error + ":\n", err);
        }
        else {
            var images = describeImagesResult.Images;
            // Sort images by name in decscending order. The names contain the AMI version, formatted as YYYY.MM.Ver.
            images.sort(function(x, y) { return y.Name.localeCompare(x.Name); });
            for (var j = 0; j < images.length; j++) {
                if (isBeta(images[j].Name)) continue;
                responseStatus = "SUCCESS";
                responseData["Id"] = images[j].ImageId;
                break;
            }
        }
        sendResponse(event, context, responseStatus, responseData);
    });
};

// Check if the image is a beta or rc image. The Lambda function won't return any of those images.
function isBeta(imageName) {
    return imageName.toLowerCase().indexOf("beta") > -1 || imageName.toLowerCase().indexOf(".rc") > -1;
}


// Send response to the pre-signed S3 URL 
function sendResponse(event, context, responseStatus, responseData) {

    var responseBody = JSON.stringify({
        Status: responseStatus,
        Reason: "See the details in CloudWatch Log Stream: " + context.logStreamName,
        PhysicalResourceId: context.logStreamName,
        StackId: event.StackId,
        RequestId: event.RequestId,
        LogicalResourceId: event.LogicalResourceId,
        Data: responseData
    });

    console.log("RESPONSE BODY:\n", responseBody);

    var https = require("https");
    var url = require("url");

    var parsedUrl = url.parse(event.ResponseURL);
    var options = {
        hostname: parsedUrl.hostname,
        port: 443,
        path: parsedUrl.path,
        method: "PUT",
        headers: {
            "content-type": "",
            "content-length": responseBody.length
        }
    };

    console.log("SENDING RESPONSE...\n");

    var request = https.request(options, function(response) {
        console.log("STATUS: " + response.statusCode);
        console.log("HEADERS: " + JSON.stringify(response.headers));
        // Tell AWS Lambda that the function execution is done  
        context.done();
    });

    request.on("error", function(error) {
        console.log("sendResponse Error:" + error);
        // Tell AWS Lambda that the function execution is done  
        context.done();
    });

    // write data to request body
    request.write(responseBody);
    request.end();
}

这是来自资源的 CloudFormation 模板:

{
  "AWSTemplateFormatVersion" : "2010-09-09",

  "Description" : "AWS CloudFormation AMI Look Up Sample Template: Demonstrates how to dynamically specify an AMI ID. This template provisions an EC2 instance with an AMI ID that is based on the instance's type and region. **WARNING** This template creates an Amazon EC2 instance. You will be billed for the AWS resources used if you create a stack from this template.",

  "Parameters": {
    "InstanceType" : {
      "Description" : "EC2 instance type",
      "Type" : "String",
      "Default" : "m1.small",
      "AllowedValues" : [ "t1.micro", "t2.micro", "t2.small", "t2.medium", "m1.small", "m1.medium", "m1.large", "m1.xlarge", "m2.xlarge", "m2.2xlarge", "m2.4xlarge", "m3.medium", "m3.large", "m3.xlarge", "m3.2xlarge", "c1.medium", "c1.xlarge", "c3.large", "c3.xlarge", "c3.2xlarge", "c3.4xlarge", "c3.8xlarge", "c4.large", "c4.xlarge", "c4.2xlarge", "c4.4xlarge", "c4.8xlarge", "g2.2xlarge", "r3.large", "r3.xlarge", "r3.2xlarge", "r3.4xlarge", "r3.8xlarge", "i2.xlarge", "i2.2xlarge", "i2.4xlarge", "i2.8xlarge", "d2.xlarge", "d2.2xlarge", "d2.4xlarge", "d2.8xlarge", "hi1.4xlarge", "hs1.8xlarge", "cr1.8xlarge", "cc2.8xlarge", "cg1.4xlarge"],
      "ConstraintDescription" : "Must be a valid EC2 instance type."
    },
    "ModuleName" : {
      "Description" : "The name of the JavaScript file",
      "Type" : "String",
      "Default" : "amilookup"
    },
    "S3Bucket" : {
      "Description" : "The name of the bucket that contains your packaged source",
      "Type" : "String"
    },
    "S3Key" : {
      "Description" : "The name of the ZIP package",
      "Type" : "String",
      "Default" : "amilookup.zip"
    }
  },

  "Mappings" : {
    "AWSInstanceType2Arch" : {
      "t1.micro"    : { "Arch" : "PV64"   },
      "t2.micro"    : { "Arch" : "HVM64"  },
      "t2.small"    : { "Arch" : "HVM64"  },
      "t2.medium"   : { "Arch" : "HVM64"  },
      "m1.small"    : { "Arch" : "PV64"   },
      "m1.medium"   : { "Arch" : "PV64"   },
      "m1.large"    : { "Arch" : "PV64"   },
      "m1.xlarge"   : { "Arch" : "PV64"   },
      "m2.xlarge"   : { "Arch" : "PV64"   },
      "m2.2xlarge"  : { "Arch" : "PV64"   },
      "m2.4xlarge"  : { "Arch" : "PV64"   },
      "m3.medium"   : { "Arch" : "HVM64"  },
      "m3.large"    : { "Arch" : "HVM64"  },
      "m3.xlarge"   : { "Arch" : "HVM64"  },
      "m3.2xlarge"  : { "Arch" : "HVM64"  },
      "c1.medium"   : { "Arch" : "PV64"   },
      "c1.xlarge"   : { "Arch" : "PV64"   },
      "c3.large"    : { "Arch" : "HVM64"  },
      "c3.xlarge"   : { "Arch" : "HVM64"  },
      "c3.2xlarge"  : { "Arch" : "HVM64"  },
      "c3.4xlarge"  : { "Arch" : "HVM64"  },
      "c3.8xlarge"  : { "Arch" : "HVM64"  },
      "c4.large"    : { "Arch" : "HVM64"  },
      "c4.xlarge"   : { "Arch" : "HVM64"  },
      "c4.2xlarge"  : { "Arch" : "HVM64"  },
      "c4.4xlarge"  : { "Arch" : "HVM64"  },
      "c4.8xlarge"  : { "Arch" : "HVM64"  },
      "g2.2xlarge"  : { "Arch" : "HVMG2"  },
      "r3.large"    : { "Arch" : "HVM64"  },
      "r3.xlarge"   : { "Arch" : "HVM64"  },
      "r3.2xlarge"  : { "Arch" : "HVM64"  },
      "r3.4xlarge"  : { "Arch" : "HVM64"  },
      "r3.8xlarge"  : { "Arch" : "HVM64"  },
      "i2.xlarge"   : { "Arch" : "HVM64"  },
      "i2.2xlarge"  : { "Arch" : "HVM64"  },
      "i2.4xlarge"  : { "Arch" : "HVM64"  },
      "i2.8xlarge"  : { "Arch" : "HVM64"  },
      "d2.xlarge"   : { "Arch" : "HVM64"  },
      "d2.2xlarge"  : { "Arch" : "HVM64"  },
      "d2.4xlarge"  : { "Arch" : "HVM64"  },
      "d2.8xlarge"  : { "Arch" : "HVM64"  },
      "hi1.4xlarge" : { "Arch" : "HVM64"  },
      "hs1.8xlarge" : { "Arch" : "HVM64"  },
      "cr1.8xlarge" : { "Arch" : "HVM64"  },
      "cc2.8xlarge" : { "Arch" : "HVM64"  }
    }
  },

  "Resources" : {
    "SampleInstance": {  
      "Type": "AWS::EC2::Instance",
      "Properties": {
        "InstanceType"   : { "Ref" : "InstanceType" },
        "ImageId": { "Fn::GetAtt": [ "AMIInfo", "Id" ] }
      }
    },

    "AMIInfo": {
      "Type": "Custom::AMIInfo",
      "Properties": {
        "ServiceToken": { "Fn::GetAtt" : ["AMIInfoFunction", "Arn"] },
        "Region": { "Ref": "AWS::Region" },
        "Architecture": { "Fn::FindInMap" : [ "AWSInstanceType2Arch", { "Ref" : "InstanceType" }, "Arch" ] }
      }
    },

    "AMIInfoFunction": {
      "Type": "AWS::Lambda::Function",
      "Properties": {
        "Code": {
            "S3Bucket": { "Ref": "S3Bucket" },
            "S3Key": { "Ref": "S3Key" }
        },
        "Handler": { "Fn::Join" : [ "", [{ "Ref": "ModuleName" },".handler"] ] },
        "Role": { "Fn::GetAtt" : ["LambdaExecutionRole", "Arn"] },        
        "Runtime": "nodejs4.3",
        "Timeout": "30"
      }
    },

    "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": ["ec2:DescribeImages"],
                "Resource": "*"
            }]
          }
        }]
      }
    }    
  },

  "Outputs" : {
    "AMIID" : {
      "Description": "The Amazon EC2 instance AMI ID.",
      "Value" : { "Fn::GetAtt": [ "AMIInfo", "Id" ] }
    }
  }  
}

引用

https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/walkthrough-custom-resources-lambda-lookup-amiids.html