如何使用Cloudformation解析AWS上的免费层RHEL AMI ID？
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我已经开始编写一些简单的Cloudformation脚本来配置基础架构。它正在唤醒4个节点（1个Ansible Headnode - 3个Slave）。所有节点映像都是AWS上的免费层RHEL映像。问题是RHEL映像的映像ID在AWS上一直在变化。因此，如果我想在下周因任何原因运行我的脚本，我必须编辑图像ID。还有一个选择是我可以设置脚本等待用户写入图像ID，但这不是我的解决方案。
有没有什么方法可以在AWS上动态解析免费层RHEL AMI的图像ID以进行云形成？
答案
TL; DR这个walkthrough提供您需要的所有信息：
我从参考文献中使用的方法是：
- 创建Lambda以查找与所需模式匹配的最新AMI。
- 在S3中存储Lambda的代码。
- 从CloudFormation中调用Lambda并使用从Lambda检索的信息来创建具有最新AMI的EC2实例。
这是来自参考的示例Lambda：
/**
* 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:
" + 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 + ":
", 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:
", 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...
");
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();
}
这是资源中的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": {
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