Amazon s3 使用CloudFormation在S3存储桶中创建Lambda通知

我试图在CloudFormation模板中为Lambda函数创建一个S3触发器。S3存储桶已经存在，并且正在创建Lambda函数

说不可能用CFT修改预先存在的基础设施（本例中是S3），但似乎说bucket必须是预先存在的

似乎无法使用CFT类型“AWS:：Lambda…”创建触发器，源服务需要创建触发器。在我的例子中，这是s3存储桶的NotificationConfiguration LambdaConfiguration。这些都对吗

当我试图用CFT将NotificationConfiguration添加到现有的S3存储桶时，它说我不能。有没有办法做到这一点

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不幸的是，官方的

AWS:：CloudFormation

模板只允许您作为父

AWS:：S3:：Bucket

资源的一部分进行控制，这意味着您不能将此配置附加到任何现有的Bucket，您必须将其应用到CloudFormation管理的Bucket才能工作

一种解决方法是使用JavaScript API调用将调用直接实现为一个函数。但是，由于修改S3 bucket上的NotificationConfiguration仅限于bucket的创建者，因此还需要添加一个资源，授予Lambda函数对

S3:PutBucketNotification

操作的访问权限

这是一个完整的、自包含的CloudFormation模板，演示了如何在将文件添加到现有S3存储桶时触发Lambda函数，使用2个Lambda支持的自定义资源（

BucketConfiguration

设置存储桶通知配置，

S3Object

将对象上载到存储桶）以及第三个Lambda函数（

BucketWatcher

，用于在对象上载到bucket时触发等待条件）

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我使用另一种解决方案，因为我个人不喜欢自定义资源。我创建一个云跟踪来捕获相关bucket的S3写事件，然后使用S3事件模式创建一个cloudwatch/eventbridge规则来触发Lambda函数。通过这种方式，我可以将Lambda函数挂接到一个现有的S3 bucket上，而不必触碰它，而且可以通过cloudformation轻松完成。

我相当确定，虽然bucket必须存在，但在创建模板之前它不必存在。在同一模板中创建通知配置和lambda函数旁边的bucket是否适合您的用例？如果是这样的话，这种方法将比修改现有基础设施更容易帮助您。无论哪种方式，都有一个解决方案，但其中一个要漂亮得多当你说“S3 bucket已经存在”时，你是否也在暗示该bucket是在CloudFormation之外创建的？使用CloudFormation在AWS中设置简单内容所需的代码数量之多令人难以置信使用CFN通用资源提供程序的类似解决方案（基本上是boto3代理）：

Description: Upload an object to an S3 bucket, triggering a Lambda event, returning the object key as a Stack Output.
Parameters:
  Key:
    Description: S3 Object key
    Type: String
    Default: test
  Body:
    Description: S3 Object body content
    Type: String
    Default: TEST CONTENT
  BucketName:
    Description: S3 Bucket name (must already exist)
    Type: String
Resources:
  BucketConfiguration:
    Type: Custom::S3BucketConfiguration
    DependsOn:
    - BucketPermission
    - NotificationBucketPolicy
    Properties:
      ServiceToken: !GetAtt S3BucketConfiguration.Arn
      Bucket: !Ref BucketName
      NotificationConfiguration:
        LambdaFunctionConfigurations:
        - Events: ['s3:ObjectCreated:*']
          LambdaFunctionArn: !GetAtt BucketWatcher.Arn
  S3BucketConfiguration:
    Type: AWS::Lambda::Function
    Properties:
      Description: S3 Object Custom Resource
      Handler: index.handler
      Role: !GetAtt LambdaExecutionRole.Arn
      Code:
        ZipFile: !Sub |
          var response = require('cfn-response');
          var AWS = require('aws-sdk');
          var s3 = new AWS.S3();
          exports.handler = function(event, context) {
            var respond = (e) => response.send(event, context, e ? response.FAILED : response.SUCCESS, e ? e : {});
            process.on('uncaughtException', e=>failed(e));
            var params = event.ResourceProperties;
            delete params.ServiceToken;
            if (event.RequestType === 'Delete') {
              params.NotificationConfiguration = {};
              s3.putBucketNotificationConfiguration(params).promise()
                .then((data)=>respond())
                .catch((e)=>respond());
            } else {
              s3.putBucketNotificationConfiguration(params).promise()
                .then((data)=>respond())
                .catch((e)=>respond(e));
            }
          };
      Timeout: 30
      Runtime: nodejs4.3
  BucketPermission:
    Type: AWS::Lambda::Permission
    Properties:
      Action: 'lambda:InvokeFunction'
      FunctionName: !Ref BucketWatcher
      Principal: s3.amazonaws.com
      SourceAccount: !Ref "AWS::AccountId"
      SourceArn: !Sub "arn:aws:s3:::${BucketName}"
  BucketWatcher:
    Type: AWS::Lambda::Function
    Properties:
      Description: Sends a Wait Condition signal to Handle when invoked
      Handler: index.handler
      Role: !GetAtt LambdaExecutionRole.Arn
      Code:
        ZipFile: !Sub |
          exports.handler = function(event, context) {
            console.log("Request received:\n", JSON.stringify(event));
            var responseBody = JSON.stringify({
              "Status" : "SUCCESS",
              "UniqueId" : "Key",
              "Data" : event.Records[0].s3.object.key,
              "Reason" : ""
            });
            var https = require("https");
            var url = require("url");
            var parsedUrl = url.parse('${Handle}');
            var options = {
                hostname: parsedUrl.hostname,
                port: 443,
                path: parsedUrl.path,
                method: "PUT",
                headers: {
                    "content-type": "",
                    "content-length": responseBody.length
                }
            };
            var request = https.request(options, function(response) {
                console.log("Status code: " + response.statusCode);
                console.log("Status message: " + response.statusMessage);
                context.done();
            });
            request.on("error", function(error) {
                console.log("send(..) failed executing https.request(..): " + error);
                context.done();
            });
            request.write(responseBody);
            request.end();
          };
      Timeout: 30
      Runtime: nodejs4.3
  Handle:
    Type: AWS::CloudFormation::WaitConditionHandle
  Wait:
    Type: AWS::CloudFormation::WaitCondition
    Properties:
      Handle: !Ref Handle
      Timeout: 300
  S3Object:
    Type: Custom::S3Object
    DependsOn: BucketConfiguration
    Properties:
      ServiceToken: !GetAtt S3ObjectFunction.Arn
      Bucket: !Ref BucketName
      Key: !Ref Key
      Body: !Ref Body
  S3ObjectFunction:
    Type: AWS::Lambda::Function
    Properties:
      Description: S3 Object Custom Resource
      Handler: index.handler
      Role: !GetAtt LambdaExecutionRole.Arn
      Code:
        ZipFile: !Sub |
          var response = require('cfn-response');
          var AWS = require('aws-sdk');
          var s3 = new AWS.S3();
          exports.handler = function(event, context) {
            var respond = (e) => response.send(event, context, e ? response.FAILED : response.SUCCESS, e ? e : {});
            var params = event.ResourceProperties;
            delete params.ServiceToken;
            if (event.RequestType == 'Create' || event.RequestType == 'Update') {
              s3.putObject(params).promise()
                .then((data)=>respond())
                .catch((e)=>respond(e));
            } else if (event.RequestType == 'Delete') {
              delete params.Body;
              s3.deleteObject(params).promise()
                .then((data)=>respond())
                .catch((e)=>respond(e));
            } else {
              respond({Error: 'Invalid request type'});
            }
          };
      Timeout: 30
      Runtime: nodejs4.3
  LambdaExecutionRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
        - Effect: Allow
          Principal: {Service: [lambda.amazonaws.com]}
          Action: ['sts:AssumeRole']
      Path: /
      ManagedPolicyArns:
      - "arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole"
      Policies:
      - PolicyName: S3Policy
        PolicyDocument:
          Version: '2012-10-17'
          Statement:
            - Effect: Allow
              Action:
                - 's3:PutObject'
                - 'S3:DeleteObject'
              Resource: !Sub "arn:aws:s3:::${BucketName}/${Key}"
  NotificationBucketPolicy:
    Type: AWS::S3::BucketPolicy
    Properties:
      Bucket: !Ref BucketName
      PolicyDocument:
        Statement:
          - Effect: "Allow"
            Action:
            - 's3:PutBucketNotification'
            Resource: !Sub "arn:aws:s3:::${BucketName}"
            Principal:
              AWS: !GetAtt LambdaExecutionRole.Arn
Outputs:
  Result:
    Value: !GetAtt Wait.Data