只有当消息计数达到SQS中的目标值时，我才能触发lambda吗？

Question

我正在编写AWS来读取来自SQS的消息，然后在过滤后将一些消息保存到S3中。由于80%的消息将被过滤掉，所以我决定为100000条SQS消息编写一次S3。

只有在SQS中的消息达到10000时才有可能触发Lambda吗？

Answer 1

在AWS CloudWatch的帮助下这是可能的。

您可以配置一个AWS CloudWatch警报，一旦您的AlarmAction队列获得100000条可见消息，它就会触发一个"AlarmAction“。如果发生“警报”，您将通知SNS主题，然后触发AWS Lambda。

如果您使用的是AWS CloudFormation，它可能如下所示：

AWSTemplateFormatVersion: 2010-09-09
Resources:
  Queue:
    Type: AWS::SQS::Queue

  QueueVisibleMessagesTopic:
    Type: AWS::SNS::Topic

  LambdaExecutionRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Version: 2012-10-17
        Statement:
          - Effect: Allow
            Principal:
              Service: lambda.amazonaws.com
            Action: sts:AssumeRole
      ManagedPolicyArns:
        - arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole

  Lambda:
    Type: AWS::Lambda::Function
    Properties:
      Handler: handler.index
      Role: !GetAtt LambdaExecutionRole.Arn
      Runtime: nodejs8.10
      MemorySize: 128
      Timeout: 10

  LambdaSubscription:
    Type: AWS::SNS::Subscription
    Properties:
      Endpoint: !GetAtt Lambda.Arn
      Protocol: lambda
      TopicArn: !Ref QueueVisibleMessagesTopic

  LambdaSubscriptionPermissions:
    Type: AWS::Lambda::Permission
    Properties:
      FunctionName: !GetAtt Lambda.Arn
      Action: lambda:InvokeFunction
      Principal: sns.amazonaws.com
      SourceArn: !Ref QueueVisibleMessagesTopic

  QueueVisibleMessagesAlarm:
    Type: AWS::CloudWatch::Alarm
    Properties:
      Namespace: AWS/SQS
      MetricName: ApproximateNumberOfMessagesVisible
      Dimensions:
        - Name: QueueName
          Value: !GetAtt Queue.QueueName
      Statistic: Sum
      Period: 300
      EvaluationPeriods: 1
      ComparisonOperator: GreaterThanOrEqualToThreshold
      Threshold: 100000
      AlarmActions:
        - !Ref QueueVisibleMessagesTopic