Day 47 : Integrating AWS SQS and SNS for Reliable Messaging

Welcome to Day 47. Today we will learn how to integrating AWS SQS and SNS for reliable messaging.

AWSTemplateFormatVersion: '2010-09-09'
Description: 'Nautilus DevOps Priority Queuing System'

Resources:
  HighPriorityQueue:
    Type: AWS::SQS::Queue
    Properties:
      QueueName: datacenter-High-Priority-Queue

  LowPriorityQueue:
    Type: AWS::SQS::Queue
    Properties:
      QueueName: datacenter-Low-Priority-Queue

  PriorityTopic:
    Type: AWS::SNS::Topic
    Properties:
      TopicName: datacenter-Priority-Queues-Topic

  HighPrioritySubscription:
    Type: AWS::SNS::Subscription
    Properties:
      TopicArn: !Ref PriorityTopic
      Endpoint: !GetAtt HighPriorityQueue.Arn
      Protocol: sqs
      FilterPolicy:
        priority:
          - high

  LowPrioritySubscription:
    Type: AWS::SNS::Subscription
    Properties:
      TopicArn: !Ref PriorityTopic
      Endpoint: !GetAtt LowPriorityQueue.Arn
      Protocol: sqs
      FilterPolicy:
        priority:
          - low

  LambdaExecutionRole:
    Type: AWS::IAM::Role
    Properties:
      RoleName: lambda_execution_role
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
          - Effect: Allow
            Principal:
              Service: lambda.amazonaws.com
            Action: sts:AssumeRole
      # Using Managed Policies to avoid PutRolePolicy permission errors in labs
      ManagedPolicyArns:
        - arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole
        - arn:aws:iam::aws:policy/AmazonSQSFullAccess

  PriorityLambdaFunction:
    Type: AWS::Lambda::Function
    Properties:
      FunctionName: datacenter-priorities-queue-function
      Handler: index.lambda_handler
      Role: !GetAtt LambdaExecutionRole.Arn
      Runtime: python3.9
      Timeout: 10
      Environment:
        Variables:
          high_priority_queue: !Ref HighPriorityQueue
          low_priority_queue: !Ref LowPriorityQueue
      Code:
        ZipFile: |
          import boto3
          import os
          sqs = boto3.client('sqs')
          def delete_message(queue_url, receipt_handle, message):
              response = sqs.delete_message(QueueUrl=queue_url, ReceiptHandle=receipt_handle)
              return "Message " + "'" + message + "'" + " deleted"
          def poll_messages(queue_url):
              response = sqs.receive_message(
                  QueueUrl=queue_url,
                  MaxNumberOfMessages=1,
                  MessageAttributeNames=['All'],
                  WaitTimeSeconds=3
              )
              if "Messages" in response:
                  receipt_handle=response['Messages'][0]['ReceiptHandle']
                  message = response['Messages'][0]['Body']
                  return delete_message(queue_url, receipt_handle, message)
              else:
                  return "No more messages to poll"
          def lambda_handler(event, context):
              response = poll_messages(os.environ['high_priority_queue'])
              if response == "No more messages to poll":
                  response = poll_messages(os.environ['low_priority_queue'])
              return response

  SqsQueuePolicy:
    Type: AWS::SQS::QueuePolicy
    Properties:
      Queues:
        - !Ref HighPriorityQueue
        - !Ref LowPriorityQueue
      PolicyDocument:
        Statement:
          - Effect: Allow
            Principal:
              Service: sns.amazonaws.com
            Action: sqs:SendMessage
            Resource: "*"
            Condition:
              ArnEquals:
                aws:SourceArn: !Ref PriorityTopic

aws cloudformation create-stack --stack-name datacenter-priority-stack --template-body file:///root/datacenter-priority-stack.yml --capabilities CAPABILITY_NAMED_IAM

Congratulations you did it. It looks good. This lab was successfully completed without any errors. See you in day 48. If you have any issues please let me know I will be happy to assist you. Stay tuned and learn together. If you find my article useful, please kindly like and share it.