# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
# SPDX-License-Identifier: MIT-0

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: Template to demonstrate maximum concurrency for Lambda function when using SQS queue as as event source. 

Globals:
  Function:
    Timeout: 15
    CodeUri: src/
    Runtime: python3.9

Resources:
  ReservedConcurrencyDeadLetterQueue:
    Type: AWS::SQS::Queue

  ReservedConcurrencyQueue:
    Type: AWS::SQS::Queue
    Properties:
      DelaySeconds: 0
      RedrivePolicy:
        deadLetterTargetArn : !GetAtt ReservedConcurrencyDeadLetterQueue.Arn
        maxReceiveCount : 1
      VisibilityTimeout: 20

  MaxConcurrencyDeadLetterQueue:
    Type: AWS::SQS::Queue

  MaxConcurrencyQueue:
    Type: AWS::SQS::Queue
    Properties:
      DelaySeconds: 0
      RedrivePolicy:
        deadLetterTargetArn : !GetAtt MaxConcurrencyDeadLetterQueue.Arn
        maxReceiveCount : 1
      VisibilityTimeout: 20

  MaxConcurrencyFunction:
    Type: AWS::Serverless::Function
    Properties:
      Handler: app.lambda_handler
      Events:
        SQSEventFromMax:
          Type: SQS
          Properties:
            Queue: !GetAtt MaxConcurrencyQueue.Arn
            BatchSize: 1
            Enabled: true
            ScalingConfig:
              MaximumConcurrency: 5

  ReservedConcurrencyFunction:
    Type: AWS::Serverless::Function
    Properties:
      ReservedConcurrentExecutions: 5
      Handler: app.lambda_handler
      Events:
        SQSEventFromReserved:
          Type: SQS
          Properties:
            Queue: !GetAtt ReservedConcurrencyQueue.Arn
            BatchSize: 1
            Enabled: true

  CloudWatchDashboard:
    Type: AWS::CloudWatch::Dashboard
    Properties: 
      DashboardName: Lambda-SQS-concurrency-monitoring
      DashboardBody: 
        !Sub 
          - |
            {
              "widgets": [
                  {
                      "height": 4,
                      "width": 16,
                      "y": 0,
                      "x": 0,
                      "type": "metric",
                      "properties": {
                          "metrics": [
                              [ "AWS/SQS", "ApproximateNumberOfMessagesVisible", "QueueName", "${MaxConcurrencyDeadLetterQueue}" ],
                              [ "...", "${ReservedConcurrencyDeadLetterQueue}" ]
                          ],
                          "sparkline": false,
                          "view": "singleValue",
                          "region": "${Region}",
                          "period": 900,
                          "stat": "Maximum",
                          "title": "Approximate number of messages visible in the DLQ"
                      }
                  },
                  {
                      "height": 7,
                      "width": 8,
                      "y": 8,
                      "x": 0,
                      "type": "metric",
                      "properties": {
                          "metrics": [
                              [ "AWS/Lambda", "ConcurrentExecutions", "FunctionName", "${MaxConcurrencyFunction}" ],
                              [ ".", "Throttles", ".", ".", { "color": "#d62728", "stat": "Sum" } ]
                          ],
                          "view": "timeSeries",
                          "stacked": false,
                          "region": "${Region}",
                          "period": 60,
                          "stat": "Maximum",
                          "title": "Max Concurrency Lambda Function"
                      }
                  },
                  {
                      "height": 7,
                      "width": 8,
                      "y": 8,
                      "x": 8,
                      "type": "metric",
                      "properties": {
                          "metrics": [
                              [ "AWS/Lambda", "ConcurrentExecutions", "FunctionName", "${ReservedConcurrencyFunction}", { "stat": "Maximum" } ],
                              [ ".", "Throttles", ".", ".", { "color": "#d62728" } ]
                          ],
                          "view": "timeSeries",
                          "stacked": false,
                          "region": "${Region}",
                          "title": "Reserved Concurrency Lambda Function",
                          "period": 60,
                          "stat": "Sum"
                      }
                  },
                  {
                      "type": "metric",
                      "x": 0,
                      "y": 4,
                      "width": 16,
                      "height": 4,
                      "properties": {
                          "metrics": [
                              [ "AWS/Lambda", "Invocations", "FunctionName", "${MaxConcurrencyFunction}", { "color": "#ff7f0e" } ],
                              [ "...", "${ReservedConcurrencyFunction}", { "color": "#2ca02c" } ]
                          ],
                          "sparkline": false,
                          "view": "singleValue",
                          "region": "${Region}",
                          "period": 900,
                          "stat": "Sum",
                          "title": "Total invocations in the last 15 minutes"
                      }
                  }
              ]
            }
          - 
            MaxConcurrencyDeadLetterQueue: !GetAtt MaxConcurrencyDeadLetterQueue.QueueName
            ReservedConcurrencyDeadLetterQueue: !GetAtt ReservedConcurrencyDeadLetterQueue.QueueName
            Region: !Ref AWS::Region
            MaxConcurrencyFunction: !Ref MaxConcurrencyFunction
            ReservedConcurrencyFunction: !Ref ReservedConcurrencyFunction

Outputs:
  MaxConcurrencyQueueURL:
    Description: URL of the SQS queue which sends messages to the Lambda function with the max concurrency configured as 5
    Value: !Ref MaxConcurrencyQueue

  ReservedConcurrencyQueueURL:
    Description: URL of the SQS Queue which sends messages to the Lambda function with max concurrency configured as 5
    Value: !Ref ReservedConcurrencyQueue
  DashboardURL:
    Description: Custom CloudWatch dashboard that highlight SQS and Lambda metrics relevant to maximum and reserved concurrency 
    Value: !Sub 
      - https://${Region}.console.aws.amazon.com/cloudwatch/home#dashboards:name=Lambda-SQS-concurrency-monitoring
      - Region: !Ref AWS::Region