example.template.json

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Description": "Lambda DynamoDB Stream Triggers",
  "Parameters": {
    "DynamoDBStreamCustomResourceLambdaName": {
      "Type": "String",
      "Default": "cfn-dynamodb-streamspecification-0-1-1",
      "Description": "The name of the DynamoDB Stream Custom Resource Lambda you deployed to test this stack."
    },
    "StreamViewType": {
      "Type": "String",
      "Description": "The record change ViewType type to send to the Lambda logging DynamoDB events.",
      "AllowedValues": [
        "NEW_IMAGE",
        "OLD_IMAGE",
        "NEW_AND_OLD_IMAGES",
        "KEYS_ONLY"
      ],
      "Default": "NEW_IMAGE"
    },
    "MyTableToUse": {
      "Type": "String",
      "AllowedValues": [
        "Alpha",
        "Beta"
      ],
      "Default": "Alpha",
      "Description": "Toggle this to demo swapping which table a StreamSpecification works off of."
    }
  },
  "Conditions": {
    "UsingAlphaTable": {
      "Fn::Equals": [
        "Alpha",
        {
          "Ref": "MyTableToUse"
        }
      ]
    }
  },
  "Resources": {
    "MyDynamoDBTableAlpha": {
      "Type": "AWS::DynamoDB::Table",
      "Properties": {
        "AttributeDefinitions": [
          {
            "AttributeName": "id",
            "AttributeType": "S"
          }
        ],
        "KeySchema": [
          {
            "AttributeName": "id",
            "KeyType": "HASH"
          }
        ],
        "ProvisionedThroughput": {
          "ReadCapacityUnits": 10,
          "WriteCapacityUnits": 10
        }
      }
    },
    "MyDynamoDBTableBeta": {
      "Type": "AWS::DynamoDB::Table",
      "Properties": {
        "AttributeDefinitions": [
          {
            "AttributeName": "id",
            "AttributeType": "S"
          }
        ],
        "KeySchema": [
          {
            "AttributeName": "id",
            "KeyType": "HASH"
          }
        ],
        "ProvisionedThroughput": {
          "ReadCapacityUnits": 10,
          "WriteCapacityUnits": 10
        }
      }
    },
    "MyDynamoDBStreamSpecification": {
      "Type": "Custom::DynamoDBStreamSpecification",
      "DependsOn": [
        "MyDynamoDBTableAlpha",
        "MyDynamoDBTableBeta"
      ],
      "Properties": {
        "ServiceToken": {
          "Fn::Join": [
            ":",
            [
              "arn",
              "aws",
              "lambda",
              {
                "Ref": "AWS::Region"
              },
              {
                "Ref": "AWS::AccountId"
              },
              "function",
              {
                "Ref": "DynamoDBStreamCustomResourceLambdaName"
              }
            ]
          ]
        },
        "TableName": {
          "Fn::If": [
            "UsingAlphaTable",
            {
              "Ref": "MyDynamoDBTableAlpha"
            },
            {
              "Ref": "MyDynamoDBTableBeta"
            }
          ]
        },
        "StreamViewType": {
          "Ref": "StreamViewType"
        }
      }
    },
    "MyLambdaDynamoDBTrigger": {
      "Type": "AWS::Lambda::Function",
      "DependsOn": [
        "LambdaExecutionRole",
        "LambdaExecutionPolicy"
      ],
      "Properties": {
        "Handler": "index.handler",
        "Role": {
          "Fn::GetAtt": [
            "LambdaExecutionRole",
            "Arn"
          ]
        },
        "Code": {
          "ZipFile": {
            "Fn::Join": [
              "\n",
              [
                "// Demonstrate the Lambda sees DynamoDB Table updates",
                "console.log('Loading function');",
                "exports.handler = function(event, context) {",
                "  console.log('Received event: %j',event);",
                "  event.Records.forEach(function(record) {",
                "    console.log(record.eventID);",
                "    console.log(record.eventName);",
                "    console.log('DynamoDB Record: %j',record.dynamodb);",
                "  });",
                "  console.log('Processed %s records!', event.Records.length);",
                "  context.done();",
                "};",
                ""
              ]
            ]
          }
        },
        "Runtime": "nodejs",
        "Timeout": 10
      }
    },
    "MyLambdaEventSourceMapping":{
      "Type": "AWS::Lambda::EventSourceMapping",
      "DependsOn": [
        "MyDynamoDBStreamSpecification",
        "MyLambdaDynamoDBTrigger",
        "LambdaExecutionPolicy",
        "LambdaExecutionRole"
      ],
      "Properties": {
        "BatchSize": 100,
        "Enabled": true,
        "EventSourceArn": {
          "Fn::GetAtt": [
            "MyDynamoDBStreamSpecification",
            "Arn"
          ]
        },
        "FunctionName": {
          "Ref": "MyLambdaDynamoDBTrigger"
        },
        "StartingPosition": "TRIM_HORIZON"
      }
    },
    "LambdaExecutionPolicy": {
      "DependsOn": [
        "MyDynamoDBStreamSpecification",
        "MyDynamoDBTableAlpha",
        "MyDynamoDBTableBeta",
        "LambdaExecutionRole"
      ],
      "Type": "AWS::IAM::Policy",
      "Properties": {
        "PolicyName": "MyLambdaDynamoDBTriggerRolePolicy",
        "Roles": [
          {
            "Ref": "LambdaExecutionRole"
          }
        ],
        "PolicyDocument": {
          "Version": "2012-10-17",
          "Statement": [
            {
              "Effect": "Allow",
              "Action": [
                "lambda:InvokeFunction"
              ],
              "Resource": [
                "*"
              ]
            },
            {
              "Effect": "Allow",
              "Action": [
                "dynamodb:GetRecords",
                "dynamodb:GetShardIterator",
                "dynamodb:DescribeStream",
                "dynamodb:ListStreams",
                "logs:CreateLogGroup",
                "logs:CreateLogStream",
                "logs:PutLogEvents"
              ],
              "Resource": [
                "*"
              ]
            }
          ]
        }
      }
    },
    "LambdaExecutionRole": {
      "Type": "AWS::IAM::Role",
      "Properties": {
        "AssumeRolePolicyDocument": {
          "Version": "2012-10-17",
          "Statement": [
            {
              "Effect": "Allow",
              "Principal": {
                "Service": [
                  "lambda.amazonaws.com"
                ]
              },
              "Action": [
                "sts:AssumeRole"
              ]
            }
          ]
        },
        "Path": "/"
      }
    }
  },
  "Outputs": {
    "ConsoleLinkForTableCreated": {
      "Description": "Click this link, go to the Items subtab, hit Create Item, make an item, then click the other Output link to see the demo stack working.",
      "Value": {
        "Fn::Join": [
          "",
          [
            "https://console.aws.amazon.com/dynamodb/home?region=",
            {
              "Ref": "AWS::Region"
            },
            "#tables:selected=",
            {
              "Fn::If": [
                "UsingAlphaTable",
                {
                  "Ref": "MyDynamoDBTableAlpha"
                },
                {
                  "Ref": "MyDynamoDBTableBeta"
                }
              ]
            }
          ]
        ]
      }
    },
    "ConsoleLinkForTriggerLambdaLogStream": {
      "Description": "Follow the link to see trigger logging working!",
      "Value": {
        "Fn::Join": [
          "",
          [
            "https://console.aws.amazon.com/cloudwatch/home?region=",
            {
              "Ref": "AWS::Region"
            },
            "#logStream:group=/aws/lambda/",
            {
              "Ref": "MyLambdaDynamoDBTrigger"
            },
            ";"
          ]
        ]
      }
    }
  }
}