how to pass bucket/key name to fargate job via a cloudwatch event trigger on s3 object creation event? - aws-cloudformation

Question

I have create a fargate task and trying to trigger it via s3 object creation event ( see sample below) via cloudformation.as it cannot trigger it directly, i have created a cloudwatchevent. I am trying to pass the bucket and obj name to my fargate task code . doing some research, i came across -> InputTransformer, but i'm not sure how to pass the value of my bucket and key name and how to read it in my python code. any help will be appreciated.
AWSTemplateFormatVersion: 2010-09-09
Description: An example CloudFormation template for Fargate.
Parameters:
VPC:
Type: AWS::EC2::VPC::Id
SubnetA:
Type: AWS::EC2::Subnet::Id
SubnetB:
Type: AWS::EC2::Subnet::Id
Image:
Type: String
Default: 123456789012.dkr.ecr.region.amazonaws.com/image:tag
Resources:
mybucket:
Properties:
BucketName: 'mytestbucket-us'
cloudwatchEvent:
Type: AWS::Events::Rule
Properties:
EventPattern:
source:
- aws.s3
detail:
eventSource:
- s3.amazonaws.com
eventName:
- PutObject
- CompleteMultipartUpload
requestParameters:
bucketName:
- !Ref mybucket
Targets:
- Id: my-fargate-task
Arn: myclusterArn
RoleArn: myinvocationrolearn
Input:
'Fn::Sub':
- >-
{"containerOverrides": [{"name":"somecontainer"]}
EcsParameters:
TaskDefinition:
LaunchType: 'FARGATE'
...
NetworkConfiguration:
...
Cluster:
Type: AWS::ECS::Cluster
Properties:
ClusterName: !Join ['', [!Ref ServiceName, Cluster]]
TaskDefinition:
Type: AWS::ECS::TaskDefinition
DependsOn: LogGroup
Properties:
Family: !Join ['', [!Ref ServiceName, TaskDefinition]]
NetworkMode: awsvpc
RequiresCompatibilities:
- FARGATE
Cpu: 256
Memory: 2GB
ExecutionRoleArn: !Ref ExecutionRole
TaskRoleArn: !Ref TaskRole
ContainerDefinitions:
- Name: !Ref ServiceName
Image: !Ref Image
# A role needed by ECS
ExecutionRole:
Type: AWS::IAM::Role
Properties:
RoleName: !Join ['', [!Ref ServiceName, ExecutionRole]]
AssumeRolePolicyDocument:
Statement:
- Effect: Allow
Principal:
Service: ecs-tasks.amazonaws.com
Action: 'sts:AssumeRole'
ManagedPolicyArns:
- 'arn:aws:iam::aws:policy/service-role/AmazonECSTaskExecutionRolePolicy'
# A role for the containers
TaskRole:
Type: AWS::IAM::Role
Properties:
RoleName: !Join ['', [!Ref ServiceName, TaskRole]]
AssumeRolePolicyDocument:
Statement:
- Effect: Allow
Principal:
Service: ecs-tasks.amazonaws.com
Action: 'sts:AssumeRole'

Answer 1

You would use a CloudWatch Event Input Transformer to extract the data you need from the event, and pass that data to the ECS task as environment variable(s) in the target's ContainerOverrides. I don't use CloudFormation, but here's an example using Terraform.

Answer 2

You can't. CloudWatch events do not pass data to ECS jobs. You need to develop your own mechanism for that. For example, trigger lambda first, store event in S3 Parameter Store or DynamoDB, and then invoke your ECS job which will get stored data.