Question 18669 in Amazon Web Sevices Question posted in
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How do I trigger a Lambda from an S3 bucket ObjectCreated event for different cased file suffixes? – Amazon Web Sevices

I’m trying to trigger a Lambda when a new file is uploaded to an S3 bucket. We’re configuring the bucket in CloudFormation using the NotificationConfiguration > LambdaConfigurations > ObjectCreated > s3:ObjectCreated:* with a filter on the suffix. We want the lambda to be triggered whenever a png file is added to the bucket. We want this to happen for any casing of filename suffix e.g. .png or .PNG. Here is the CF

"NotificationConfiguration": {
      "LambdaConfigurations": [
        {
          "Event": "s3:ObjectCreated:*",
          "Filter": {
            "S3Key": {
              "Rules": [
                {
                  "Name": "suffix",
                  "Value": "PNG"
                }
              ]
            }
          }

The above ONLY works and triggers the Lambda for files with an uppercase suffix of "PNG", the lambda is not triggered for files with a suffix of "png".

How is it possible to make a suffix filter or filters or alternative approach that will trigger the Lambda regardless of suffix casing?

There’s relevant info here but it didn’t seem to solve this particular issue and it seems like a problem that would be encountered fairly often – https://docs.aws.amazon.com/AmazonS3/latest/userguide/notification-how-to-filtering.html

Thanks,

Sam

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2

Answers


  1. 0

    Amazon S3 file names (and the rules on the event notifications) are always case sensitive.

    If you can’t change your implementation, you need an intermediate Lambda Function that process every S3 Event Notification, filter it manually in a case-insensitive way, and then call the right function in the chain.

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  2. 0

    I was able to create an S3 bucket NotificationConfiguration that triggers an existing Lambda function when objects with suffix png or with suffix PNG are dropped into the S3 bucket.

    Here’s the YAML template (you can convert to JSON easily):

    AWSTemplateFormatVersion: "2010-09-09"
Description: Stack Overflow 75519656

Parameters:
  BucketName:
    Type: String
    Default: mybucket
  FunctionName:
    Type: String
    Default: print-event
  FunctionArn:
    Type: String
    Default: arn:aws:lambda:us-east-1:111122223333:function:print-event

Resources:
  LambdaInvokePermission:
    Type: AWS::Lambda::Permission
    Properties:
      FunctionName: !Ref FunctionName
      Action: lambda:InvokeFunction
      Principal: s3.amazonaws.com
      SourceAccount:
        Ref: AWS::AccountId
      SourceArn:
        Fn::Sub: arn:aws:s3:::${BucketName}
  Bucket:
    Type: AWS::S3::Bucket
    DependsOn: LambdaInvokePermission
    Properties:
      BucketName: !Ref BucketName
      NotificationConfiguration:
        LambdaConfigurations:
          - Event: s3:ObjectCreated:*
            Filter:
              S3Key:
                Rules:
                  - Name: suffix
                    Value: png
            Function: !Ref FunctionArn
          - Event: s3:ObjectCreated:*
            Filter:
              S3Key:
                Rules:
                  - Name: suffix
                    Value: PNG
            Function: !Ref FunctionArn
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