Get input in Lambda from s3 event trigeer - amazon-web-services

Question

I am trying to trigger a Lambda once I get any file in an s3 bucket. For that I have configured the event in the s3 bucket. But, I need to give an input to the Lambda (event) that will be triggered. How do I do that?

Answer 1

Add a new Lambda function handler to the project. Create a new function handler name, say 'S3FunctionHandler'; use the default input type that is already selected, S3 Event; and as leave the output type as object:
This will create some boilerplate code with the Lambda function handler that takes an S3 event as input:
Select S3FunctionHandler and select an IAM Role:
Switch over to the AWS Management Console to test our Lambda function with a dummy S3 event. We need to test it, so to do this let's configure a test event. Select the S3 Put event, which you find by clicking on the Actions tab. This simulates somebody uploading a new object to an S3 bucket.

Answer 2

If an Amazon S3 Event is configured to trigger an AWS Lambda function, then S3 will provide information to the Lambda function about the S3 object that triggered the function.
From Using AWS Lambda with Amazon S3 - AWS Lambda:
{
"Records": [
{
"eventVersion": "2.1",
"eventSource": "aws:s3",
"awsRegion": "us-east-2",
"eventTime": "2019-09-03T19:37:27.192Z",
"eventName": "ObjectCreated:Put",
"userIdentity": {
"principalId": "AWS:AIDAINPONIXQXHT3IKHL2"
},
"requestParameters": {
"sourceIPAddress": "205.255.255.255"
},
"responseElements": {
"x-amz-request-id": "D82B88E5F771F645",
"x-amz-id-2": "vlR7PnpV2Ce81l0PRw6jlUpck7Jo5ZsQjryTjKlc5aLWGVHPZLj5NeC6qMa0emYBDXOo6QBU0Wo="
},
"s3": {
"s3SchemaVersion": "1.0",
"configurationId": "828aa6fc-f7b5-4305-8584-487c791949c1",
"bucket": {
"name": "my-bucket",
"ownerIdentity": {
"principalId": "A3I5XTEXAMAI3E"
},
"arn": "arn:aws:s3:::my-bucket"
},
"object": {
"key": "foo.jpg",
"size": 1305107,
"eTag": "b21b84d653bb07b05b1e6b33684dc11b",
"sequencer": "0C0F6F405D6ED209E1"
}
}
}
]
}
This information includes the Bucket name, Key (filename) of the object, the event that triggered the function and various other tidbits of information. The Lambda function can then use this information to process the object appropriately.