AWS Lambda Handler extend S3event - json

Question

I have the following pipeline:
A file is uploaded to S3, it triggers a Lambda (Let's call it L1) which runs and does some processing.
So at the moment, my entry point looks like this:
public Response handleRequest(S3Event event, Context context) {
....
}
Now, a S3Event JSON looks like this:
{
"Records": [
{
"awsRegion": "xxxxx",
"eventName": "ObjectCreated:Put",
"eventSource": "aws:s3",
"eventTime": "2017-09-12T09:27:59.471Z",
"eventVersion": "2.0",
"requestParameters": {
"sourceIPAddress": "xxxxxx"
},
"responseElements": {
"x-amz-id-2": "xxxxxx",
"x-amz-request-id": "xxxx"
},
"s3": {
"configurationId": "xxxxxx1",
"bucket": {
"name": "xxxxx",
"ownerIdentity": {
"principalId": "xxxxx"
},
"arn": "xxx"
},
"object": {
"key": "xxx",
"size": xxx,
"eTag": "xxxx",
"versionId": null,
"sequencer": "xxx",
"urlDecodedKey": "xxx"
},
"s3SchemaVersion": "1.0"
},
"userIdentity": {
"principalId": "xxxx"
}
}
],
}
If you pass this JSON in the "Test" section, it will succeed.
Now, to the point: I wish to add information to this JSON, something that would look like this:
{
"Records": [
{
"awsRegion": "xxxxx",
"eventName": "ObjectCreated:Put",
"eventSource": "aws:s3",
"eventTime": "2017-09-12T09:27:59.471Z",
"eventVersion": "2.0",
"requestParameters": {
"sourceIPAddress": "xxxxxx"
},
"responseElements": {
"x-amz-id-2": "xxxxxx",
"x-amz-request-id": "xxxx"
},
"s3": {
"configurationId": "xxxxxx1",
"bucket": {
"name": "xxxxx",
"ownerIdentity": {
"principalId": "xxxxx"
},
"arn": "xxx"
},
"object": {
"key": "xxx",
"size": xxx,
"eTag": "xxxx",
"versionId": null,
"sequencer": "xxx",
"urlDecodedKey": "xxx"
},
"s3SchemaVersion": "1.0"
},
"userIdentity": {
"principalId": "xxxx"
}
}
],
"MyErrorMessage":
{
"EnvelopeErrors": [
{
"EnvelopeErrorTrace": "stackTrace",
"EnvelopeErrorPositions": 1,
"EnvelopeErrorLength": 2
},
{
"EnvelopeErrorTrace": "SecondTrace",
"EnvelopeErrorPositions": 3,
"EnvelopeErrorLength": 4
}
],
}
}
Notice is the S3Event JSon but with a bit more data.
My question problem is the following: I want to have a custom input that also works when a pure S3Event is called.
public Response handleRequest(MyS3Event event, Context context) {
....
}
However, I have not been able to achieve this.
I have tried a custom POJO but it does not work when I upload to S3 a file.
I tried to extend the S3EventNotification class (from which S3Event extends), but again with no success.
Is it possible what I am trying to do?

Answer 1

What you can do is to have your Lambda (L1) call itself (asynchronously) by sending it the new, modified event similar to how recursive functions work.
Just be very careful though. You have to put a limit as to how deep you want to keep recursing. You don't want to end up with infinite calls. I am not sure if AWS guards against this.

Answer 2

In the AWS SDK Lambda has an invoke method:
Invokes a specific Lambda function. For an example, see Create the Lambda Function and Test It Manually.
If you are using the versioning feature, you can invoke the specific
function version by providing function version or alias name that is
pointing to the function version using the Qualifier parameter in the
request. If you don't provide the Qualifier parameter, the $LATEST
version of the Lambda function is invoked. Invocations occur at least
once in response to an event and functions must be idempotent to
handle this. For information about the versioning feature, see AWS Lambda Function Versioning and Aliases.
This operation requires permission for the lambda:InvokeFunction
action.
var params = {
FunctionName: 'STRING_VALUE', /* required */
ClientContext: 'STRING_VALUE',
InvocationType: Event | RequestResponse | DryRun,
LogType: None | Tail,
Payload: new Buffer('...') || 'STRING_VALUE',
Qualifier: 'STRING_VALUE'
};
lambda.invoke(params, function(err, data) {
if (err) console.log(err, err.stack); // an error occurred
else console.log(data); // successful response
});
One of the params you send a Payload which is the event the invoked function receives so you can send your MyErrorMessage in/as this payload to get the desired result.