AWS Lambda：一个 Lambda 函数是否可以同时具有 Kinesis 和 DynamoDB Streams 的事件源？

Question

Can one AWS Lambda function have two Event Sources both of one Kinesis stream and one DynamoDB Stream?

I've looked but I haven't found any documentation which says that I can or cannot have different types of event sources for the same AWS Lambda function.

Answer 1

Yes a lambda functions can have event sources of different types but you must use the com.amazonaws.services.lambda.runtime.RequestStreamHandler to be able to correctly deserialize the input data. This is because the internal lambda code that invokes com.amazonaws.services.lambda.runtime.RequestHandler won't deserialize the data dynamically based on types then invoke an overloaded method with correct type, but instead seems to reflectively pick a method and invoke it.

Sample inputs:

Kinesis Event input:

{
    "Records": [
        {
            "kinesis": {
                "kinesisSchemaVersion": "1.0",
                "partitionKey": "1",
                "sequenceNumber": "11111111111111111111111111111111111111111111111111111111",
                "data": "e30=",
                "approximateArrivalTimestamp": 1518397399.55
            },
            "eventSource": "aws:kinesis",
            "eventVersion": "1.0",
            "eventID": "shardId-000000000000:11111111111111111111111111111111111111111111111111111111",
            "eventName": "aws:kinesis:record",
            "invokeIdentityArn": "arn:aws:iam::111111111111:role/lambda_test-lambda-multipe-sources",
            "awsRegion": "us-east-1",
            "eventSourceARN": "arn:aws:kinesis:us-east-1:111111111111:stream/test-lambda-multipe-sources"
        }
    ]
}

DynamoDb Stream Record:

{
    "Records": [
        {
            "eventID": "11111111111111111111111111111111",
            "eventName": "INSERT",
            "eventVersion": "1.1",
            "eventSource": "aws:dynamodb",
            "awsRegion": "us-east-1",
            "dynamodb": {
                "ApproximateCreationDateTime": 1518397440,
                "Keys": {
                    "key": {
                        "S": "asdf"
                    }
                },
                "NewImage": {
                    "key": {
                        "S": "asdf"
                    }
                },
                "SequenceNumber": "111111111111111111111111",
                "SizeBytes": 14,
                "StreamViewType": "NEW_AND_OLD_IMAGES"
            },
            "eventSourceARN": "arn:aws:dynamodb:us-east-1:111111111111:table/test-lambda-multipe-sources/stream/2018-02-11T18:57:44.017"
        }
    ]
}

Sample code:

public final class MultipleEventSourcesRequestHandler
        implements RequestHandler<KinesisEvent, Void>
//        implements RequestStreamHandler
{
    private static final Logger LOG = LoggerFactory.getLogger(MultipleEventSourcesRequestHandler.class);

    public Void handleRequest(final DynamodbEvent input, final Context context)
    {
        LOG.info("In DynamodbEvent handler with event of source: " + input.getRecords().get(0).getEventSource());
        return null;
    }

//    public final void handleRequest(final InputStream input, final OutputStream output, final Context context)
//            throws IOException
//    {
//        final byte[] serializedSpeechletRequest = IOUtils.toByteArray(input);
//        LOG.info("In Stream handler. Request bytes: " + new String(serializedSpeechletRequest, StandardCharsets.UTF_8));
//        output.close();
//    }

    public Void handleRequest(final KinesisEvent input, final Context context)
    {
        LOG.info("In KinesisEvent handler with event of source: " + input.getRecords().get(0).getEventSource());
        return null;
    }
}

Sample logs:

2018-02-12 01:32:57 INFO (main) com.example.lambda.eventsourcetest.MultipleEventSourcesRequestHandler - In KinesisEvent handler with event of source: aws:dynamodb