Handle timeout in AWS API Gateway

Question

I'm working on a project were I'm using a lambda function to connect to a relational database and to DynamoDB at the same time. To access that function I'm using API Gateway, but I found a problem: My lambda function, written in Java takes more than 10 seconds to start due to the creation of both database connections.

I know API Gateway timeout is 10 seconds, and that's not a problem executing my function witch takes less than 1 second, but the problem is when it has to start. I would like to know how to catch this timeout exception and notify to the user that he needs to start the request again.

Is there a way to do so without moving to Node.js or accessing lambda function directly?

Answer 1

Since the cost of establishing a connection to a relational database is so high, I would encourage you to open the connection in the initialization code of your Lambda function (outside of the handler).

The database connection will then be re-used across multiple invocations for the lifetime of the Lambda container. Within your Lambda function handler you may want to ensure the connection is alive and hasn't timed out, and re-open as required.

The first call through API Gateway may timeout, but subsequent calls will reuse the connection for the lifetime of the container.

Another trick is to create a scheduled function to periodically call your function to keep the container "warm".

Cheers, Ryan