AWS Step Functions: how to deal with AWS API endpoints which support pagination

Question

Hello,

I am using AWS Step Functions with the new AWS SDK integrations. I am wondering how to deal with API endpoints which return only a limit number of items like for instance "rds:describePendingMaintenanceActions" so that following requests using the "NextToken" value are required to get all data. Is there any construct/suggestion available how to model this. I am aware that I can use a *Choice* state in order to check if "NextToken" is empty or not and to act accordingly (go back to the API request step and repeat the whole process with the *NextToken* value) but this feels somehow clumsy. Thank you very much for any information.

Accepted Answer

What you suggest is the right way to go at the moment, i.e., run the loop yourself and use a Choice state to check if the NextToken is empty as an exit criteria from the loop. If you need to do it in different places, maybe it is possible to do it with a nested workflow to run the loop.

Answer

Lambda supports up to [15 min execution time as of October 18, 2018](https://aws.amazon.com/about-aws/whats-new/2018/10/aws-lambda-supports-functions-that-can-run-up-to-15-minutes/). You could process the next tokens in the function itself.

Answer

We use the same technique: We want to load > 1 million data sets from a database and process it with different lambda functions and do some other stuff with it. Therefore, we use a choice state with a loop within the step functions and have an "iterator" step that is loading new data right after the choice.

Seems like I can not add an image here, I'm sorry :)

I would NOT go the way Rodney Lester suggests to do the looping in Lambda as you do not have retries over certain batches for example.

AWS Step Functions: how to deal with AWS API endpoints which support pagination

Relevant content