Need to understand step function retry mechanism

Question

May be this can be answered quickly. I am working on adding a retry mechanism in step functions. I want to keep retrying the failed activity for 24 hours at a interval of 1 hour or so.

I was going thorough the "Retrying after an error" section here: https://docs.aws.amazon.com/step-functions/latest/dg/concepts-error-handling.html It says that "The multiplier by which the retry interval increases during each attempt (2.0 by default)." And also given example of 1st retry after 3 secs and next retry after 4.5 secs because, BackoffRate is 1.5.

So is this not exponential backoff? Because, on the same page, under "Handling a failure using Retry" section, it says the backoff will be applied exponentially.

Answer 1

Here is how interval between retry works:

Interval = IntervalSeconds*(BackoffRate)^(attempt-1)

So for this config:

      "Retry": [
        {
          "ErrorEquals": ["States.ALL"],
          "BackoffRate": 2,
          "IntervalSeconds": 6,
          "MaxAttempts": 6
        }
      ]

We have these intervals:

attempt.      interval
---------------------------
1             6*(2^0)  =  6
2             6*(2^1)  =  12
3             6*(2^2)  =  24