attempt
0-indexed position in the retry sequence. attemptIndex == 0 is the original attempt (whose failure triggered the first retry); attemptIndex == 1 is the first retry attempt that itself failed; and so on.
0-indexed position in the retry sequence. attemptIndex == 0 is the original attempt (whose failure triggered the first retry); attemptIndex == 1 is the first retry attempt that itself failed; and so on.