Rollback recovery is a recovery class that ensures that failures do not cause information loss. More specifically, it guarantees that the effects of all input elements are always preserved until Odysseus can continue processing the elements (at-least-once). Therefore, rollback recovery techniques result in a complete output stream (relative to its failure-free counterpart), but typically they result also in duplicate values (all values between the last checkpoint and the system failure). (Reference: J.H. Hwang et al., High-Availability Algorithms for Distributed Stream Processing, 2005)
In Odysseus, the rollback recovery uses an external application, Backup of Data Streams (BaDaSt), that preserves all incoming elements after the last checkpoint
Documentation under progress.