  As we approach the exascale era, the size and complexity of HPC systems
continues to increase, raising concerns about their manageability and
sustainability. For this reason, more and more HPC centers are experimenting
with fine-grained monitoring coupled with Operational Data Analytics (ODA) to
optimize efficiency and effectiveness of system operations. However, while
monitoring is a common reality in HPC, there is no well-stated and
comprehensive list of requirements, nor matching frameworks, to support
holistic and online ODA. This leads to insular ad-hoc solutions, each
addressing only specific aspects of the problem.
  In this paper we propose Wintermute, a novel generic framework to enable
online ODA on large-scale HPC installations. Its design is based on the results
of a literature survey of common operational requirements. We implement
Wintermute on top of the holistic DCDB monitoring system, offering a large
variety of configuration options to accommodate the varying requirements of ODA
applications. Moreover, Wintermute is based on a set of logical abstractions to
ease the configuration of models at a large scale and maximize code re-use. We
highlight Wintermute's flexibility through a series of practical case studies,
each targeting a different aspect of the management of HPC systems, and then
demonstrate the small resource footprint of our implementation.
