  Predictive Autoscaling is used to forecast the workloads of servers and
prepare the resources in advance to ensure service level objectives (SLOs) in
dynamic cloud environments. However, in practice, its prediction task often
suffers from performance degradation under abnormal traffics caused by external
events (such as sales promotional activities and applications
re-configurations), for which a common solution is to re-train the model with
data of a long historical period, but at the expense of high computational and
storage costs. To better address this problem, we propose a replay-based
continual learning method, i.e., Density-based Memory Selection and Hint-based
Network Learning Model (DMSHM), using only a small part of the historical log
to achieve accurate predictions. First, we discover the phenomenon of sample
overlap when applying replay-based continual learning in prediction tasks. In
order to surmount this challenge and effectively integrate new sample
distribution, we propose a density-based sample selection strategy that
utilizes kernel density estimation to calculate sample density as a reference
to compute sample weight, and employs weight sampling to construct a new memory
set. Then we implement hint-based network learning based on hint representation
to optimize the parameters. Finally, we conduct experiments on public and
industrial datasets to demonstrate that our proposed method outperforms
state-of-the-art continual learning methods in terms of memory capacity and
prediction accuracy. Furthermore, we demonstrate remarkable practicability of
DMSHM in real industrial applications.
