  In the context of the BI-REX (Big Data Innovation and Research Excellence)
competence center SEAWALL (SEAmless loW lAtency cLoud pLatforms) project
(scientific coordinator Prof. Maurizio Gabbrielli) we develop a novel approach
for run-time global adaptation of microservice applications, based on synthesis
of architecture-level reconfiguration orchestrations. More precisely, we devise
an algorithm for automatic reconfiguration that reaches a target system Maximum
Computational Load by performing optimal deployment orchestrations. To conceive
and simulate our approach, we introduce a novel integrated timed architectural
modeling/execution language based on an extension of the actor-based
object-oriented Abstract Behavioral Specification (ABS) language. In
particular, we realize a timed extension of SmartDeployer, whose ABS code
annotations make it possible to express architectural properties. Our Timed
SmartDeployer tool fully integrates time features of ABS and architectural
annotations by generating timed deployment orchestrations. We evaluate the
applicability of our approach on a realistic microservice application taken
from the literature: an Email Pipeline Processing System. We prove its
effectiveness by simulating such an application and by comparing
architecture-level reconfiguration with traditional local scaling techniques
(which detect scaling needs and enact replications at the level of single
microservices). Our comparison results show that our approach avoids cascading
slowdowns and consequent increased message loss and latency, which affect
traditional local scaling.
