The paper "DDS Implementations as Real-Time Middleware – A Systematic Evaluation", a result of a TUM collaboration with Siemens, was accepted at the RTCSA23 conference.
Abstract—Publish-subscribe messaging has seen increased
adoption in the context of timing critical applications, with
multiple frameworks integrating publish-subscribe middleware
into their ecosystem. The Data Distribution Service (DDS) is a
standard for pub-sub systems that has gained traction, through
e.g. the adoption in ROS2, with multiple vendors distributing
their implementations of the standard. However, while DDS is
being used in a real-time context, the examined implementations
are not strictly real-time capable and therefore cannot provide
hard timing guarantees to the application.
Still, users are looking
to take advantage of the flexibility offered by DDS in close-
to real-time use cases, raising the question of how well DDS
implementations can provide soft real-time reliability assurances.
We use DDS-Perf, a novel cross-vendor benchmarking tool for
impartial performance analysis of DDS implementations, to ex-
amine how reliably four vendors (OpenDDS, RTI Connext, Fast-
DDS and CycloneDDS) can deliver real-time-like performance
under different scenarios. From a typical out-of-the-box setup,
we offer a guide to users for tuning performance/reliability and
examine problems users might encounter trying to satisfy real-
time constraints.
The vendor implementations are tested against
a range of experiments to evaluate operating performance under
favorable and adverse conditions. Overall, we find that OpenDDS
has the worst performance out-of-the-box and after calibration,
while FastDDS and CycloneDDS offer the best performance,
which is comparable to user-space networking technologies in the
average case but with a much higher worst-case latency bound.