This demonstration is intended for participants that are interested in programming IoT systems. Modern distributed applications increasingly replicate data to guarantee both high availability of systems and an optimal user experience. Conflict-Free Replicated Datatypes (CRDTs) are a family of data types specially designed for highly available systems which guarantee a form of eventual consistency (i.e. Strong Eventual Consistency). However, a bulk of CRDT research has focused on providing formal specifications of different data types, but limited work has focused on the practical aspects of embedding CRDT in applications. Typically, many issues arise related to memory management and security when integrating CRDT specifications with existing applications and/or languages.

In this demonstration, we present Flec: a versatile programming framework for operation based CRDTs that can run on a variety of systems, including resource-limited IoT development platforms. Firstly, Flec provides a flexible networking framework that allows programs to work on different platforms. Moreover, it exposes CRDT internals through a Meta-Object Protocol (MOP) easing the development of new variants through reflection. We start the demonstration with a brief overview of CRDTs and operation-based CRDTs, the problems faced by developers when they want to integrate CRDTs with their applications, and more concretely the issues related to memory management. Then we introduce Flec, our framework that aims to tackle some of these problems. We will present a demo of Flec running on ESP32 IoT hardware platforms, which are severely restricted in resources. We will conclude with an interactive moment where the audience members can interact with the devices, and experiment with small ad-hoc Flec applications running on the ESP32s.