A Study of Implementation Methodologies for Distributed Real Time Collaboration

Collaboration drives our world and is almost unavoidable in the programming industry. From higher education to the top technological companies, people are working together to drive discovery and innovation. Software engineers must work with their peers to accomplish goals daily in their workplace. When working with others there are a variety of tools to choose from such as Google Docs, Google Colab and Overleaf. Each of the aforementioned collaborative tools utilizes the Operational Transform (OT) technique in order to implement their real time collaboration functionality. Operational transform is the technique seen amongst most if not all major collaborative tools in our industry today. However, there is another way of implementing real time collaboration through a data structure called Conflict-free Replicated Data Type (CRDT) which has made claims of superiority over OT. Previous studies have taken place with the focus on comparing the theory behind OT and CRDT\u27s, but as far as we know, there have not been studies which compare real time collaboration performance using an OT implementation versus a CRDT implementation in a popularly used product such as Google Docs or Overleaf. Our work will focus on comparing OT and CRDT\u27s real time collaborative performance in Overleaf, an academic authorship tool, which allows for easy collaboration on academic and professional papers. Overleaf\u27s current published version implements real time collaboration using operational transform. This thesis will contribute an analysis of the current real time collaboration performance of operational transform in Overleaf, an implementation of CRDT\u27s for real time collaboration in Overleaf and an analysis of the performance of real time collaboration through the CRDT implementation in Overleaf. This thesis describes the main advantages and disadvantages of OT vs CRDTs, as well as, to our knowledge, the first results of a non-theoretical attempt at implementing CRDTs for handling document edits in a collaborative environment which was originally operating using an OT implementation

The Art of the Fugue: Minimizing Interleaving in Collaborative Text Editing

Most existing algorithms for replicated lists, which are widely used in collaborative text editors, suffer from a problem: when two users concurrently insert text at the same position in the document, the merged outcome may interleave the inserted text passages, resulting in corrupted and potentially unreadable text. The problem has gone unnoticed for decades, and it affects both CRDTs and Operational Transformation. This paper defines maximal non-interleaving, our new correctness property for replicated lists. We introduce two related CRDT algorithms, Fugue and FugueMax, and prove that FugueMax satisfies maximal non-interleaving. We also implement our algorithms and demonstrate that Fugue offers performance comparable to state-of-the-art CRDT libraries for text editing.Comment: 16 pages, 10 figure

Collabs: A Flexible and Performant CRDT Collaboration Framework

A collaboration framework is a distributed system that serves as the data layer for a collaborative app. Conflict-free Replicated Data Types (CRDTs) are a promising theoretical technique for implementing collaboration frameworks. However, existing frameworks are inflexible: they are often one-off implementations of research papers or only permit a restricted set of CRDT semantics, and they do not allow app-specific optimizations. Until now, there was no general framework that lets programmers mix, match, and modify CRDTs. We solve this with Collabs, a CRDT-based collaboration framework that lets programmers implement their own CRDTs, either from-scratch or by composing existing building blocks. Collabs prioritizes both semantic flexibility and performance flexibility: it allows arbitrary app-specific CRDT behaviors and optimizations, while still providing strong eventual consistency. We demonstrate Collabs's capabilities and programming model with example apps and CRDT implementations. We then show that a collaborative rich-text editor using Collabs's built-in CRDTs can scale to over 100 simultaneous users, unlike existing CRDT frameworks and Google Docs. Collabs also has lower end-to-end latency and server CPU usage than a popular Operational Transformation framework, with acceptable CRDT metadata overhead.Comment: 18 pages, 19 figure

A Web Component for Real-Time Collaborative Text Editing

Real-time collaborative software allows physically distinct people to co-operate by working on a shared application state, receiving updates from each other in real-time. The goal of this thesis was to create a developer tool, which would allow web application developers to easily integrate a collaborative text editor into their applications. In order to remain technology agnostic and to utilize the latest web standards, this product was implemented as a web component, a reusable user interface component built with native web browser features. The main challenge in developing a real-time collaboration tool is the handling of concurrent updates, which might conflict with one another. To tackle this issue, many consistency maintenance algorithms have been presented in the academic literature. Most of these techniques are variations of two main approaches: operational transformation and commutative replicated data types. In this thesis, we reviewed some of these methods and chose the GOTO operational transformation algorithm to be implemented in our component. Besides selecting and implementing an appropriate consistency maintenance technique, the contributions of this thesis include the design of an easy-to-use application programming interface (API). Our solution also fulfills some practical requirements of group editors not covered by the consistency maintenance theory, such as session management and cleaning of the message queue. The created web component succeeds in encapsulating the complexity related to concurrency control and handling of joining peers in the client-side implementation, which allows the application logic to remain simplistic. This open-source product enables software developers to add a collaborative text editor to their web applications by broadcasting the updates provided by an event-based API to participating peers

Total order in opportunistic networks

Opportunistic network applications are usually assumed to work only with unordered immutable messages, like photos, videos, or music files, while applications that depend on ordered or mutable messages, like chat or shared contents editing applications, are ignored. In this paper, we examine how total ordering can be achieved in an opportunistic network. By leveraging on existing dissemination and causal order algorithms, we propose a commutative replicated data type algorithm on the basis of Logoot for achieving total order without using tombstones in opportunistic networks where message delivery is not guaranteed by the routing layer. Our algorithm is designed to use the nature of the opportunistic network to reduce the metadata size compared to the original Logoot, and even to achieve in some cases higher hit rates compared to the dissemination algorithms when no order is enforced. Finally, we present the results of the experiments for the new algorithm by using an opportunistic network emulator, mobility traces, and Wikipedia pages.Peer ReviewedPostprint (author's final draft