Distributed Consensus, Revisited

We provide a novel model to formalize a well-known algorithm, by Chandra and Toueg, that solves Consensus among asynchronous distributed processes in the presence of a particular class of failure detectors (Diamond S or, equivalently, Omega), under the hypothesis that only a minority of processes may crash. The model is defined as a global transition system that is unambigously generated by local transition rules. The model is syntax-free in that it does not refer to any form of programming language or pseudo code. We use our model to formally prove that the algorithm is correct

Coracle: Evaluating Consensus at the Internet Edge

ABSTRACT Distributed consensus is fundamental in distributed systems for achieving fault-tolerance. The Paxos algorithm has long dominated this domain, although it has been recently challenged by algorithms such as Raft and Viewstamped Replication Revisited. These algorithms rely on Paxos's original assumptions, unfortunately these assumptions are now at odds with the reality of the modern internet. Our insight is that current consensus algorithms have significant availability issues when deployed outside the well defined context of the datacenter. To illustrate this problem, we developed Coracle, a tool for evaluating distributed consensus algorithms in settings that more accurately represent realistic deployments. We have used Coracle to test two examples of network configurations that contradict the liveness claims of the Raft algorithm. Through the process of exercising these algorithms under more realistic assumptions, we demonstrate wider availability issues faced by consensus algorithms when deployed on real world networks

Coracle: Evaluating Consensus at the Internet Edge

ABSTRACT Distributed consensus is fundamental in distributed systems for achieving fault-tolerance. The Paxos algorithm has long dominated this domain, although it has been recently challenged by algorithms such as Raft and Viewstamped Replication Revisited. These algorithms rely on Paxos's original assumptions, unfortunately these assumptions are now at odds with the reality of the modern internet. Our insight is that current consensus algorithms have significant availability issues when deployed outside the well defined context of the datacenter. To illustrate this problem, we developed Coracle, a tool for evaluating distributed consensus algorithms in settings that more accurately represent realistic deployments. We have used Coracle to test two examples of network configurations that contradict the liveness claims of the Raft algorithm. Through the process of exercising these algorithms under more realistic assumptions, we demonstrate wider availability issues faced by consensus algorithms when deployed on real world networks

A Fixed Point Theory Approach to Multi-Agent Consensus Dynamics With Delays

The classic linear time-invariant multi-agent consensus scheme is revisited in the presence of constant and distributed bounded delays. We create a fixed point argument and prove exponential convergence with specific rate that depends both on the topology of the communication graph and the upper bound of the allowed delay

Missional Churches in Secular Societies: Theology Consults Sociology

The church is missionary by nature. But what about public church mission in secular societies? Furious religion mobilizing against rebarbative secularity? Withdrawal to seek exemplary perfection? To the contrary, theologically principled consultation with the sociology of J. Casanova on deprivatized religion leads to public witness in modern societies. Public theology can interpret deprivatized religion as an expression of prophetic and kingly elements in church mission. However, sociology leaves the priestly element as if private. What might ecclesiology, missiology, and public theology say about a public aspect of the priestly element in the church’s witness in modern societies

A Survey on Multisensor Fusion and Consensus Filtering for Sensor Networks

Multisensor fusion and consensus filtering are two fascinating subjects in the research of sensor networks. In this survey, we will cover both classic results and recent advances developed in these two topics. First, we recall some important results in the development ofmultisensor fusion technology. Particularly, we pay great attention to the fusion with unknown correlations, which ubiquitously exist in most of distributed filtering problems. Next, we give a systematic review on several widely used consensus filtering approaches. Furthermore, some latest progress on multisensor fusion and consensus filtering is also presented. Finally, conclusions are drawn and several potential future research directions are outlined.the Royal Society of the UK, the National Natural Science Foundation of China under Grants 61329301, 61374039, 61304010, 11301118, and 61573246, the Hujiang Foundation of China under Grants C14002 and D15009, the Alexander von Humboldt Foundation of Germany, and the Innovation Fund Project for Graduate Student of Shanghai under Grant JWCXSL140

Knowledge society arguments revisited in the semantic technologies era

In the light of high profile governmental and international efforts to realise the knowledge society, I review the arguments made for and against it from a technology standpoint. I focus on advanced knowledge technologies with applications on a large scale and in open- ended environments like the World Wide Web and its ambitious extension, the Semantic Web. I argue for a greater role of social networks in a knowledge society and I explore the recent developments in mechanised trust, knowledge certification, and speculate on their blending with traditional societal institutions. These form the basis of a sketched roadmap for enabling technologies for a knowledge society