Software Transactional Memory (STM) systems have emerged as a powerful paradigm to develop concurrent applications. At current date, however, the problem of how to build distributed and replicated STMs to enhance both dependability and performance is still largely unexplored. This time by a non-blocking distributed certification scheme, which we name BFC (Bloom Filter Certification). BFC exploits a novel Bloom Filter-based encoding mechanism that permits to significantly reduce the overheads of replica coordination at the cost of a user tunable increase in the probability of transaction abort. Through an extensive experimental study based on standard STM benchmarks we show that the BFC scheme permits to achieve remarkable performance gains even for negligible (e.g. 1%) increases of the transaction abort rate.

For many distributed applications, the Publish-Subscribe communication model emerges as a viable alternative to the Request-Reply model. It provides a strong decoupling among participants, simplify the reutilization of components and the non-stop reconfiguration of applications. Unfortunately, this strong decoupling also makes it hard to support Quality of Service (QoS) parameters, like bandwidth and latency, in an efficient manner. This paper presents a novel approach to support QoS parameters in publish-subscribe systems. It proposes a model that supports the decoupling of QoS characterization from the event characterization while offering, at the same time, an uniform treatment of both aspects. Furthermore, it describes the architecture of a distributed and scalable publish-subscribe broker with support for QoS. The broker, called IndiQoS, leverages on existing mechanisms to reserve resources in the underlying network and on an overlay network of peer-to-peer rendezvous nodes, to automatically select QoS-capable paths. By avoiding flooding of either QoS reservations or link-state information, IndiQoS is able to scale with respect to network size and number of reservations. Experimental results show the validity of our approach.

The recent architectural trend that has lead to the widespread adoption of multi-core CPUs has fostered a remarkable research interest in Software Transactional Memory (STM). As STMs are starting to face the high availability and scalability requirements of real-world production environments, it is natural to foresee the need for replication solutions specifically tailored for STMs. Since databases and STMs share the same key abstraction of atomic transaction, one could wonder whether the mechanisms originally designed for database replication could be successfully and seamlessly exploited also to support replication of STM systems.This paper seeks an answer to this question, highlighting some critical performance issues related to the application of state of the art database replication techniques in the context of STM systems, and presenting some of our recent research directions aimed at designing and implementing high performance replication strategies able to meet the unique requirements of STMs.

Abstract. Software Transactional Memory (STM) systems have emerged as a powerful middleware paradigm for parallel programming. At current date, however, the problem of how to leverage replication to enhance dependability and scalability of STMs is still largely unexplored. In this paper we present Asynchronous Lease Certification (ALC), an innovative STM replication scheme that exploits the notion of asynchronous lease to reduce the replica coordination overhead and shelter transactions from repeated abortions due to conflicts originated on remote nodes. These features allow ALC to achieve up to a tenfold reduction of the commit latency phase in scenarios of low contention when compared with state of the art faulttolerant replication schemes, and to boost the throughput of long-running transactions by a 4x factor in high conflict scenarios.

Sepsis is a life-threatening organ dysfunction condition caused by a dysregulated host response to an infection. Here we report that the circulating levels of growth and differentiation factor-15 (GDF15) are strongly increased in septic shock patients and correlate with mortality. In mice, we find that peptidoglycan is a potent ligand that signals through the TLR2-Myd88 axis for the secretion of GDF15, and thatGdf15-deficient mice are protected against abdominal sepsis due to increased chemokine CXC ligand 5 (CXCL5)-mediated recruitment of neutrophils into the peritoneum, leading to better local bacterial control. Our results identify GDF15 as a potential target to improve sepsis treatment. Its inhibition should increase neutrophil recruitment to the site of infection and consequently lead to better pathogen control and clearance.

Abstract-In this paper we investigate the problem of speculative processing in a replicated transactional system layered on top of an optimistic atomic broadcast service. We consider a realistic model in which transactions' read/write sets are not known a-priori, and transactions' data access patterns may vary depending on the observed snapshot. We formalize a set of correctness and optimality properties aimed at ensuring that transactions are not activated on inconsistent snapshots, as well as the minimality and completeness of the set of explored serialization orders. Finally, an optimal speculative transaction replication protocol is presented.

In epidemic or gossip-based multicast protocols, each node simply relays each message to some random neighbors, such that all destinations receive it at least once with high probability. In sharp contrast, structured multicast protocols explicitly build and use a spanning tree to take advantage of efficient paths, and aim at having each message received exactly once. Unfortunately, when failures occur, the tree must be rebuilt. Gossiping thus provides simplicity and resilience at the expense of performance and resource efficiency. In this paper we propose a novel technique that exploits knowledge about the environment to schedule payload transmission when gossiping. The resulting protocol retains the desirable qualities of gossip, but approximates the performance of structured multicast. In some sense, instead of imposing structure by construction, we let it emerge from the operation of the gossip protocol. Experimental evaluation shows that this approach is effective even when knowledge about the environment is only approximate.

Recently, third party solutions for database replication have been enjoying an increasing popularity. Such proposals address a diversity of user requirements, namely preventing conflicting updates without the overhead of synchronous replication; clustering for scalability and availability; and heterogeneous replicas for specialized queries. Unfortunately, the lack of native support from database vendors for third party replication forces implementors to either modify the database server, restricting portability, or to develop a middleware wrapper, which causes a performance overhead. This paper addresses this problem with a novel architecture and programming interface for replication, such that different strategies can be efficiently implemented on * Parts of this extended report were published in the Proceedings of the 6th IEEE Internacional Symposium on Network Computing and Applications (NCA '07), Boston, MA, USA. 2007. any compliant database management system in a cost-effective manner. The contribution is twofold. First we propose a reflective model of transaction processing and explain how it can be used to achieve replication. Then we implement the proposed architecture in Apache Derby, PostgreSQL, and Sequoia and evaluate the PostgreSQL implementation with the TPC-W industry standard benchmark.