OB-STM: An Optimistic Approach for Byzantine Fault Tolerance in Software Transactional Memory

Abstract

Recently, researchers have shown an increased interest in concurrency control using distributed Software Transactional Memory (STM). However, there has been little discussion about certain types of fault tolerance, such as Byzantine Fault Tolerance (BFT), for kind of systems. The focus of this paper is on tolerating byzantine faults on optimistic processing of transactions using STM. The result is an algorithm named OB-STM. The processing of a transaction runs with an optimistic approach, benefiting from the high probability of messages being delivered in order when using Reliable Multicast on a local network (LAN). The protocol has a better performs when messages are delivered ordered. In case of a malicious replica or out-of-order messages, the Byzantine protocol is initiated. In smaller scenarios and using an optimistic approach, the protocol has a better throughput than Tazio.

Dealing with Interactive Transactions in a Byzantine Fault Tolerant STM

“…A execução otimista e não otimista das transações pré-declaradas, na ausência de transações interativas, segue fluxo idêntico ao protocolo OB-STM [15]. O Mesobí e uma evolução do protocolo OB-STM onde transações interativas e pré-declaradas concorrem pela execução, sendo que as transações interativas tem prioridade sobre as pré-declaradas.…”

“…O protocolo proposto no Mesobié baseado na execução paralela de transações não conflitantes, semelhante ao proposto por [14]. O presente trabalhoé uma evolução do OB-STM [15] que lida somente com transações pré-declaradas.…”

“…: upon: receive( P RE−P REP ARE, Ri, Order, OrderT X, v, n, d σ) if (PRE-PREPARE was accepted) then 3: for all (R ∈ Q R minus his own replica) do TO-Deliver( P REP ARE, Ri, Order, OrderT X, v, n, d σ) upon: receive( P REP ARE, Ri, Order, OrderT X, v, n, d σ) from TO-Deliver( COMMIT − ORDER, Ri, Order, OrderT X, v, n, d σ) Ri, Order, OrderT X, v, n, d σ) from replicas 12: if (COMMIT-ORDER was accepted) then Set all T ∈ BCO as Work in Progress (WiP)15:for all (T Xi ∈ OrderT X) do 16: if (T Xi Can Commit) then 17: Call COMMIT-TX(T Xi) Call ABORT-TX(T Xi) Call NEXT-T-EXEC() 21: function ABORT-TX(T Xi) 22: Abort transaction T Xi! 23: Q T XBegin ← Q T XBegin \T Xi.Begin BCO ← BCO \ Ti32:Call RE-EXEC-T(getFirstElement(BCO))Figura 6: Transações pré-declaradas e interativas, com conflito de dados.…”