Supporting fault-tolerant parallel programming in Linda.

Abstract

As people are becoming increasingly dependent on computerized systems, the need for these systems to be dependable is also increasing. However, programming dependable systems is difficult, especially when parallelism is involved. This is due in part to the fact that very few high-level programming languages support both fault-tolerance and parallel programming. This dissertation addresses this problem by presenting FT-Linda, a high-level language for programming fault-tolerant parallel programs. FT-Linda is based on Linda, a language for programming parallel applications whose most notable feature is a distributed shared memory called tuple space. FT-Linda extends Linda by providing support to allow a program to tolerate failures in the underlying computing platform. The distinguishing features of FT-Linda are stable tuple spaces and atomic execution of multiple tuple space operations. The former is a type of stable storage in which tuple values are guaranteed to persist across failures, while the latter allows collections of tuple operations to be executed in an all-or-nothing fashion despite failures and concurrency. Example FT-Linda programs are given for both dependable systems and parallel applications. The design and implementation of FT-Linda are presented in detail. The key technique used is the replicated state machine approach to constructing fault-tolerant distributed programs. Here, tuple space is replicated to provide failure resilience, and the replicas are sent a message describing the atomic sequence of tuple space operations to perform. This strategy allows an efficient implementation in which only a single multicast message is needed for each atomic sequence of tuple space operations. An implementation of FT-Linda for a network of workstations is also described. FT-Linda is being implemented using Consul, a communication substrate that supports fault-tolerant distributed programming. Consul is built in turn with the x-kernel, an operating system kernel that provides support for composing network protocols. Each of the components of the implementation has been built and tested.