Consistency Mechanisms in Distributed Systems with a comparison between Distributed Lock Managers and Leases

Consistency Mechanisms in Distributed Systems with a comparison between Distributed Lock Managers and Leases

Abstract:

Current trends in computing technologies are drifting towards distributed and parallel computing. These topologies emphasize on concurrent access schemes. Because of distributed computing, the use of shared resources like databases, memory, etc. is growing. Locking mechanisms can be used effectively to achieve high concurrency levels without corrupting the resources. There are a wide range of synchronization protocols, some providing strong consistency while others granting weak consistency. There is a trade-off between complexity and the level of consistency offered by these locking mechanisms. In this report I describe two locking mechanisms appropriate for the consistency requirements of distributed computing environments, viz. Distributed Lock Managers (DLM’s) and Leases. Distributed lock managers leverage conventional client-server locking mechanisms to adapt them to distributed backgrounds. They present strong consistency but are complex in implementation. Leases are time-based protocols and are a hybrid version of server-based and client-based locking strategies. I have compared these two approaches and proposed suitable use cases for these architectures.

Introduction:

Several trends anticipate properties of future distributed systems. Systems are being extended over wider-area networks, the speed of processors also continues to grow. Finally, larger numbers of hosts, both clients and servers, are being tied together within a single system. The increase in the use of distributed systems necessitates proper functioning of consistency mechanisms. Various nodes within the system can have concurrent access to shared resources. It is required that they all get a consistent view of the resources. For this reason, when one node is writing to such resources, no other nodes should get access to the same resource. This can be achieved through locking mechanisms.


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