Designing Distributed Systems Using Approximate Synchrony in Data Center Networks
Designing Distributed Systems Using Approximate Synchrony in Data Center Networks
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2015-05
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分布式系统传统上是独立于底层网络设计的，对其行为做出最坏情况的假设（例如，完全异步）。然而，当今的许多分布式应用程序都部署在数据中心，那里的网络更加可靠、可预测和可扩展。在这些环境中，可以共同设计分布式系统及其网络层，这样做可以带来巨大的好处。本文探讨了提供多数有序多播 (MOM) 的网络级机制：并发多播操作的尽力而为的排序属性。使用这个原语，我们设计了 Speculative Paxos，这是一种状态机复制协议，在正常情况下依赖网络对请求进行排序。这种方法带来了巨大的性能优势：在实际数据中心条件下，Speculative Paxos 可以提供比标准 Paxos 协议低 40% 的延迟和高 2.6 倍的吞吐量。它提供比延迟优化协议（Fast Paxos）更低的延迟，并具有与吞吐量优化协议（批处理）相同的吞吐量。
Distributed systems are traditionally designed independently from the underlying network, making worst-case assumptions (e.g., complete asynchrony) about its behavior. However, many of today's distributed applications are deployed in data centers, where the network is more reliable, predictable, and extensible. In these environments, it is possible to co-design distributed systems with their network layer, and doing so can offer substantial benefits. This paper explores network-level mechanisms for providing Mostly-Ordered Multicast (MOM): a best-effort ordering property for concurrent multicast operations. Using this primitive, we design Speculative Paxos, a state machine replication protocol that relies on the network to order requests in the normal case. This approach leads to substantial performance benefits: under realistic data center conditions, Speculative Paxos can provide 40% lower latency and 2.6× higher throughput than the standard Paxos protocol. It offers lower latency than a latency-optimized protocol (Fast Paxos) with the same throughput as a throughput-optimized protocol (batching).