Scaling Distributed Protocols Through Correct-by-Construction Query Rewrites

Core Concepts

Distributed protocols like 2PC and Paxos can be optimized for scalability through rule-driven query rewrites that preserve correctness.

Abstract

The paper presents an approach for scaling distributed protocols by applying rule-driven rewrites, borrowing from query optimization techniques. The key ideas are:
Decoupling:

Partitions code by breaking a single-node component into multiple components that can run in parallel across nodes.
Leverages order-insensitivity and data dependency analysis to identify correct coordination-free decoupling opportunities.
Partitioning:

Distributes data across nodes to parallelize compute.
Utilizes relational techniques like functional dependency analysis to find data partitioning schemes that allow sub-programs to work on local partitions without reshuffling.
The authors demonstrate the generality of their optimizations by applying them to three seminal distributed protocols: voting, 2PC, and Paxos. The optimized protocols achieve 2-5x throughput improvement compared to the unoptimized versions, matching the performance of state-of-the-art ad hoc rewrites.

Stats

Throughput of voting protocol scales from 50K to 200K commands/sec with 5 partitions.
Throughput of 2PC scales from 75K to 175K commands/sec with 5 partitions.
Throughput of Paxos scales from 50K to 150K commands/sec with 5 partitions.

Quotes

"Distributed protocols such as 2PC and Paxos lie at the core of many systems in the cloud, but standard implementations do not scale."
"Our local-first approach naturally has a potential cost: the space of protocol optimization is limited by design as it treats the initial implementation as 'law'."

Key Insights Distilled From

Optimizing Distributed Protocols with Query Rewrites [Technical Report]

by David Chu,Ri... at arxiv.org 04-03-2024

https://arxiv.org/pdf/2404.01593.pdf

Deeper Inquiries

How can the rule-driven rewrite approach be extended to handle more complex distributed protocols beyond 2PC and Paxos?

To extend the rule-driven rewrite approach to more complex distributed protocols, we can follow a systematic analysis of the protocol's logic and dependencies. By breaking down the protocol into its fundamental components and identifying the key data dependencies, we can create rules that optimize the protocol's performance without compromising correctness. This approach involves identifying opportunities for decoupling and partitioning within the protocol to scale it effectively. Additionally, we can explore the use of functional dependencies and co-partition dependencies to enable coordination-free partitioning of data across nodes. By applying these principles to more intricate protocols, we can ensure that the rule-driven rewrite approach is scalable and adaptable to a wide range of distributed systems.

What are the limitations of the local-first approach, and how could it be relaxed to explore a broader space of protocol optimizations?

The local-first approach, while effective in ensuring the preservation of protocol invariants and semantics, has limitations in terms of the space of potential optimizations it can explore. One major limitation is that it treats the initial implementation as the ultimate authority, potentially missing out on opportunities for more significant optimizations that may involve restructuring the protocol logic more extensively. To relax these limitations and explore a broader space of protocol optimizations, the local-first approach could be augmented with a more dynamic analysis of the protocol's behavior. This could involve incorporating dynamic profiling and monitoring of the protocol's performance to identify bottlenecks and areas for improvement. Additionally, introducing a feedback loop mechanism that allows for iterative refinement of the optimization rules based on real-world performance data can help in exploring a wider range of optimization possibilities.

How could the rule-driven rewrite framework be integrated with automated tools to enable end-to-end optimization of distributed systems?

Integrating the rule-driven rewrite framework with automated tools can significantly enhance the optimization process for distributed systems. One approach could involve developing a tool that analyzes the protocol's Dedalus code, identifies potential optimization opportunities based on predefined rules, and automatically applies the necessary rewrites to the code. This tool could leverage static code analysis techniques to detect patterns and dependencies within the protocol logic, enabling it to generate optimized versions of the protocol automatically. Additionally, incorporating machine learning algorithms to learn from past optimization successes and failures could further enhance the tool's capabilities. By automating the optimization process, the tool can streamline the deployment of efficient distributed protocols and adapt to changing system requirements in real-time.