Paper Reading: Ray: A Distributed Framework for Emerging AI Applications

Paper link: https://www.usenix.org/system/files/osdi18-moritz.pdf

Overview

Ray is a new and grossing distributed programming framework, with an ambitious plan to be the foundation of emerging AI/ML applications. In its own words, it aims to “provide a universal API for distributed computing”. Which means it needs to provide a programming interface that’s flexible enough for new applications, and a backend system designed to scale for elastic computing needs with some good performance. This paper (OSDI 18’) explains its API and architecture design to fulfill this goal. And I’ve found some very interesting points.

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Paper Reading: 150 Successful Machine Learning Models Deployed: 6 Lessons Learned At Booking.com

Paper link: https://www.kdd.org/kdd2019/accepted-papers/view/150-successful-machine-learning-models-6-lessons-learned-at-booking.com

Or download.

First published in KDD from booking.com, the paper described its lessons from deploying Machine Learning models in their production service. It provided some intriguing insights. I believe many are very valuable to understanding applying Machine Learning in real-world scenarios.

Here are some of my takeaways.

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Paper Reading: Julia: Dynamism and Performance Reconciled by Design

Link: https://dl.acm.org/doi/pdf/10.1145/3276490

The paper outlines the Julia programming language’s some most important design choices, and explains how they build a bridge between user-friendliness and performance.

The paper provided with a few benchmarks, to compare its performance with a C baseline, along with other dynamic languages like Python, MATLAB, JavaScript, and so on. While other dynamic programming languages suffer great performance loss, due to its dynamism, Julia can compete relatively close with the C/C++ baseline, with up to native performance in a few cases, most of the benchmarks are within 2x of C or C++, while Python can suffer more than 70x slower performance than C++.

This is significant, as it may eliminate the “prototype in dynamic language, then reimplement in static language for faster performance” cycle, eliminating extra time on coding to achieve efficiency without sacrificing much performance.

Some key takeouts from this paper:

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Paper Reading: Aurora: Distributed Relational Database

The following is my overly simplified summary of paper reading.

Aurora is a geo-distributed SQL database that supports replication, high-availability, and transactions, with its distributed design around replicating the database WAL log.

References

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Reading: Cassandra Data Modeling

Reading from Cassandra official website: https://www.datastax.com/sites/default/files/content/whitepaper/files/2019-10/CM2019236 - Data Modeling in Apache Cassandra ™ White Paper-4.pdf

Cassandra is a exemplary implmentation of NoSQL database, and gained popularity in various web, big data, and ML applications. Recently I’ve stumbled upon a good summary of Cassandra handbook, which includes a decent introduction to its data modeling techniques, which can in term be used in other NoSQL databases.

Here are my notes and summaries:

Data Modeling Concepts

There are great many ways Cassandra and traditional RDBMS are different: Cassandra is a wide-column database, with BASE eventual consistency guarantees, has looser relationships between tables. Therefore one needs to model their data very differently than traditional RDBMS for the application to run efficiently.

Namely NoSQL has following differences:

  • No Joins: tables have loose relationships with each other without database level joining.
  • No Referential Integrity: RDBMS requires foreign keys to refer to primary key in another table. NoSQL doesn’t enforce this.
  • Denormalization: contrary to what RDBMS normalization techniques, denormalization is first-class citizen in NoSQL. Many NoSQL databases supports aggregating fields in the same table to achieve row level atomicity.
  • Query First: SQL data modeling starts with entities and relations, while NoSQL data modeling starts with application queries.
  • Sorting: Sorting is an important design decision, for Cassandra and many NoSQL databases.

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Blog Reading: The log - What every software engineer should know about real-time data's unifying abstraction

Link: https://engineering.linkedin.com/distributed-systems/log-what-every-software-engineer-should-know-about-real-time-datas-unifying

Kafka is a message queue, a pub-sub system, an event sourcing tool, and a stream processing infrastructure, is a key part of many streaming distributed systems that requires streaming data. Its underlying idea, is to aggregate data from a distributed sources, to a unifying linear log structure.

The blog is from Kafka’s creator Jay Kreps when he was at LinkedIn, contemplating the log abstraction as a key part of any distributed systems. This is not Kafka’s design paper, implementation or a tutorial, but rather the process of brewing the idea that led to its birth, and I found it equally interesting. The following are my notes.

The link to Kafka paper: https://www.semanticscholar.org/paper/Kafka-%3A-a-Distributed-Messaging-System-for-Log-Kreps/9f948448e7a5f0cc94cd53656410face8b31b18a

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Paper Reading: Mesos: A Platform for Fine-Grained Resource Sharing in the Data Center

Link to paper: https://people.eecs.berkeley.edu/~alig/papers/mesos.pdf

Presentation: https://www.usenix.org/conference/nsdi11/mesos-platform-fine-grained-resource-sharing-data-center

Mesos is a cluster resource management software from UC Berkeley. Unlike many other frameworks already existed, Mesos is designed to support heterogeneous frameworks (Hadoop, MPI, etc) in the same cluster and share resources between them, by providing a thin layer that making resource offers to the framework schedulers, and delegate the scheduling decision to the frameworks themselves.

With this design, Mesos can achieve pretty good elasticity between frameworks, and letting frameworks choose their own resources results in better data locality.

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