Past Meetup

Pat Helland on "Immutability Changes Everything"

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180 people went

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**Please note that this month's location is not optimal for ADA. Please let us know your needs and we will do our best to accommodate you.


Daniel "Spoons" Spoonhower on "A Unified Theory of Garbage Collection"

Let's take a deep dive into language implementation: garbage collectors are a great tool for improving programmer productivity… until something goes wrong and you find yourself endlessly tuning collector configuration parameters. This paper takes a principled approach to understanding different garbage collection algorithms and offers something useful for both language implementors and programmers that use garbage-collected languages.

Spoon's Bio

Spoons is a co-founder at LightStep, a company that makes complex microservice applications more transparent and reliable. An expert in distributed tracing, he is the contributor to the OpenTracing standard which is a Linux Foundation project. Previously, Spoons spent almost six years at Google where he ate lots of snacks and worked as a Staff Software Engineer on various products, including Google’s infrastructure and Cloud Platform teams. Spoons holds a PhD from Carnegie Mellon University in Computer Science.

Main Talk

Pat Helland on "Immutability Changes Everything"

There is an inexorable trend toward storing and sending immutable data. We need immutability to coordinate at a distance, and we can afford immutability as storage gets cheaper. This article is an amuse-bouche sampling the repeated patterns of computing that leverage immutability. Climbing up and down the compute stack really does yield a sense of déjà vu all over again.

It wasn’t that long ago that computation was expensive, disk storage was expensive, DRAM (dynamic random access memory) was expensive, but coordination with latches was cheap. Now all these have changed using cheap computation (with many-core), cheap commodity disks, and cheap DRAM and SSDs (solid-state drives), while coordination with latches has become harder because latch latency loses lots of instruction opportunities. Keeping immutable copies of lots of data is now affordable, and one payoff is reduced coordination challenges.

Pat's Bio

Pat Helland ( has been working in distributed systems, databases, transaction processing, scalable systems, and fault tolerance since 1978. For most of the 1980s, Pat worked at Tandem Computers as the Chief Architect for TMF (Transaction Monitoring Facility), the transaction and recovery engine under NonStop SQL. After 3+ years designing a Cache Coherent Non-Uniform Memory Multiprocessor for HaL Computers (a subsidiary of Fujitsu), Pat moved to the Seattle area to work at Microsoft in 1994. There he was the architect for Microsoft Transaction Server, Distributed Transaction Coordinator, and a high performance messaging system called SQL Service Broker, which ships with SQL Server. From[masked], he was at Amazon working on the product catalog and other distributed systems projects including contributing to the original design for Dynamo. After returning to Microsoft in 2007, Pat worked on a number of projects including Cosmos, the scalable “Big Data” plumbing behind Bing. While working on Cosmos, Pat architected both a project to integrate database techniques into the massively parallel computations as well as a very high-throughput event processing engine. Since early 2012, Pat has worked at in San Francisco. He is focusing on multi-tenanted database systems, scalable reliable infrastructure for storage, and software defined networking.