Sessions at Strange Loop 2011 matching your filters

Clojure has powerful concurrency primitives, but they don’t always play nicely with side-effects. Services that take a single input and produce a single output can be easily modeled as functions, but more complicated relationships between input and output lack a first-class representation in the language.

This talk will explore a potential solution: Lamina, which provides abstractions for event-driven workflows, and Aleph, which uses these abstractions to model network communication over a variety of protocols.

Topics will include:

• A survey of event-driven programming, discussing the benefits and shortcomings of various approaches
• An abstraction that models events as streams of messages, allowing familiar operations such as map, filter, and reduce
• Building upon these streams to create complex asynchronous workflows
• Using these abstractions to create sophisticated, performant network services with minimal boilerplate and ceremony

The last decade the speed of CPU’s has been stagnating because of the inability to dissipate the heat and run them cost efficiently. The number of cores has been increasing steadily to compensate. 10 Years ago having access to a 48-core machine, most developer would consider unimaginable, but for $6000 you can order one on the Dell site today. So multi-core machines are here to stay.

Since more threads are needed to use all these cores, which is a problem in its own, the need to deal with concurrency control, is increasing as well. Traditionally this was the area of locks, semaphores and compare-and-swap instructions. And although they are extremely useful and probably will be for a long time to come, creating larger systems based on these lower concurrency primitives is a very daunting and error-prone task. I guess some of us have had the pleasure of running into race-problems and deadlocks and know how difficult it is to reproduce them.

Software Transactional Memory is a concurrency control mechanism that relies on a higher abstraction and tries to solves a lot of the traditional problems by treating the memory as a database where composition, isolation, consistency and atomicity are provided out of the box. During this presentation the general concepts behind STM are explained as well as some of the fundamental implementation difficulties. And an attempt is made the answer the question of STM is the silver bullet or just a tool in the toolbox.