Book Image

Clojure High Performance Programming

By : Shantanu Kumar
Book Image

Clojure High Performance Programming

By: Shantanu Kumar

Overview of this book

<p>Clojure is a young, dynamic, functional programming language that runs on the Java Virtual Machine. It is built with performance, pragmatism, and simplicity in mind. Like most general purpose languages, Clojure’s features have different performance characteristics that one should know in order to write high performance code.<br /><br />Clojure High Performance Programming is a practical, to-the-point guide that shows you how to evaluate the performance implications of different Clojure abstractions, learn about their underpinnings, and apply the right approach for optimum performance in real-world programs.<br /><br />This book discusses the Clojure language in the light of performance factors that you can exploit in your own code.</p> <p>You will also learn about hardware and JVM internals that also impact Clojure’s performance. Key features include performance vocabulary, performance analysis, optimization techniques, and how to apply these to your programs. You will also find detailed information on Clojure's concurrency, state-management, and parallelization primitives.</p> <p>This book is your key to writing high performance Clojure code using the right abstraction, in the right place, using the right technique.</p>
Table of Contents (15 chapters)
Clojure High Performance Programming
Credits
About the Author
Acknowledgments
About the Reviewers
www.PacktPub.com
Preface
Index

Applying back pressure


We discussed back pressure briefly in the previous chapter. Without back pressure, we cannot build a reasonable load-tolerant system with predictable stability and performance. In this section, we will look at how to apply back pressure in different scenarios in an application. At a fundamental level, we should have a threshold of the maximum number of concurrent jobs in the system, and based on that threshold, we should reject new requests above a certain arrival rate. The rejected messages may either be retried by the client or ignored if there is no control over the client. When applying back pressure to user-facing services, it may be useful to detect system load and at first deny auxiliary services in order to conserve capacity and degrade gracefully in the face of high load.

Thread pool queues

JVM thread pools are backed by a queue, which means that when we submit a job into a thread pool that already has the maximum number of jobs running, the new job lands in...