Clojure High Performance Programming - Second Edition

Table of Contents

Clojure High Performance Programming Second Edition

Credits

About the Author

About the Reviewers

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Free access for Packt account holders

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Errata

Piracy

eBooks, discount offers, and more

Questions

1. Performance by Design

Use case classification

The user-facing software

Computational and data-processing tasks

A CPU bound computation

A memory bound task

A cache bound task

An input/output bound task

Online transaction processing

Online analytical processing

Batch processing

A structured approach to the performance

The performance vocabulary

Latency

Throughput

Bandwidth

Baseline and benchmark

Profiling

Performance optimization

Concurrency and parallelism

Resource utilization

Workload

The latency numbers that every programmer should know

Summary

2. Clojure Abstractions

Non-numeric scalars and interning

Identity, value, and epochal time model

Variables and mutation

Collection types

Persistent data structures

Constructing lesser-used data structures

Complexity guarantee

O(<7) implies near constant time

The concatenation of persistent data structures

Sequences and laziness

Laziness

Laziness in data structure operations

Constructing lazy sequences

Custom chunking

Macros and closures

Transducers

Performance characteristics

Transients

Fast repetition

Performance miscellanea

Disabling assertions in production

Destructuring

Recursion and tail-call optimization (TCO)

Premature end of iteration

Multimethods versus protocols

Inlining

Summary

3. Leaning on Java

Inspecting the equivalent Java source for Clojure code

Creating a new project

Compiling the Clojure sources into Java bytecode

Decompiling the .class files into Java source

Compiling the Clojure source without locals clearing

Numerics, boxing, and primitives

Arrays

Reflection and type hints

An array of primitives

Primitives

Macros and metadata

String concatenation

Miscellaneous

Using array/numeric libraries for efficiency

HipHip

primitive-math

Detecting boxed math

Resorting to Java and native code

Proteus – mutable locals in Clojure

Summary

4. Host Performance

The hardware

Processors

Branch prediction

Instruction scheduling

Threads and cores

Memory systems

Cache

Interconnect

Storage and networking

The Java Virtual Machine

The just-in-time compiler

Memory organization

HotSpot heap and garbage collection

Measuring memory (heap/stack) usage

Determining program workload type

Tackling memory inefficiency

Measuring latency with Criterium

Criterium and Leiningen

Summary

5. Concurrency

Low-level concurrency

Hardware memory barrier (fence) instructions

Java support and the Clojure equivalent

Atomic updates and state

Atomic updates in Java

Clojure's support for atomic updates

Faster writes with atom striping

Asynchronous agents and state

Asynchrony, queueing, and error handling

Why you should use agents

Nesting

Coordinated transactional ref and state

Ref characteristics

Ref history and in-transaction deref operations

Transaction retries and barging

Upping transaction consistency with ensure

Lesser transaction retries with commutative operations

Agents can participate in transactions

Nested transactions

Performance considerations

Dynamic var binding and state

Validating and watching the reference types

Java concurrent data structures

Concurrent maps

Concurrent queues

Clojure support for concurrent queues

Concurrency with threads

JVM support for threads

Thread pools in the JVM

Clojure concurrency support

Future

Promise

Clojure parallelization and the JVM

Moore's law

Amdahl's law

Universal Scalability Law

Clojure support for parallelization

pmap

pcalls

pvalues

Java 7's fork/join framework

Parallelism with reducers

Reducible, reducer function, reduction transformation

Realizing reducible collections

Foldable collections and parallelism

Summary

6. Measuring Performance

Performance measurement and statistics

A tiny statistics terminology primer

Median, first quartile, third quartile

Percentile

Variance and standard deviation

Understanding Criterium output

Guided performance objectives

Performance testing

The test environment

What to test

Measuring latency

Comparative latency measurement

Latency measurement under concurrency

Measuring throughput

Average throughput test

The load, stress, and endurance tests

Performance monitoring

Monitoring through logs

Ring (web) monitoring

Introspection

JVM instrumentation via JMX

Profiling

OS and CPU/cache-level profiling

I/O profiling

Summary

7. Performance Optimization

Project setup

Software versions

Leiningen project.clj configuration

Enable reflection warning

Enable optimized JVM options when benchmarking

Distinguish between initialization and runtime

Identifying performance bottlenecks

Latency bottlenecks in Clojure code

Measure only when it is hot

Garbage collection bottlenecks

Threads waiting at GC safepoint

Using jstat to probe GC details

Inspecting generated bytecode for Clojure source

Throughput bottlenecks

Profiling code with VisualVM

The Monitor tab

The Threads tab

The Sampler tab

Setting the thread name

The Profiler tab

The Visual GC tab

The Alternate profilers

Performance tuning

Tuning Clojure code

CPU/cache bound

Memory bound

Multi-threaded

I/O bound

JVM tuning

Back pressure

Summary

8. Application Performance

Choosing libraries

Making a choice via benchmarks

Web servers

Web routing libraries

Data serialization

JSON serialization

JDBC

Logging

Why SLF4J/LogBack?

The setup

Dependencies

The logback configuration file

Optimization

Data sizing

Reduced serialization

Chunking to reduce memory pressure

Sizing for file/network operations

Sizing for JDBC query results

Resource pooling

JDBC resource pooling

I/O batching and throttling

JDBC batch operations

Batch support at API level

Throttling requests to services

Precomputing and caching

Concurrent pipelines

Distributed pipelines

Applying back pressure

Thread pool queues

Servlet containers such as Tomcat and Jetty

HTTP Kit

Aleph

Performance and queueing theory

Little's law

Performance tuning with respect to Little's law

Summary

Index

Clojure High Performance Programming Second Edition

Clojure High Performance Programming Second Edition

Copyright © 2015 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.

Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

First published: November 2013

Second edition: September 2015

Production reference: 1230915

Published by Packt Publishing Ltd.

Livery Place

35 Livery Street

Birmingham B3 2PB, UK.

ISBN 978-1-78528-364-2

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Credits

Author

Shantanu Kumar

Reviewers

Eduard Bondarenko

Matjaz Gregoric

Commissioning Editor

Nadeem Bagban

Acquisition Editor

Larissa Pinto

Content Development Editor

Divij Kotian

Technical Editor

Anushree Arun Tendulkar

Copy Editor

Yesha Gangani

Project Coordinator

Nikhil Nair

Proofreader

Safis Editing

Indexer

Tejal Soni

Graphics

Abhinash Sahu

Production Coordinator

Manu Joseph

Cover Work

Manu Joseph

About the Author

Shantanu Kumar is a software developer living in Bengaluru, India. He works with Concur Technologies as a principal engineer, building a next-generation stack in Clojure. He started learning computer programming when he was at school, and has dabbled in several programming languages and software technologies. Having used Java for a long time, he discovered Clojure in early 2009 and has been a fan of it ever since.

When not busy with programming or reading up on technical stuff, he enjoys reading non-fiction and cycling around Bengaluru. Shantanu is an active participant in The Bangalore Clojure Users Group, and contributes to several open source Clojure projects on GitHub. He is also the author of the first edition of the book Clojure High Performance Programming, Packt Publishing.

I am grateful to my colleagues, Saju Pillai and Vijay Mathew, at Concur India for imparting marathon performance analysis/tuning sessions. I appreciate the input received from Andy Fingerhut and Zach Tellman on certain topics during the course of writing the second edition of the book. I also want to thank the technical reviewers and the team at Packt for their valuable input and support.

Writing this book has been an arduous task. I want to thank my family for putting up with me while I was immersed in this book for far too many days and weekends. If not for their support, I would not have been able to do justice to the book.

About the Reviewers

Eduard Bondarenko is a software developer living in Kiev, Ukraine. He started programming using Basic on ZXSpectrum a long time ago. Later, he worked professionally in the web development domain.

Eduard used Ruby on Rails for many years. Having used Ruby for a long time, he discovered Clojure in early 2009 and liked the language. Besides Ruby and Clojure, he is also interested in Erlang, Scala languages, machine learning, and logic programming.

Matjaz Gregoric is a software developer living in Ljubljana, Slovenia, with his wife and two children. He has a BS degree in physics, and has been developing software professionally since 2007.

During his career, Matjaz worked on various projects where he was able to get familiar with different technologies and programming languages. In 2010, he got familiar with Clojure and immediately fell in love with it. He is currently working on scalable distributed systems and complex web UIs.

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Preface

Since the first edition of this book was published in November 2013, Clojure has seen a much wider adoption and has witnessed many success stories. The newer versions of Clojure fortify its performance story while staying close to its roots—simplicity and pragmatism. This edition significantly updates the book for Clojure 1.7, and adds a new chapter on the performance measurement.

The Java Virtual Machine plays a huge role in the performance of the Clojure programs. This edition of the book increases the focus on the JVM tools for performance management, and it explores how to use those. This book is updated to use Java 8, though it also highlights the places where features from Java 7 or 8 have been used.

This book is updated mainly to be more of practical use to the readers. I hope that this edition will better equip the readers with performance measurement and profiling tools and with the know-how of analyzing and tuning the performance characteristics of Clojure code.

What this book covers

Chapter 1, Performance by Design, classifies the various use cases with respect to performance, and analyzes how to interpret their performance aspects and needs.

Chapter 2, Clojure Abstractions, is a guided tour of various Clojure data structures, abstractions (persistent data structures, vars, macros, transducers, and so on), and their performance characteristics.

Chapter 3, Leaning on Java, discusses how to enhance performance by using Java interoperability and features from Clojure.

Chapter 4, Host Performance, discusses how the host stack impacts performance. Being a hosted language, Clojure has its performance directly related to the host.

Chapter 5, Concurrency, is an advanced chapter that discusses the concurrency and parallelism features in Clojure and JVM. Concurrency is an increasingly significant way to derive performance.

Chapter 6, Measuring Performance, covers various aspects of performance benchmarks and measuring other factors.

Chapter 7, Performance Optimization, discusses systematic steps that need to be taken in order to identify that the performance bottlenecks obtain good performance.

Chapter 8, Application Performance, discusses building applications for performance. This involves dealing with external subsystems and factors that impact the overall performance.

What you need for this book

You should acquire Java Development Kit version 8 or higher for your operating system to work through all the examples. This book discusses the Oracle HotSpot JVM, so you may want to get Oracle JDK or OpenJDK (or Zulu) if possible. You should also get the latest Leiningen version (2.5.2 as of the time of writing) from http://leiningen.org/, and JD-GUI from http://jd.benow.ca/.

Who this book is for

This book is for intermediate Clojure programmers who are interested in learning how to write high-performance code. If you are an absolute beginner in Clojure, you should learn the basics of the language first, and then come back to this book. You need not be well-versed in performance engineering or Java. However, some prior knowledge of Java would make it much easier to understand the Java-related chapters.

Conventions

In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: Note that identical? in Clojure is the same as == in Java.

A block of code is set as follows:

user=> (identical? foo foo)  ; literals are automatically interned

true

user=> (identical? (String. foo) (String. foo))  ; created string is not interned

false

New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: Clicking the Next button moves you to the next screen.

Note

Warnings or important notes appear in a box like this.

Tip

Tips and tricks appear like this.

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