Book Image

ZeroMQ

By : Faruk Akgul
Book Image

ZeroMQ

By: Faruk Akgul

Overview of this book

<p>ØMQ (also spelled ZeroMQ, 0MQ, or ZMQ) is a high-performance asynchronous messaging library aimed at use in scalable distributed or concurrent applications. It provides a message queue, but unlike message-oriented middleware, a ØMQ system can run without a dedicated message broker. The library is designed to have a familiar socket-style API.<br /><br />"ZeroMQ" teaches you to use ZeroMQ through examples in C programming language. You will learn how to use fundamental patterns of message/queuing with a step-by-step tutorial approach and how to apply them. Then, you’ll learn how to use high level APIs and to work with multiple sockets and multithreaded programs through many examples.<br /><br />This book looks at how message/queue works in general and what kinds of problems it solves. Then, it explains how ZeroMQ works and how it differs from other message/queue libraries and how it can be used in different scenarios.<br /><br />You will also learn how to apply essential message/queue design patterns in different scenarios, and how they differ from each other. It shows you practical examples you can apply. You will also learn how to work with multiple sockets.<br /><br />You will learn the basics of ZeroMQ as well as how to use different patterns.</p>

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ZeroMQ
Faruk Akgul
Mar, 2013 | 108 pages
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Table of Contents (12 chapters)
ZeroMQ
ZeroMQ
Credits
Credits
About the Author
About the Author
About the Reviewers
About the Reviewers
www.PacktPub.com
www.PacktPub.com
Preface
Preface
Free Chapter
1
Getting Started
Getting Started
The beginning
The message queue
Introduction to ZeroMQ
Hello world
Handling strings in C
Checking the ZeroMQ version
Summary
2
Introduction to Sockets
Introduction to Sockets
The publish-subscribe pattern
The pipeline pattern
Getting ZeroMQ context
Destroying ZeroMQ context
Cleaning up
Detecting memory leaks
Summary
3
Using Socket Topology
Using Socket Topology
What a socket is
Types of Internet sockets
Transmission Control Protocol (TCP)
TCP header
ZeroMQ sockets
Routing schemes
Working with multiple sockets
Working with multi-part messages
How to handle interruptions
Introduction to CZMQ
Summary
4
Advanced Patterns
Advanced Patterns
Extending the request-reply pattern
Writing multithreaded applications with ZeroMQ
Wrapping publisher-subscriber messages
High watermark
Reliability
Summary
Appendix
Appendix
Index
Index

How to handle interruptions

You need to close the applications properly when you interrupt your application with signals such as SIGTERM or SIGINT. SIGTERM is one of the POSIX signals that sends a signal to a process to end it. Signals are asynchronous and are vulnerable to race conditions.

  • SIGTERM: When you execute the kill command with its defaults in a Unix system, you are basically calling a SIGTERM signal to the denoted process. These signals should be handled properly so your application can release the resources or close database connections and flush the messages properly.

  • SIGINT: This signal can be caught by the application just like SIGTERM as well. The user usually calls it with Ctrl + C.

  • SIGKILL: This is the signal that is called with a kill -9 command. However, this signal cannot be caught by an application, so there is nothing much we could do about it.

SIGINT could be caught in languages that support exception handling by throwing the proper exception such as KeyboardInterrupt...

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