Atul S. Khot - Concurrent Patterns and Best Practices

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Atul S. Khot is a self-taught programmer and has written software programmes in C and C++. Having extensively programmed in Java and dabbled in multiple languages, these days, he is increasingly getting hooked on Scala, Clojure, and Erlang. Atul is a frequent speaker at software conferences and a past Dr. Dobb's product award judge. He was the author of Scala Functional Programming Patterns and Learning Functional Data Structures and Algorithms, published by Packt Publishing.

Anubhava Srivastava is a Lead Engineer Architect with more than 22 years of systems engineering and IT architecture experience. He has authored the book Java 9 Regular Expressions published by Packt Publishing. He's an active contributor to Stackoverflow and figures in its top 0.5% overall reputation. As an open source evangelist he actively contributes to various open source development and some popular computer programming Q&A sites like Stack Overflow with a reputation/score of more than 170k.

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Thank you for purchasing this book! We live in a concurrent world and concurrent programming is an increasingly valuable skill.

I still remember the Aha! moment when I understood how UNIX shell pipeline works. I fell headlong in love with Linux and the command line and tried out many combination filters (a filter is a program reading from standard input and writes to standard output) connected via pipes. I was amazed by the creativity and power brought about by the command line. I was working with concurrent programs.

Then, there was a change of project and I was thrown headlong into writing code using the multithreaded paradigm. The language was C or C++, which I loved deeply; however, to my surprise I found that it was a herculean effort to maintain a legacy code base, written in C/C++ that was multithreaded. The shared state was managed in a haphazard way and a small mistake could throw us into a debugging nightmare!

Around that time, I came to know about object oriented (OO) design patterns and some multithreaded patterns as well. For example, we wanted to expose a big in-memory data structure safely to many threads. I had read about the Readers/Writer lock pattern, which used smart pointers (a C++ idiom) and coded a solution based on it.

Voila! It just worked. The concurrency bugs simply disappeared! Furthermore, the pattern made it very easy to reason about threads. In our case, a writer thread needed infrequent but exclusive access to the shared data structure. The reader threads just used the structure as an immutable entityand look mom, no locks!

No locks! Well, well, well... this was something new! As the locks disappeared, so did any possibility of deadlocks, races, and starvation! It felt just great!

There was a lesson I learned here! Keep learning about design patterns and try to think about the design problem at hand - in terms of patterns. This also helped me reason better about the code! Finally, I had an inkling of how to tame the concurrency beast!

Design patterns are reusable design solutions for common design problems. The design solutions are design patterns. Your problem domain may vary, that is, the business logic you need to write will be applicable to solving the business problem at hand. However, once you apply the pattern, things just fall in place, more or less!

For example, when we code using the OO paradigm, we use the Gang Of Four (GOF)