Architecting your Concurrency Model
By Patrick Leonard, VP Engineering & Product Strategy
Abstraction of concurrency from software application logic
(a.k.a: “I feel the need… the need for - Concurrency…”)
From Monolith to Component Architectures
In the olden days of computing, everything was combined into a single lump of software - including operating system functions, application logic, data, user presentation. After some time, we realized that creating a separation between the hardware and the software application would be useful, and the operating system was born. Some time later, we realized that managing the data was a distinct task, and databases became a separate entity. Some time after that, we decided that it would be a good idea to split out the user interface, and the era of client/server began.
So it went, the software industry continued to evolve our architectures into more componentized and modular arrangements.
Architecting for Concurrent Computing
Now that multi-core architectures are common and the need for concurrency in software architectures well understood, the next question is how best to architect our applications and how best to structure development organizations to support them. For the moment, let’s talk about the development organization. In the past, concurrency was a task limited to edge cases, but now ubiquitous multi-core hardware is making it much more common.
There are two ways to handle this. First, train all your software developers to be experts in concurrency (yikes…). Second, have concurrency specialists to focus on making your applications parallel. Since training all of your software developers to be experts in concurrency seems daunting, it would seem that the second option is better. But if concurrency is now required through significant portion of your application architecture, how can only a few engineers or architects be responsible for it?
The answer lies in abstracting the concurrency model from the application logic. While this may not be possible for all aspects of your concurrency model, it certainly should be for some - especially for well-defined services (in the SOA definition of the word). Services can be run in multiple instances across multiple threads and multiple cores (even multiple servers) to achieve a significant degree of concurrency without rewriting the code inside the service.
To the extent that you can do this, you can allow your application developers to focus on application logic and your concurrency experts to focus on concurrency. In addition, you can gain quite a bit more flexibility to your application architecture. The more your concurrency is abstracted, the easier it is to change without affecting the application logic. It’s really just an extension of the idea of loose coupling.
The Concurrency Model
This means that the application developer does not have to be the primary owner of the concurrency model. The application developer is able to focus on the application, and a concurrency expert can design about the concurrency model, just as a DBA does with the data model - I wouldn’t be surprised if we start to see something like a Concurrency Model Architect (CMA?).
Anyway, the whole thing relies on being able to separate your concurrency model from your application logic. More on that later.
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