Sunday, March 04, 2012

Review: Service Design Patterns


This is the review I posted to Amazon on the book Service Design Patterns:

This book discusses many of already commonly used patterns in the industry concerning web services. Each pattern has code examples, and the nicest part is the very reasonable "Considerations" part, which has a list of items to consider before using any of the patterns.

However, if you have been working with web services for some years and have kept up with the changes and trends, this book will not necessarily learn much from this book. It's not a long book, so it may be worth your time reading it to fill any gaps in your understanding of web services. For anyone new to web services, though, this is a must read to understand the common patterns before moving on with any trendy way of doing things.

Also, this book is an attempt to formalize many of the patterns that the industry already follows - at least I've seen many companies following them in a way or another. It is good that we all have the same terminology, but on the other hand, it doesn't really get into a lot of details of each pattern, so the the reader needs to research further if s/he wants to deepen his/her knowledge. For each of these patterns - just like in a recipes book - the author gives an example (either in Java or C#) and he was able to keep them short enough but focused on the patterns he wants to show.

From my own experience, these are some patterns or areas I'd include in the book to make it more complete:
- Client-service interaction: long polling. Other than a regular Request/Response, nowadays you see services with long polling, which can be a quite important pattern to use depending on your use case. This pattern has been out for so many years that I surprised not to see it in this book.
- Service Interceptors: this is a really important and probably can be a book of its own, but I'd love to see more patterns on how certain things like exception handling and validation could be done and pros/cons of each approach. Oftentimes these are areas that many service developers get wrong and having patterns here would help steer them into the right direction (rather than realizing later the mistake). The author touches briefly on them from a high level, but there are different ways of the doing the same thing, and it deserved a little more attention in my opinion.
- Operation concerns: typically if one has a service, it tends to be a system that is supposed to be highly available, so service developers want to minimize downtime. For that, you must have a "devops" mindset to know where to put the right logging, where to log metrics for performance, in what places to log errors, how to handle log files. There are so many pieces of advice around operations - but unfortunately I did not find a book on them yet, so developers still need to learn from practice.

Last but not least, note that this book doesn't talk service architecture. It doesn't get into details of how to architect the service, including scalability, reliability, etc. You would need to find other option for that.
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