I’ve been interested in the concepts of event sourcing for several years, and am taking a serious look at it again. I’m frankly a bit dismayed at what I’m seeing on google. On the first results page I’ve found a blog post that refers to event sourcing, and misuses the term. I’m hoping that there’s a translation issue here, as it’s a very well put together post. I suspect French may be the writers primary language. I also don’t have any fundamental issues with the architecture they describe in the post. I’m currently using something very similar, but it isn’t “event sourcing,” it’s Pub-Sub. While you are “Sourcing” events to a subscriber, this has nothing to do with event sourcing, and is already a well established messaging pattern.

We all misuse terms from time to time (I’m a big offender), and as our industry is constantly evolving it can be difficult to keep up with every new term out there. However; if you are going to use a term such as event sourcing in the title of a public post, please do just a bit of research before publishing. A quick internet search would have not only shown the mistake, but also introduced them to a new architectural pattern. I’m not trying to trash the author, hence I am not including a link. Rather I’m speaking of it here, more as a way to keep my self honest. As I said, I’m a big offender.

For those who don’t know what I’m going on about, event sourcing stores system data as a series of events in the order they occurred. While in some cases an aggregate object is created from these events, the events themselves are always maintained in an event store. Aggregate objects can be destroyed and then recreated by reading, or playing forward, the events in the event store. This allows you to recreate an object as it was at any period in it’s lifetime. The basic concept is similar to a source control system, where you can see the entire history of a files check-ins, and revert back to a specific period in time. Event sourcing is closely related to Domain Driven Design (DDD), and you will likely hear people refer to using the events to derive system state, as opposed to a specific objects data model.