Dealing with Device Reads Using Akka

You have a device monitor actor. It must poll the device every time an internal expires. When data starts flowing, it flows a lot. Sometimes, however, the device will not have readable data for long periods of time (several seconds), and continuing … [Read more]

DDD with Scala and Akka Revisited

There were a number of issues with the code I wrote in the post Using Scala and Akka with Domain-Driven Design. I am addressing those problems in this post and cleaning up the code. The good thing about revisiting this topic is that you can learn … [Read more]

Using Scala and Akka with Domain-Driven Design

If you've been following my theme for a while I've spent a considerable amount of effort promoting Scala and Akka for use when Implementing Domain-Driven Design. Few seem to share my vision of a completely explicit use of Actors as Aggregates, with … [Read more]

Naming “Shadow” Concepts Across Bounded Contexts

I was asked why the concept named Tenant is used in all three Bounded Contexts for the example code for my book, Implementing Domain-Driven Design. Is it because a Tenant is the exact same thing in all three Contexts? Actually this is a good example … [Read more]

EAI Patterns with Actor Model: Message Channel

After a discussion of all those fancy doodahdah filters, routers, and buses, we are back to the plain old Message Channel. Yes, I did skip the Process Manager. We will get back to it, but for now it seems we all need a bit of boredom. Well, not … [Read more]

EAI Patterns with Actor Model: Message Bus

You have a number of disparate business systems, from purchased commodity applications, to custom developed applications that help achieve competitive advantage, to those of integrating business partners. You need all of these systems to work … [Read more]

EAI Patterns with Actor Model: Message Expiration

If it is possible for a given message to become obsolete or in some way invalid due to a time laps, use a Message Expiration to control the timeout. While we have already dealt with the process timeouts in the Scatter-Gather implementation, this is … [Read more]

EAI Patterns with Actor Model: Claim Check

When you need to break up a composite message into smaller parts, but provide access to any of the parts on demand, use a Claim Check. Consider the Claim Check a unique identifier used to store and access a checked item. You pass as part of a … [Read more]

EAI Patterns with Actor Model: Resequencer

At this point we've covered a number of Message Routers in addition to some less complex, but essential, messaging patterns. With regard to my discussion of Request-Response, Ramesh Mandaleeka asked a few questions about Actor Model and message … [Read more]

EAI Patterns with Actor Model: Scatter-Gather

We've actually already stepped through one implementation of Scatter-Gather. This was the combination of Recipient List and Aggregator, which provides the first of two Scatter-Gather variants. The second variant—that of using a Publish-Subscribe … [Read more]