The Saga Continues: "Queues Are Databases?"

Udi had a couple of comments regarding my second post on Queues Are Databases.

The first thing Udi said was:

"I don't like the term "Saga". I prefer a term that reflects a different perspective: Long-running workflow."

I think both terms have their place. In my upcoming SOA Patterns book I talk about a "Workflodize" pattern which is a service structural pattern; i.e. you add a workflow to a service to get benefits such as Udi describes.

However, there's also a Saga pattern which is service interaction pattern. The Workflodize pattern is a good option to support Sagas within each of the involved parties.

The second point Udi made was that the messages from any of the sources invovled should have low-coupling between them. (That is, if I send message A and message B it wouldn't matter if you recieve A and then B or B and then A).

I agree that it is preferable to model your message like this, however it is:

• Not always possible or it might not make sense
• You don't always control all the services involved in the saga

So, Udi, this is what I have to say to that. Now what :)?

Posted by Arnon Rotem-Gal-Oz at 06:11 AM  Permalink