XA support for Microservices

Question

Scenario: I have multiple XA compliant databases fronted by different microservices which perform CRUD operations on them. I need to perform a 2 phase commit among these microservices. This means that I have a server running which makes API calls into these microservices to do some update, and these updates should be transactional. We are planning to create a transaction manager to manage this.

Question: All the available solutions like Atomikos etc. mandate the different transactions to happen on the same server but in my case these happen in different microservices. How can we provide transaction management in this case? Ultimately we wanted to prepare transactions and then commit them in a different session as managed by our own transaction manager. Is that possible?

Answer 1

I don't think you mean a different Session exactly, but one Application tier level transaction where application components one different server are inside the transaction boundary.

The issue that you are facing is that those who created Microservices were not aware or experienced enough with information systems to understand these scenarios.

Microservices are essentially a false generalization and derivative of a stereotyping

Transactions and many other basic concepts that historically allow Enterprise information systems to exchange information globally without proprietary vendor locking are simply not part of the Microservices understanding.

So your question is really how do you retrofit the architecture concept to do normal day-to-day computer stuff.

In the end, if you keep solving those problems, you will be back to a Java EE application server. (Spring went through the same failings and just ended up wrapping and rebranding Java EE standard functions but with more obnoxious rhetoric)

My business logic on Glassfish can talk to the business login on WebLogic and the CICS tx on the mainframe, and everyone's databases and message queues all on different servers in one transaction. The XA spec lays out how to do this.

Answer 2

It is definitely possible (you can do xa_prepare and xa_commit on separate sessions on most, if not all by now, resource managers) but indeed in the end you will end up writing essentially a Java EE (JTA) style transaction manager with transaction context propagation over REST or messaging or whatever communication mechanism you are using. This has been done eg in Rest-AT specification that Narayana/JBoss implemented and a few others.

Weblogic has an operator with a number of years on it now that takes it into the Kubernetes space and so XA/2PC can simply continue to be used there and Tuxedo will be putting out a product to achieve the same end (over Rest).

The saga pattern should also definitely be considered. It is not to be blindly accepted nor dismissed out of hand as a great pattern/fit in the microservices space. Use cases in transaction management, like any other area, continue to be more and more optimized and specialized and so the fact that it involves eventual consistency, compensation, etc. should not be non-starter in and of itself as it has a number of significant advantages as far as deployment models, scaling, and, to your point, the removal of XA distributed locks, etc. The best solution depends on the specific use case and it's requirements.

A number of the microservices frameworks, such as Narayana (WildFly/Quarkus/SpringBoot), Helidon, and even inside the Oracle DB itself, have Saga engines now. Full disclosure, I work at Oracle and am putting out a workshop on this very product in the next few weeks which will build on the existing "Simplifying Microservices with converged Oracle Database Workshop" which has a very basic choreography-based saga (as opposed to the orchestration-based products/engines I mentioned).

Very happy to talk more on this topic as I've spent the last 25 years writing transaction managers. :)

Answer 3

For the scenario described in the question, you should try using Oracle Transaction Manager for Microservices (MicroTx). It is a free product that comes with a transaction manager and client library for microservices written in Java and node.js. With this, you can create XA transactions involving multiple microservices. Oracle MicroTx - https://www.oracle.com/database/transaction-manager-for-microservices