Distributed XA Transactions in a Spring Boot / Camel Application

Image by Simon Matzinger from Pixabay

In this article, I’ll show how to set up distributed transactions (XA, known also as 2PC) in a Spring Boot / Camel application. Moreover, I’ll describe how to make sure this setup actually works.

What is XA and why do I care?

XA provides an implementation of 2PC (two-phase commit). It’s a distributed transaction architecture supported both by JavaEE platform and by Spring application framework. As opposed to local transactions, it allows to join multiple resources (databases, message brokers etc.) in a single distributed transaction with two distinct phases: prepare and commit.

Without a two-phase commit, handling multiple resources with independent transactions within one operation could lead to inconsistency. For example, if you need to read a message from a queue and write it to the database, one of the following scenarios could happen.

Scenario A, message loss:

• Open transaction for the message broker
• Open transaction for the database
• Read a message from the queue into memory
• Write a message from memory to the database
• Commit message broker transaction (acknowledging the message removes it from the queue)