Repro for CAM-12114
What happens here
The repository contains a minimal Spring Boot project with Camunda BPM, where the data source for Camunda is separate from the primary data source. Both data sources are wrapped to log a message every time when a connection is obtained.
With the default data source auto-configuration in Camunda Spring Boot starter,
Camunda opens unneeded connections to the application data source.
It can be seen in the logs: the message Getting connection from HikariPool-Application
is logged even though no one uses the primary data source.
This happens because Camunda's DefaultDatasourceConfiguration uses the default
PlatformTransactionManager bean (which by default is DataSourceTransactionManager
using the primary data source) even if the data sources are different.
A dirty fix is available in FixedCamundaDataSourceConfiguration:
the transaction manager is replaced by one with correct data source.
If the @Component line in the file is uncommented, there are no more log messages
indicating connection to the application data source.
How to run
The start.sh script will start two databases using docker-compose, and then
compile and run the application with Gradle.
When the application starts, it exposes an endpoint at http://localhost:8080/test
which executes a simple query using Camunda's RuntimeService; this endpoint can be
used to observe the incorrect behaviour.