quarkus.datasource.jdbc.flush-on-close=true causes pool size to exceed max

[shawkins]

Describe the bug

Having this flag set to true and with Agroal version 2.5 we can reproduce this issue also against a normal MSSQL. The max connection pool setting is not considered, and the number of idle connections grow and grow. With Agroal Version 2.3 there is no issue.

See also keycloak/keycloak#39488

Expected behavior

max connections should be honored

Actual behavior

max connections exceeded

How to Reproduce?

No simple reproducer yet.

Was logged initially as keycloak/keycloak#39488

@sschu @binchen-lin may be able to provide something here, or on an upstream agroal issue.

Output of uname -a or ver

No response

Output of java -version

No response

Quarkus version or git rev

3.19

Build tool (ie. output of mvnw --version or gradlew --version)

No response

Additional information

No response

[quarkus-bot]

/cc @barreiro (jdbc)

[sschu]

To add a little information, initially the bug was discovered against MS SQL but later my colleague @binchen-lin found out it also appears under oracle with quarkus.datasource.jdbc.flush-on-close=true. She also still wants to investigate which agroal version this appears in first (2.4 but 2.5) but this was postponed due to higher priorities. Looking at the code changes, this one here looks suspicious because it touches exactly that area: agroal/agroal#109

[geoand]

Also cc @yrodiere for awareness