OOM error on Comdb2 JDBC driver

[hgeraldino]

Describe the bug
Each Comdb2Connection has an internal Comdb2Handle that is reused across all statements for the given connection. Because of this, there's a potential for the internal List<String> set commands that is used to keep track of the set commands to grow unbounded and cause OOM errors. This is not a theoretical problem: we've encountered this issue when running the latest 2.6.0 version of the JDBC driver.

To Reproduce
Steps to reproduce the behavior:
Please refer to the https://github.com/hgeraldino/comdb2-oom-example repository, which has a sample Integration Test that can be used to reproduce the problem.

Expected behavior
Each java.sql.Statement should only care about the set SQL statements of its own.

Screenshots
The referenced project has a Screenshot of a heap dump taken from one of our running applications. It shows the enormous number of String references kept by the Comdb2Handle .

Environment (please complete the following information):

• Operating System and Version:

$ uname -a
Linux <hostname> 3.10.0-1160.80.1.el7.x86_64 #1 SMP Sat Oct 8 18:13:21 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
$ java -version
openjdk version "17.0.6" 2023-01-17
OpenJDK Runtime Environment Temurin-17.0.6+10 (build 17.0.6+10)
OpenJDK 64-Bit Server VM Temurin-17.0.6+10 (build 17.0.6+10, mixed mode, sharing)

[Brunosampaiomartins]

SQL Error: Internal jdbc driver error
Internal jdbc driver error
Internal jdbc driver error
Java heap space
Java heap space

Alguém sabe pq esse erro?

[hgeraldino]

SQL Error: Internal jdbc driver error Internal jdbc driver error Internal jdbc driver error Java heap space Java heap space

Alguém sabe pq esse erro?

Might be related, but it's hard to tell without a heap dump. I'd suggest taking a heap dump and examining its contents in order to pinpoint the cause