> On Nov 16, 2025, at 3:52 AM, Graham Leggett <[email protected]> wrote:
>
> Hi all,
>
> I have a tomcat9 web application that is leaking connections, and I need to
> detect where the leaks are occurring. This is surprisingly difficult.
>
> The leak is reproducible, and occurs in a controlled test environment, so the
> vast majority of advice out there about monitoring database connections isn't
> useful - I know there is a leak. The codebase is large, so the "look at the
> codebase" advice doesn't work.
>
> The exceptions I get tell me all about the straw that broke the camel's back,
> but none of that is useful - what I need to know at that point is what else
> is on the camel's back.
>
> Is there a mechanism that exists where you can trigger a dump of the stack
> traces of all database connections currently open and where they were opened?
> Remember - in my case this is a reproducible leak in a controlled test
> environment, so I don't have the problem of a live system or filtering out
> noise.
>
> This isn't working for me, I see no stack traces related to abandoned
> connections:
>
> <Resource auth="Container" driverClassName="org.postgresql.Driver"
> factory="org.apache.tomcat.dbcp.dbcp2.BasicDataSourceFactory"
> logAbandoned="true" maxIdle="5" maxTotal="5" maxWaitMillis="10000" name=""
> password="" type="javax.sql.DataSource" url="" username=""
> removeAbandonedOnBorrow="true" removeAbandoned="true"
> removeAbandonedTimeout="10" />
>
> Is there a breakpoint I can stop the code at, or a signal I can send?
>
So the code base is opening connections and not closing them. Assuming this is
a java environment you might need to wrap every connection call in a
“try-with-resource” block to get a guaranteed close.
Can you narrow your tests to find the culprit(s)?
> Regards,
> Graham
> --
>
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