FBPooledConnection in some kind of loop

[Fabio Luis - Vanguarda TI]

Hi.

I have two servers, one with firebird 5.0.3 and another with many docker containers running Payara application server using jaybird 5.0.9.java8.

In some situations could be network instabilities between servers, or even a Firebird restart.

And when this happens, at least one docker container has problems with FBPooledConnection in some kind of loop.

The loop only stops when I restart the container (Payara application server).

Attached some images from the profiler can be more helpful to understand the problem.

Thanks

Fabio Silva

[Mark Rotteveel]

I think the culprit is that `currentException = ex.getNextException();`
That should be `currentException = currentException.getNextException();`

It ends up in an infinite loop if `ex` actually has a next exception and
neither ex or that next exception are fatal. That code has been that way
at least since 2016, so I'm surprised no one has been bitten by that
earlier.

As a workaround, consider using org.firebirdsql.ds.FBSimpleDataSource
(Resource Type: javax.sql.DataSource) instead in that configuration.

I'll create a ticket and fix this.

Mark
--
Mark Rotteveel

[Mark Rotteveel]

On 06-03-2026 13:01, 'Mark Rotteveel' via firebird-java wrote:
> As a workaround, consider using org.firebirdsql.ds.FBSimpleDataSource
> (Resource Type: javax.sql.DataSource) instead in that configuration.
>
> I'll create a ticket and fix this.

I created https://github.com/FirebirdSQL/jaybird/issues/927

Mark
--
Mark Rotteveel

[Fabio Luis - Vanguarda TI]

Hi Mark,

This behavior has been happening for a few years now, but since it's extremely sporadic, I'd never been able to reproduce it.

Yesterday I was profiling an application and by coincidence the problem occurred and I was able to capture it.

> As a workaround, consider using org.firebirdsql.ds.FBSimpleDataSource
> (Resource Type: javax.sql.DataSource) instead in that configuration.

I currently use a JDBC connection pool on the Payara application server.

I'm not familiar with the difference between FBSimpleDataSource and FBConnectionPoolDataSource in a connection pool. Could you please point out what I would be gaining (or losing) with this change? And does FBSimpleDataSource work with JDBC connection pools?

> I'll create a ticket and fix this.

Could you share the link so I can follow along, please?

Kind Regards

Fabio Silva

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[Mark Rotteveel]

On 06-03-2026 14:22, Fabio Luis - Vanguarda TI wrote:
> > As a workaround, consider using org.firebirdsql.ds.FBSimpleDataSource
> > (Resource Type: javax.sql.DataSource) instead in that configuration.
>
> I currently use a JDBC connection pool on the Payara application server.
>
> I'm not familiar with the difference between FBSimpleDataSource and
> FBConnectionPoolDataSource in a connection pool. Could you please point
> out what I would be gaining (or losing) with this change? And does
> FBSimpleDataSource work with JDBC connection pools?

It will work. Instead of Jaybird providing the PooledConnection
implementation, Payara itself will provide the equivalent of that to
wrap the physical connection returned by the data source. In fact,
Payara's documentation doesn't even mention
javax.sql.ConnectionPoolDataSource, so it might even be better to switch
to using FBSimpleDataSource anyway. Don't switch to FBXADataSource (a
javax.sql.XADataSource), as that has the same flaw, and if you don't use
distributed transactions, you don't need it.

It shouldn't make much difference, except that you'll rely on what
Payara considers fatal exceptions to invalidate connections, instead of
Jaybird. That could result in connections sometimes being invalidated
when they could be reused. However, given Jaybird itself will usually
close the physical connection on fatal errors anyway, that shouldn't
matter much in practice.

That said, I haven't used Payara myself, so you will want to verify that
for yourself.

> > I'll create a ticket and fix this.
>
> Could you share the link so I can follow along, please?

I posted that in a later message:

[Fabio Luis - Vanguarda TI]

Thanks a lot ;-)

Fabio Silva

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[Mark Rotteveel]

Fix has been committed. I expect to release Jaybird 5.0.12 and Jaybird
6.0.5 by the end of this month. Currently, some changes for JDBC 4.5
support are pending, and as Java 26 will be released later this month,
I'd prefer if those changes landed in these versions as well.

Mark
--
Mark Rotteveel

[Fabio Luis - Vanguarda TI]

Awesome!

Thanks

Fabio Silva

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