[odb-users] any significant changes to threading model in 2.5?

[NIkolai Marchenko]

Correct me if I am wrong: I was of the opinion that generating a new
database object didn't do anything to an internal thread_local connection
held by an odb::transaction instance . This was a basis of what I was doing
in my code and it worked fine previously.

In fact there are two distinct paths that are now causing issues that
worked in 2.4:

1) Loading an internal lazy object in a separate thread via .load()
compared to where the original outside lazy object was acquired
2) Trying to persist an object in an odbcallbackhook that creates a new
database object, but still uses the same odb::transaction, since, inside my
framework, when it sees that a thread_local odb::transaction is already
loaded it doesn't try to open a new transaction, but still creates a new
odb::database..

It's possible that both of those were mishandling of the library on my side
that were never checked, but they have been working flawlessly for 2 years
so now I am left scratching my head about what would be a correct path of
dealing with it.

On Tue, Feb 18, 2025 at 12:37 PM Boris Kolpackov <boris at codesynthesis.com>
wrote:

> NIkolai Marchenko <enmarantispam at gmail.com> writes:
>
> > I am getting this error:
> >
> >
> /home/zeks/odbbuild/libodb-gcc-9/libodb-gcc-9/libodb-2.5.0/odb/transaction.cxx:340:
> > virtual odb::connection&
> > odb::transaction_impl::connection(odb::transaction_impl::database_type*):
> > Assertion `db == 0 || db == &database_' failed.
>
> This is a "sanity check" that makes sure you don't use a transaction that
> was started on a different database instance. This check is actually new
> in 2.5.0, I see it's not present in 2.4.0. So maybe it is catching an
> error on your side?
>
> The only significant threading-related change in ODB 2.5.0 is that we
> have switched to C++11 threads. In ODB 2.4.0 we used POSIX threads on
> POSIX and Win32 threads on Windows. But I don't think this should matter,
> even if you are using the POSIX API for TLS.
>
>
> > This happens modestly in thread workers, my code is keeping thread_local
> > instance of odb::transaction obtained with db->begin().
>
> It would be interesting to see if database_ points to a valid database
> instance.
>