Add support for Coroutines transactions

[gkdevone]

Currently spring transactions bind to ThreadLocal.
Are there any plans to support binding to Kotlin coroutines?

For example @transactional over a suspend function maybe should
bind to the coroutine context regardless of the executing thread.

[mp911de]

On a related note: Reactive Transaction Manager integrations for R2DBC and MongoDB are currently in progress. They bind their transactional state to Reactor's subscriber Context.

[sdeleuze]

Depends on Kotlin/kotlinx.coroutines#284 where a PR is WIP.

[sdeleuze]

Moving this one to RC2 since Reactor - Coroutines context is not complete yet, see Kotlin/kotlinx.coroutines#284 (comment) for more details.

[the-fine]

@sdeleuze looks like the work in Kotlin/kotlinx.coroutines#284 was done and released in kotlinx.coroutines 1.3.0-RC2
For @transactional to work with coroutines, it will require just updating to the new coroutines release or there is a work to be done from the spring framework side as well?

[sdeleuze]

I think for annotations it should work with latest Spring Framework master and kotlinx.coroutines 1.3.0-RC2 (not tested yet, if you do please add a comment on this issue). For programmatic usage, I think a helper will be needed, maybe as TransactionalOperator / Flow extensions.

[the-fine]

Looks like it is working only if a reactive(returning publisher) controller method is annotated with @transactional and the rest of the call chain is suspending functions.