Comment 9 for bug 132485

Hi there! I'd like to revive this bug.

Since version 2.3, the pyscopg2 driver implements the two-phase commit extension of the DB API specification version 2.0. So I'm keen to pick it up and implement Storm's support for two-phase commit on top of the DB API 2.0 interface.

The idea would be to add a prepare() method to the Store class, as proposed by earlier comments in this bug. Invoking prepare() on a backend that doesn't support the DB API two-phase commit extension would raise NotSupportedError, as recommended in comment #4. Then commit() or rollback() would transparently perform the second phase of the commit, if prepare() was called, as suggested in comment #1.

We might also want to have a begin(transaction_id) method on the Store class, accepting a unique string identifier. This would call the backend's tcp_begin() DB API method under the hood, and can be used by transaction managers.

Integration with ZStorm would be done using the above API, and probably adding something like a set_tpc(flag) method to ZStorm to enable/disable two-phase commit (it would be off by default).

Another option would be to explicitly add two new methods, e.g. tcp_commit() and tcp_rollback(), to clearly mark the difference with commit() and rollback(), though I'm not sure how useful that would be and what the possible use cases are.

Thoughts?