Re: Postgres-R: internal messaging

Hi,

That's now changed in today's snapshot of Postgres-R: the postmaster no
longer uses imessages (and thus shared memory) to communicate with the
replication manager. Instead the manager signals the postmaster using a
newish PMSIGNAL for requesting new helper backends. It now only requests
one helper at a time and keeps track of pending requests. The helper
backends now read the name of the database to which they must connect to
from shared memory themselves. That should now adhere to the standard
Postgres rules for shared memory safety.

Additionally, the replication manager is also restarted after a backend
crash, to make sure it never tries to work on corrupted shared memory.
However, that part isn't complete, as the replication manager cannot
really handle that situation just yet. There are other outstanding
issues having to do with that change. Those are documented in the TODO
file in src/backend/replication/.

Regards

Markus Wanner