[Pgpool-general] replication_mode safety

[Jeff Davis]

I have a few questions about the safety of replication_mode in pgpool-
II. There are two cases that I'm thinking about:

(1)

The docs say about replication_strict:
"When set to true, pgpool-II waits for the Master DB for all queries to
be processed before moving on to the next backend. This option
eliminates the risk of deadlocks, but the performance may degrade due to
the lack of a parallelism."

Does this mean that all writes are serialized through pgpool, preventing
any concurrent writes at all, even from different clients?

Or does it just mean that, for a given client, the queries are executed
on the underlying replicants serially?

(2)

If the pgpool server fails suddenly, is it possible that some
transactions may have committed on some replicants and not others? If
so, is there a way to re-synchronize them?

It's possible 2PC would be useful here (?), but it seems like it would
be difficult to change client queries into 2PC transactions.

Regards,
	Jeff Davis