Remaining Streaming Replication Open Items

I triaged the list of open items on the Streaming Replication wiki page.
I propose that we drop the ones I've marked as Drop below, and move the
remaining items to the main Open Items page for better visibility. And
of course try to resolve them as quickly as possible.

> * Walsender and dblink are not interruptible on win32. - related thread

I'd actually be happy to just leave it for 9.0, but it seems like
consensus has been reached on how to fix it, and Fujii is working on a
patch, so let's follow that through.

> * Add the GUC parameter to specify the maximum number of log file segments held in pg_xlog directory to send to the standby server. Which is useful to avoid disk full in the primary.

Not only to avoid disk full in primary but also to make it feasible to
use streaming replication without archiving. It's a small change, we
should do it.

> * pg_xlogfile_name(pg_last_xlog_receive/replay_location()) might report the wrong name. Because a backend cannot know the actual timeline which is related to the location.

Drop. It's not clear which timeline those functions should return in
boundary cases, when replaying records from a log file where the
timeline-switch occurs.

> * The documentation needs to be improved.

I've done as much as I can on my own, what we need now is feedback on
what needs to be improved. So I'd like to drop this, but let's add new
more specific items about what needs to be improved, as people speak up.

> * Redefine smart shutdown in standby mode?

Drop. Too big a change at this point.

> * Quotes can't be escaped in recovery.conf

Under discussion. Not specific to streaming replication, and it's a
pre-existing issue, but should be fixed IMHO.

> * Change the "standby mode" name.

Bikeshedding without consensus. I like the "standby mode" the best as
discussed on that thread, better than any of the proposed alternatives.
Drop this item.

> * Fix things so that any such variables inherited from the server environment are intentionally *NOT* used for making SR connections.

Drop. Besides, we have the same problem with dblink, and I don't recall
anyone complaining.

> * If standby_mode is enabled, and neither primary_conninfo nor restore_command are set, the standby would get stuck.

It's not really stuck, it will replay any WAL files you drop into
pg_xlog. I concur with Robert Haas though that it shouldn't print the
message to the log every few seconds. It should print a message the
first time it hits the end of WAL, but subsequent messages should be
suppressed until some progress has been made.

> * Remove the unnecessary section about HS from recovery.conf.sample

Yeah, let's do it.

> * The replication connections consume superuser_reserved_connections slots.

I'd still like to change this slightly, per my suggestion on that
thread, but I don't feel strongly about it. It doesn't seem like a very
big change to me, but Tom felt otherwise.

> * Add missing description about WAL-logging.

Small documentation change. Needs to be done I guess.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com