On 2017-05-21 06:37, Erik Rijkers wrote:
On 2017-05-20 14:40, Michael Paquier wrote:
On Fri, May 19, 2017 at 3:01 PM, Masahiko Sawada <sawada.m...@gmail.com> wrote:
Also, as Horiguchi-san pointed out earlier, walreceiver seems need the
similar fix.

Actually, now that I look at it, ready_to_display should as well be
protected by the lock of the WAL receiver, so it is incorrectly placed
in walreceiver.h. As you are pointing out, pg_stat_get_wal_receiver()
is lazy as well, and that's new in 10, so we have an open item here
for both of them. And I am the author for both things. No issues
spotted in walreceiverfuncs.c after review.

I am adding an open item so as both issues are fixed in PG10. With the
WAL sender part, I think that this should be a group shot.

So what do you think about the attached?

[walsnd-pid-races-v3.patch]


With this patch on current master my logical replication tests
(pgbench-over-logical-replication) run without errors for the first
time in many days (even weeks).

Unfortunately, just now another logical-replication failure occurred. The same as I have seen all along:

The symptom: after starting logical replication, there are no rows in pg_stat_replication and in the replica-log logical replication complains about max_replication_slots being too low. (from previous experience I know that making max_replication_slots higher does indeed 'help', but only until the next (same) error occurs, with renewed (same) complaint).

Also from previous experience of this failed state I know that it can be 'cleaned up' by
manually emptying these tables:
  delete from pg_subscription_rel;
  delete from pg_subscription;
  delete from pg_replication_origin;
Then it becomes possible to start a new subscription without the above symptoms.

I'll do some more testing and hopefully get some information that's less vague...


Erik Rijkers



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