|From:||Erik Rijkers <er(at)xs4all(dot)nl>|
|To:||Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com>|
|Cc:||Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>|
|Subject:||Re: Logical replication existing data copy|
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On 2017-02-22 14:48, Erik Rijkers wrote:
> On 2017-02-22 13:03, Petr Jelinek wrote:
> It works well now, or at least my particular test case seems now
Cried victory too early, I'm afraid.
The logical replication is now certainly much more stable but there are
still errors, just less often.
The rare 'hang'-error that I mentioned a few emails back I have not yet
encountered; I am beginning to trust that that is indeed solved.
But there is still sometimes incorrect replication. The symptoms are
the ones I mentioned earlier:
- incorrect number of rows in one of (mostly) pgbench_accounts or
the numers are always off by a very small number, say less than 20,
often even only 1 row.
- incorrect content in one of pgbench_accounts or pgbench_history
(detected via md5). Also mostly the two tables named above.
I see sometimes primary key violations on the replica. That should not
be possible if I have understood the intent of logical replication
( ERROR: duplicate key value violates unique constraint
mostly *_tellers, also seen *_branches
Understandably, the errors become more frequent with higher client
counts: a 25x repeat with 1 client yielded only 1 failed run whereas a
25x repeat with 16 clients gave 16 failures.
I attach once more the current incarnation of my test-bash pgbench
Easiest to run it yourself, I guess.
I also attach the output (of pgbench_derail2.sh) of those two 25x
I worry a bit about the correctness of that test program
(pgbench_derail2.sh). I especially wonder if it should look around
better at startup (e.g., at stuff left over from previous iterations).
If you see any incorrect/dumb things there, or a better way to monitor
(aka pre-flight checks), please let me know.
But the current state si certainly a big step forward -- I guess it's
just your bad luck that I had the afternoon off ;)
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