Re: [HACKERS] Logical Replication WIP
От | Petr Jelinek |
---|---|
Тема | Re: [HACKERS] Logical Replication WIP |
Дата | |
Msg-id | 3b3130df-bcbf-3a34-06b8-022599e47659@2ndquadrant.com обсуждение исходный текст |
Ответ на | Re: [HACKERS] Logical Replication WIP (Fujii Masao <masao.fujii@gmail.com>) |
Список | pgsql-hackers |
On 23/01/17 17:19, Fujii Masao wrote: > On Sat, Jan 21, 2017 at 1:39 AM, Petr Jelinek > <petr.jelinek@2ndquadrant.com> wrote: >> On 20/01/17 17:33, Jaime Casanova wrote: >>> On 20 January 2017 at 11:25, Petr Jelinek <petr.jelinek@2ndquadrant.com> wrote: >>>> On 20/01/17 17:05, Fujii Masao wrote: >>>>> On Fri, Jan 20, 2017 at 11:08 PM, Peter Eisentraut >>>>> <peter.eisentraut@2ndquadrant.com> wrote: >>>>>> On 1/19/17 5:01 PM, Petr Jelinek wrote: >>>>>>> There were some conflicting changes committed today so I rebased the >>>>>>> patch on top of them. >>>>>>> >>>>>>> Other than that nothing much has changed, I removed the separate sync >>>>>>> commit patch, included the rename patch in the patchset and fixed the >>>>>>> bug around pg_subscription catalog reported by Erik Rijkers. >>>>>> >>>>>> Committed. >>>>> >>>>> Sorry I've not followed the discussion about logical replication at all, but >>>>> why does logical replication launcher need to start up by default? >>>>> >>>> >>>> Because running subscriptions is allowed by default. You'd need to set >>>> max_logical_replication_workers to 0 to disable that. >>>> >>> >>> surely wal_level < logical shouldn't start a logical replication >>> launcher, and after an initdb wal_level is only replica >>> >> >> Launcher is needed for subscriptions, subscriptions don't depend on >> wal_level. > > But why did you enable only subscription by default while publication is > disabled by default (i.e., wal_level != logical)? I think that it's better to > enable both by default OR disable both by default. > That depends, the wal_level = logical by default was deemed to not be worth the potential overhead in the thread about wal_level thread. There is no such overhead associated with enabling subscription, one could say that it's less work this way to setup whole thing. But I guess it's up for a debate. > While I was reading the logical rep code, I found that > logicalrep_worker_launch returns *without* releasing LogicalRepWorkerLock > when there is no unused worker slot. This seems a bug. True, fix attached. > > /* Report this after the initial starting message for consistency. */ > if (max_replication_slots == 0) > ereport(ERROR, > (errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED), > errmsg("cannot start logical replication workers when > max_replication_slots = 0"))); > > logicalrep_worker_launch checks max_replication_slots as above. > Why does it need to check that setting value in the *subscriber* side? > Maybe I'm missing something here, but ISTM that the subscription uses > one replication slot in *publisher* side but doesn't use in *subscriber* side. Because replication origins are also limited by the max_replication_slots and they are required for subscription to work (I am not quite sure why it's the case, I guess we wanted to save GUC). > > * The apply worker may spawn additional workers (sync) for initial data > * synchronization of tables. > > The above header comment in logical/worker.c is true? > Hmm not yet, there is separate patch for it in CF, I guess it got through the cracks while rebasing. -- Petr Jelinek http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
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