| From: | "Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com> |
|---|---|
| To: | "Hannu Krosing" <hannu(at)krosing(dot)net> |
| Cc: | "Fujii Masao" <masao(dot)fujii(at)gmail(dot)com>, "Heikki Linnakangas" <heikki(dot)linnakangas(at)enterprisedb(dot)com>, "Simon Riggs" <simon(at)2ndquadrant(dot)com>, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Bruce Momjian" <bruce(at)momjian(dot)us>, "Markus Wanner" <markus(at)bluegap(dot)ch>, "ITAGAKI Takahiro" <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Synchronous Log Shipping Replication |
| Date: | 2008-09-10 06:54:50 |
| Message-ID: | 2e78013d0809092354r467b403dg613a0c033b1f4001@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Sep 10, 2008 at 12:05 PM, Hannu Krosing <hannu(at)krosing(dot)net> wrote:
>
>
>> Because, at the time, current WAL position might be in the middle of
>> WAL file. Even if the master sends only current WAL data, the slave
>> which don't have the corresponding WAL file can not handle it.
>
> I agree, that making initial copy may be outside the scope of
> Synchronous Log Shipping Replication, but slave catching up by
> requesting all missing WAL files and applying these up to a point when
> it can switch to Sync mode should be in. Else we gain very little from
> this patch.
>
I agree. We should leave the initial backup acquisition out of the
scope atleast for the first phase, but provide mechanism to do initial
catch up, as it may get messy to do it completely outside of the core.
The slave will need to able to buffer the *current* WAL until it gets
the missing WAL files and then continue. Also we may not want the
master to be stuck while slave is doing the catchup.
Thanks,
Pavan
--
Pavan Deolasee
EnterpriseDB http://www.enterprisedb.com
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