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Re: pgsql: Efficient transaction-controlled synchronous replication.

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-committers(at)postgresql(dot)org
Subject: Re: pgsql: Efficient transaction-controlled synchronous replication.
Date: 2011-03-10 20:44:33
Message-ID: AANLkTin=49_PyzXvujzRKbY9sxRZQZS9gXc_RePH33k6@mail.gmail.com (view raw or flat)
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Lists: pgsql-committerspgsql-hackers
On Mon, Mar 7, 2011 at 3:27 AM, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
> On Mon, Mar 7, 2011 at 7:51 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>> Efficient transaction-controlled synchronous replication.
>> If a standby is broadcasting reply messages and we have named
>> one or more standbys in synchronous_standby_names then allow
>> users who set synchronous_replication to wait for commit, which
>> then provides strict data integrity guarantees. Design avoids
>> sending and receiving transaction state information so minimises
>> bookkeeping overheads. We synchronize with the highest priority
>> standby that is connected and ready to synchronize. Other standbys
>> can be defined to takeover in case of standby failure.
>>
>> This version has very strict behaviour; more relaxed options
>> may be added at a later date.
>
> Pretty cool! I'd appreciate very much your efforts and contributions.
>
> And,, I found one bug ;) You seem to have wrongly removed the check
> of max_wal_senders in SyncRepWaitForLSN. This can make the
> backend wait for replication even if max_wal_senders = 0. I could produce
> this problematic situation in my machine. The attached patch fixes this problem.

I committed a slightly different fix for this problem.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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