Message-ID: <4D5BEFF9.6020906@enterprisedb.com>
Date: Wed, 16 Feb 2011 17:40:41 +0200
From: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
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To: Simon Riggs <simon@2ndQuadrant.com>
CC: Robert Haas <robertmhaas@gmail.com>, Fujii Masao <masao.fujii@gmail.com>,
	pgsql-hackers@postgresql.org
Subject: Re: Sync Rep for 2011CF1
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	<AANLkTi=boSWVHgjS6EQSOV9K0y_7gokPzS5vj965NT_A@mail.gmail.com>
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On 16.02.2011 17:36, Simon Riggs wrote:
> On Tue, 2011-02-15 at 12:08 -0500, Robert Haas wrote:
>> On Mon, Feb 14, 2011 at 12:25 AM, Fujii Masao<masao.fujii@gmail.com>  wrote:
>>> On Fri, Feb 11, 2011 at 4:06 AM, Heikki Linnakangas
>>> <heikki.linnakangas@enterprisedb.com>  wrote:
>>>> I added a XLogWalRcvSendReply() call into XLogWalRcvFlush() so that it also
>>>> sends a status update every time the WAL is flushed. If the walreceiver is
>>>> busy receiving and flushing, that would happen once per WAL segment, which
>>>> seems sensible.
>>>
>>> This change can make the callback function "WalRcvDie()" call ereport(ERROR)
>>> via XLogWalRcvFlush(). This looks unsafe.
>>
>> Good catch.  Is the cleanest solution to pass a boolean parameter to
>> XLogWalRcvFlush() indicating whether we're in the midst of dying?
>
> Surely if you do this then sync rep will fail to respond correctly if
> WalReceiver dies.
>
> Why is it OK to write to disk, but not OK to reply?

Because the connection might be dead. A broken connection is a likely 
cause of walreceiver death.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com