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Re: Streaming replication and non-blocking I/O

From: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
To: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Streaming replication and non-blocking I/O
Date: 2010-01-14 09:02:46
Message-ID: 3f0b79eb1001140102n10fdf409id404c6d656aa245b@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Wed, Jan 13, 2010 at 7:27 PM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> the frontend always puts the
> connection to non-blocking mode, while the backend uses blocking mode.

Really? By default (i.e., without the expressly setting by using
PQsetnonblocking()), the connection is set to blocking mode even
in frontend. Am I missing something?

> At least with SSL, I think it's possible for pq_wait() to return false
> positives, if the SSL layer decides to renegotiate the connection
> causing data to flow in the other direction in the underlying TCP
> connection. A false positive would lead cause walsender to block
> indefinitely on the pq_getbyte() call.

Sorry. I could not understand that issue scenario. Could you explain
it in more detail?

Regards,

-- 
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center

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