Re: [COMMITTERS] pgsql: Replication lag tracking for walsenders

From: Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [COMMITTERS] pgsql: Replication lag tracking for walsenders
Date: 2017-04-22 13:54:11
Message-ID: CAEepm=1-QRkb3Y+hO+tQVyKqH9dp0GVVWkMmsMDy1izpVZ4XLw@mail.gmail.com
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On Sat, Apr 22, 2017 at 9:13 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> On 22 April 2017 at 06:45, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> wrote:
>
>> Thanks. I'm away from my computer right now but will investigate this
>> and send a fix later today.
>
> Thanks. I'll review later today.

The assertion fails reliably for me, because standby2's reported write
LSN jumps backwards after the timeline changes: for example I see
3020000 then 3028470 then 3020000 followed by a normal progression.
Surprisingly, 004_timeline_switch.pl reports success anyway. I'm not
sure why the test fails sometimes on tern, but you can see that even
when it passed on tern the assertion had failed.

Here is a fix for the assertion failure.

--
Thomas Munro
http://www.enterprisedb.com

Attachment Content-Type Size
fix-lag-tracker-for-backwards-lsn-jump.patch application/octet-stream 725 bytes

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