Re: Backup throttling

From: Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>
To: Boszormenyi Zoltan <zb(at)cybertec(dot)at>
Cc: Andres Freund <andres(at)2ndquadrant(dot)com>, Antonin Houska <antonin(dot)houska(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Backup throttling
Date: 2013-08-20 06:37:54
Message-ID: 52130EC2.3000500@vmware.com
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On 19.08.2013 21:15, Boszormenyi Zoltan wrote:
> 2013-08-19 19:20 keltezéssel, Andres Freund írta:
>> Based on a quick look it seems like you're throttling on the receiving
>> side. Is that a good idea? Especially over longer latency links, TCP
>> buffering will reduce the effect on the sender side considerably.
>
> Throttling on the sender side requires extending the syntax of
> BASE_BACKUP and maybe START_REPLICATION so both can be
> throttled but throttling is still initiated by the receiver side.

Throttling in the client seems much better to me. TCP is designed to
handle a slow client.

> Maybe throttling the walsender is not a good idea, it can lead
> to DoS via disk space shortage.

If a client can initiate a backup and/or streaming replication, he can
already do much more damage than a DoS via out of disk space. And a
nothing stops even a non-privileged user from causing an out of disk
space situation anyway. IOW that's a non-issue.

- Heikki

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