Subject: Re: read-only remote replica
To: Jon Hancock <jhancock@shellshadow.com>, pgsql-admin@postgresql.org
References: 
 <CAOmNu1heCNNMyQd6hFSoMUiBwQpvEg3Yx4n5wqHnEaxvH9JqNA@mail.gmail.com>
From: Ian Barwick <ian@2ndquadrant.com>
Message-ID: <573E6D95.5010007@2ndquadrant.com>
Date: Fri, 20 May 2016 10:51:17 +0900
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On 05/20/2016 08:11 AM, Jon Hancock wrote:
> Hi list,
> I need a read only replica of my postgres server (assume
> current/recent stable release).
> The master is in a reliable data center in California.  The read-only
> replica would be in an office in New Zealand.  Bandwidth can be
> challenging from our office.  It works but bandwidth is highly
> variable.
> 
> The reason for the read-only replica is we have an old reports system
> in our office that connects directly to the db via ODBC.  Simply too
> much work to replace this system for now.  Its not an option to do
> nightly dumps/download/imports as we need closer to real time replica.
> A few minutes delay is ok.
> 
> Any thoughts would be appreciated on how to have a stable/reliable method.

In a previous job I worked with servers running Postgres in different
locations, including New Zealand (have they upgraded the modem used
to connect to the rest of the world yet? ;) ) - if you can live with
occasional lag, streaming replication works pretty well. However
it does of course depend on how much data you'll be receiving - any
idea how many WAL files your master generates in a given period?

One issue to look out for with intercontinental connections is
occasional problems with routing, some router goes down between
you and the data centre and there's nothing you can do but wait
until it's fixed and the route gets updated. To work around that
you could set up WAL archiving using something like Barman [*]
which ships WAL to a different datacentre and set up your replica
to pull files from there if streaming replication is not available.

[*] http://www.pgbarman.org/


Regards

Ian Barwick

-- 
 Ian Barwick                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services


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