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Message-ID: <4B741A4F.4000807@2ndquadrant.com>
Date: Thu, 11 Feb 2010 09:55:11 -0500
From: Greg Smith <greg@2ndquadrant.com>
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To: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
CC: Simon Riggs <simon@2ndQuadrant.com>,
	Dimitri Fontaine <dfontaine@hi-media.com>,
	Fujii Masao <masao.fujii@gmail.com>,
	PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: Re: [COMMITTERS] pgsql: Make standby server continuously
	retry 	restoring the next WAL
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Heikki Linnakangas wrote:
> Simon Riggs wrote:
>   
>> Might it not be simpler to add a parameter onto pg_standby?
>> We send %s to tell pg_standby the standby_mode of the server which is
>> calling it so it can decide how to act in each case.
>>     
>
> That would work too, but it doesn't seem any simpler to me. On the contrary.
>   

I don't know that the ideas are mutually exclusive.  Should the server 
internals do a basic check that the files they're about to process seem 
sane before processing them?  Yes.  Should we provide a full-featured 
program that knows how far back it can delete archives rather than 
expecting people to write their own?  Yes.  And a modified pg_standby 
seems the easiest way to do that, since it already knows how to do the 
computations, among other benefits.

I already have a work in progress patch to pg_standby I'm racing to 
finish here that cleans up some of the UI warts in the program, 
including the scary sounding and avoidable warnings Selena submitted a 
patch to improve.  I think I'm going to add this feature to it, too, 
whether or not it's deemed necessary.  I'm really tired of example 
setups provided that say "just write a simple script using cp like 
<trivial example>" and then supporting those non-production quality 
messes in the field.  My scripts for this sort of thing have more error 
checking in them than functional code.  And pg_standby already has a 
healthy sense of paranoia built into it.

-- 
Greg Smith  2ndQuadrant US  Baltimore, MD
PostgreSQL Training, Services and Support
greg@2ndQuadrant.com   www.2ndQuadrant.us


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Heikki Linnakangas wrote:
<blockquote cite="mid:4B7412BE.5030605@enterprisedb.com" type="cite">
  <pre wrap="">Simon Riggs wrote:
  </pre>
  <blockquote type="cite">
    <pre wrap="">Might it not be simpler to add a parameter onto pg_standby?
We send %s to tell pg_standby the standby_mode of the server which is
calling it so it can decide how to act in each case.
    </pre>
  </blockquote>
  <pre wrap=""><!---->
That would work too, but it doesn't seem any simpler to me. On the contrary.
  </pre>
</blockquote>
<br>
I don't know that the ideas are mutually exclusive.&nbsp; Should the server
internals do a basic check that the files they're about to process seem
sane before processing them?&nbsp; Yes.&nbsp; Should we provide a full-featured
program that knows how far back it can delete archives rather than
expecting people to write their own?&nbsp; Yes.&nbsp; And a modified pg_standby
seems the easiest way to do that, since it already knows how to do the
computations, among other benefits.<br>
<br>
I already have a work in progress patch to pg_standby I'm racing to
finish here that cleans up some of the UI warts in the program,
including the scary sounding and avoidable warnings Selena submitted a
patch to improve.&nbsp; I think I'm going to add this feature to it, too,
whether or not it's deemed necessary.&nbsp; I'm really tired of example
setups provided that say "just write a simple script using cp like
&lt;trivial example&gt;" and then supporting those non-production
quality messes in the field.&nbsp; My scripts for this sort of thing have
more error checking in them than functional code.&nbsp; And pg_standby
already has a healthy sense of paranoia built into it.<br>
<br>
<pre class="moz-signature" cols="72">-- 
Greg Smith  2ndQuadrant US  Baltimore, MD
PostgreSQL Training, Services and Support
<a class="moz-txt-link-abbreviated" href="mailto:greg@2ndQuadrant.com">greg@2ndQuadrant.com</a>   <a class="moz-txt-link-abbreviated" href="http://www.2ndQuadrant.us">www.2ndQuadrant.us</a>
</pre>
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