Message-ID: <5330DF08.6020005@archidevsys.co.nz>
Date: Tue, 25 Mar 2014 14:42:32 +1300
From: Gavin Flower <GavinFlower@archidevsys.co.nz>
Organization: ArchiDevSys
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To: Brett Wooldridge <brett.wooldridge@gmail.com>
CC: pgsql-performance@postgresql.org
Subject: Re: Connection pooling - Number of connections
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	<53309465.2000204@archidevsys.co.nz>
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On 25/03/14 13:23, Brett Wooldridge wrote:
> On Tue, Mar 25, 2014 at 5:24 AM, Gavin Flower 
> <GavinFlower@archidevsys.co.nz <mailto:GavinFlower@archidevsys.co.nz>> 
> wrote:
>
>>     Surely no code changes are required, as one can simply set the
>>     min and max pool sizes to be the same?
>     Cheers,
>     Gavin
>
>
> To be sure it can be implemented that way, but its a question of 
> design targets.  For example, if a pool is allowed to grow and shrink, 
> the design might encompass a pool of threads that try to maintain the 
> configured-minimum idle connections to respond to spike demands.  And 
> there is the additional setting in the pool for users to [typically] 
> misconfigure.
>
> However, if the pool is fixed size, and attrition from the pool is 
> only by idle timeout (typically measured in minutes), the design does 
> not need to account for spike demand.  Likely connections that have 
> dropped out can either be restored on-demand rather than something 
> running constantly in the background trying to maintain and idle level.
>
> One of the attributes of HikariCP is a minimalistic set of 
> configuration options with sane defaults, and minimalistic code. 
>  There are many competitor pools, offering dozens of settings ranging 
> form banal to unsafe.  HikariCP initially even offered some of these 
> options, but one-ny-one they're getting the ax.  More and more we're 
> trying to look at what is the true core functionality that user's need 
> -- eliminate what is unnecessary and easily misconfigured.
>
> Thus a debate started over in our group, with some similar views as 
> expressed here (on both sides).  Guillaume Smet was concerned about 
> the impact of idle connections on active ones in PostgreSQL (in a 
> fixed pool scenario) and wanted to ask some of the experts over here.
>
Would it be a valid option to switch in simpler code when min = max and 
both could be set to the same default?  This would allow more efficient 
code to be run for a fixed pool size and allow a sane default, while 
preserving the option to have a range, though obviously not as simple as 
only allowing a fixed pool size in terms of code complexity.


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    <div class="moz-cite-prefix">On 25/03/14 13:23, Brett Wooldridge
      wrote:<br>
    </div>
    <blockquote
cite="mid:CAPg6oRM+0fLGiX-3yGZ3_vU=fKrfs7Ahr=9oO0n0zRDCugu0eA@mail.gmail.com"
      type="cite">
      <div dir="ltr">On Tue, Mar 25, 2014 at 5:24 AM, Gavin Flower <span
          dir="ltr">&lt;<a moz-do-not-send="true"
            href="mailto:GavinFlower@archidevsys.co.nz" target="_blank">GavinFlower@archidevsys.co.nz</a>&gt;</span>
        wrote:<br>
        <div class="gmail_extra">
          <div class="gmail_quote">
            <blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
              <div text="#000000" bgcolor="#FFFFFF">
                <div>
                  <div class="h5">
                    <blockquote type="cite">
                      <div dir="ltr">
                        <div><span style="color:rgb(34,34,34)">Surely no
                            code changes are required, as one can simply
                            set the min and max pool sizes to be the
                            same?</span></div>
                      </div>
                    </blockquote>
                  </div>
                </div>
                Cheers,<br>
                Gavin<br>
              </div>
            </blockquote>
          </div>
          <br>
        </div>
        <div class="gmail_extra">To be sure it can be implemented that
          way, but its a question of design targets. &nbsp;For example, if a
          pool is allowed to grow and shrink, the design might encompass
          a pool of threads that try to maintain the configured-minimum
          idle connections to respond to spike demands. &nbsp;And there is
          the additional setting in the pool for users to [typically]
          misconfigure.</div>
        <div class="gmail_extra"><br>
        </div>
        <div class="gmail_extra">However, if the pool is fixed size, and
          attrition from the pool is only by idle timeout (typically
          measured in minutes), the design does not need to account for
          spike demand. &nbsp;Likely connections that have dropped out can
          either be restored on-demand rather than something running
          constantly in the background trying to maintain and idle
          level.</div>
        <div class="gmail_extra"><br>
        </div>
        <div class="gmail_extra">One of the attributes of HikariCP is a
          minimalistic set of configuration options with sane defaults,
          and minimalistic code. &nbsp;There are many competitor pools,
          offering dozens of settings ranging form banal to unsafe.
          &nbsp;HikariCP initially even offered some of these options, but
          one-ny-one they're getting the ax. &nbsp;More and more we're trying
          to look at what is the true core functionality that user's
          need -- eliminate what is unnecessary and easily
          misconfigured.</div>
        <div class="gmail_extra"><br>
        </div>
        <div class="gmail_extra">Thus a debate started over in our
          group, with some similar views as expressed here (on both
          sides). &nbsp;Guillaume Smet was concerned about the impact of idle
          connections on active ones in PostgreSQL (in a fixed pool
          scenario) and wanted to ask some of the experts over here.</div>
        <div class="gmail_extra"><br>
        </div>
      </div>
    </blockquote>
    Would it be a valid option to switch in simpler code when min = max
    and both could be set to the same default?&nbsp; This would allow more
    efficient code to be run for a fixed pool size and allow a sane
    default, while preserving the option to have a range, though
    obviously not as simple as only allowing a fixed pool size in terms
    of code complexity.<br>
    <br>
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