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<p class="MsoNormal">Hi Maxim,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Does the allocated memory from connection memory pool for a given connection grow as the number of request grows? If so could you elaborate on how much it grows for a new request? If not, I guess the main reason to limit the request number
is to limit the lifetime of a connection so the connection pool size is under control, right? Is there an parameter to control the lifetime of a http2 connection instead?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks, ChienHsing<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">--------------------------------------------------------------------------------------------------------------------<o:p></o:p></p>
<p class="MsoNormal"><b><span style="font-size:13.5pt;font-family:"Times New Roman",serif;color:black">Maxim Dounin</span></b><span style="font-size:13.5pt;font-family:"Times New Roman",serif;color:black;background:white"> </span><a href="mailto:nginx-devel%40nginx.org?Subject=Re%3A%20HTTP/2%3A%20allow%20unlimited%20number%20of%20requests%20in%20connection&In-Reply-To=%3C20190712142454.GM1877%40mdounin.ru%3E" title="HTTP/2: allow unlimited number of requests in connection"><span style="font-size:13.5pt;font-family:"Times New Roman",serif">mdounin
at mdounin.ru</span></a><span style="font-size:13.5pt;font-family:"Times New Roman",serif;color:black"><br>
<i>Fri Jul 12 14:24:54 UTC 2019</i></span><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<pre><span style="color:black">Hello!<o:p></o:p></span></pre>
<pre><span style="color:black"><o:p> </o:p></span></pre>
<pre><span style="color:black">On Mon, Jul 01, 2019 at 11:24:28AM +0200, Michael Würtinger wrote:<o:p></o:p></span></pre>
<pre><span style="color:black"><o:p> </o:p></span></pre>
<pre><span style="color:black">><i> thanks a lot for your reply. Could you please elaborate a little bit<o:p></o:p></i></span></pre>
<pre><span style="color:black">><i> which memory resources need to be freed periodically? How much memory<o:p></o:p></i></span></pre>
<pre><span style="color:black">><i> can be held by a connection? What's the worst case scenario?<o:p></o:p></i></span></pre>
<pre><span style="color:black">><i> We are currently running it in production with http2_max_requests set<o:p></o:p></i></span></pre>
<pre><span style="color:black">><i> to a value so high that the connection practically lives forever and<o:p></o:p></i></span></pre>
<pre><span style="color:black">><i> so far we cannot spot any problems but maybe we're missing something?<o:p></o:p></i></span></pre>
<pre><span style="color:black"><o:p> </o:p></span></pre>
<pre><span style="color:black">And example of "wost case" can be seen here:<o:p></o:p></span></pre>
<pre><span style="color:black"><o:p> </o:p></span></pre>
<pre><span style="color:black"><a href="http://mailman.nginx.org/pipermail/nginx/2018-July/056525.html">http://mailman.nginx.org/pipermail/nginx/2018-July/056525.html</a><o:p></o:p></span></pre>
<pre><span style="color:black"><o:p> </o:p></span></pre>
<pre><span style="color:black">Memory can be allocated from the connection memory pool. And this <o:p></o:p></span></pre>
<pre><span style="color:black">memory have to be freed at some point - so you have to close <o:p></o:p></span></pre>
<pre><span style="color:black">the connection to do this. And that's why number of requests in a <o:p></o:p></span></pre>
<pre><span style="color:black">particular connection is limited by default.<o:p></o:p></span></pre>
<pre><span style="color:black"><o:p> </o:p></span></pre>
<pre><span style="color:black">Whether or not memory allocations happens in your particular use <o:p></o:p></span></pre>
<pre><span style="color:black">case - doesn't really matter, especially given that things can <o:p></o:p></span></pre>
<pre><span style="color:black">change with seamingly minor configuration and/or client behaviour <o:p></o:p></span></pre>
<pre><span style="color:black">changes.<o:p></o:p></span></pre>
<pre><span style="color:black"><o:p> </o:p></span></pre>
<pre><span style="color:black">In most cases we try to limit allocations from the connection <o:p></o:p></span></pre>
<pre><span style="color:black">memory pool to a minimum, yet it is not always possible/convinient to <o:p></o:p></span></pre>
<pre><span style="color:black">completely avoid allocations from connection memory pool. This <o:p></o:p></span></pre>
<pre><span style="color:black">allows processing of thousands of requests on a single connection <o:p></o:p></span></pre>
<pre><span style="color:black">without observable memory impact. Likely millions will also work <o:p></o:p></span></pre>
<pre><span style="color:black">except may be in some specific use cases, yet I wouldn't recommend <o:p></o:p></span></pre>
<pre><span style="color:black">allowing that many requests, just to be on the safe side.<o:p></o:p></span></pre>
<pre><span style="color:black"><o:p> </o:p></span></pre>
<pre><span style="color:black">-- <o:p></o:p></span></pre>
<pre><span style="color:black">Maxim Dounin<o:p></o:p></span></pre>
<pre><span style="color:black"><a href="http://mdounin.ru/">http://mdounin.ru/</a><o:p></o:p></span></pre>
<p class="MsoNormal"><o:p> </o:p></p>
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