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</o:shapelayout></xml><![endif]--></head><body lang=DE link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Hello Glyph,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>thank's a lot for this advice! I thought I would have done right, and Twisted-style .. but the select FD trap wasn't on my radar.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><pre><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The <a href="https://github.com/wulczer/txpostgres">https://github.com/wulczer/txpostgres</a> is very interesting. Guess I need to learn about </span>interfaces.IReadWriteDescriptor<o:p></o:p></pre><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>first to grasp it.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Regarding the broader picture: I cannot say I understand what you say completely.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>"</span> maximum file descriptor pollable by select()"<span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Is this *nix in general?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Does that only apply to </span><tt><span style='font-size:10.0pt'>select.select?</span></tt><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Or also: select.poll(), select.epoll(), select.kqueue() ?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>How would implementing an IReadDescriptor circumvent the problem? By not using select(), but poll/epoll/kqeue?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>In any case: we're running FreeBSD, so epoll() is out.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Is there even a kqueue-based Twisted reactor?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Sorry if helping me spawns new questions,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Thanks!<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Tobias<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>for reference (don't know if it applies here):<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>psycopg since v2.2 has<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><a href="http://initd.org/psycopg/docs/advanced.html#asynchronous-support">http://initd.org/psycopg/docs/advanced.html#asynchronous-support</a><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div style='border:none;border-left:solid blue 1.5pt;padding:0cm 0cm 0cm 4.0pt'><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>Von:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> twisted-python-bounces@twistedmatrix.com [mailto:twisted-python-bounces@twistedmatrix.com] <b>Im Auftrag von </b>Glyph<br><b>Gesendet:</b> Donnerstag, 3. November 2011 23:54<br><b>An:</b> Twisted general discussion<br><b>Betreff:</b> Re: [Twisted-Python] adbapi / Postgres : LISTEN/NOTIFY and RealDictCursor<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><div><p class=MsoNormal>On Nov 3, 2011, at 6:18 PM, Tobias Oberstein wrote:<o:p></o:p></p></div><p class=MsoNormal><br><br><o:p></o:p></p><p class=MsoNormal><span class=apple-style-span><span style='font-size:13.5pt;font-family:"Courier New"'> while not self.stopped:</span></span><span style='font-size:13.5pt;font-family:"Courier New"'><br><span class=apple-style-span> if select.select([conn], [], [], self.timeout) == ([], [], []):</span><br><span class=apple-style-span> pass</span><br><br></span><o:p></o:p></p></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal>Please note that on high-volume servers, this is problematic, as 'conn' may be higher than the maximum file descriptor pollable by select(). So if you've tuned everything to be smart, use a high-volume reactor like epoll, and set all your ulimits correctly, you will still get tracebacks out of this code depending on random accidents of ordering.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>This part of the logic might therefore be better implemented as a IReadDescriptor/IWriteDescriptor provider (i.e. a subclass of FileDescriptor), assuming you can ask your postgres binding to give you non-blocking reads and writes. You're certainly not the first person to make this mistake though, <<a href="http://divillo.com/">http://divillo.com/</a>> gives the same advice :).<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Also this would probably make a better patch for txpostgres <<a href="https://launchpad.net/txpostgres">https://launchpad.net/txpostgres</a>> than for Twisted itself, since support depends on specific database bindings.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>-glyph<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div></div></div></body></html>