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Removing dead connections"></td></tr><tr><td bgcolor="ffffff" width="15">&nbsp;</td><td bgcolor="ffffff" width="12">&nbsp;</td><td valign="top" align="left" bgcolor="ffffff" width="*"><p><br x="7"><table cellspacing="0" cellpadding="0" border="0"><tr><td width="90%"><font size="4" face="Verdana, Arial, Helvetica"><b>The importance of cleaning up</b></font></td><td width="200" align="right"><font size="1" face="Verdana, Arial, Helvetica"><nobr>    page 2 of 2</nobr></font></td></tr></table><br x="7"><br x="7"></p><font size="2" face="Verdana, Arial, Helvetica"><p>This step of removing dead connections is given its own place as
one of our seven elements of server construction because it's so
crucial, and because it's often forgotten by people writing their
first server.</p><p>If programmers forget this step, they find that their server works fine
for a while. Then it begins to get slower and slower, and starts using
more and more memory. When they look at the output of the server
process, they see exceptions whizzing by at an alarming rate.</p><p>What's happened is that the server has kept around all the connections
that have died, is trying to send messages to them, and is finding that it
can't.</p><p>Let's say your server is receiving connections, on average, about once
every five seconds. And let's further assume that the average user
stays on about fifteen minutes.</p><p>This means you will have, on average, about 180 users on at any given
moment. As time passes, many users will connect and disconnect,
keeping the average around 180.</p><p>After 24 hours, 17,280 users will have connected to your server.
At the end of this first day, you'll still have about 180 live
connections, and you'll have about 17,100 dead connections. If you
haven't taken care to remove these dead connections, then you can be
sure that your server is spending most of its time trying, and
failing, to write to these connections. (In fact, it might be
spending most of its time spewing Exceptions to System.out!)</p><p>For this reason, it's <i>crucial</i> that you clean up after these
dead connections.</p><br x="7"></font></td></tr></table><TABLE border="0" cellpadding="0" cellspacing="0" width="100%"><TR><TD align="right" colspan="6"><a border="0" onMouseOver="iOver('topnextsection'); iOver('bottomnextsection'); self.status=nextsectionblurb; return true;" onMouseOut="iOut('topnextsection'); iOut('bottomnextsection'); self.status=''; return true;" href="j-chat-8-1.html"><img alt="Next Section" src="../i/nextsection.gif" border="0" name="bottomnextsection"></a></TD></TR><TR><TD width="100%" colspan="5"></TD><TD width="108" height="1" bgcolor="#000000" align="right"><IMG alt="" height="1" width="108" src="http://www.ibm.com/i/c.gif"></TD></TR><TR><TD background="../i/sw-gold.gif"><a border="0" href="index.html" onMouseOver="iOver('topmain'); iOver('bottommain'); self.status=mainblurb; return true;" onMouseOut="iOut('topmain'); iOut('bottommain'); self.status=''; return true;"><img alt="Main menu" border="0" src="../i/main.gif" name="bottommain"></a></TD><TD background="../i/sw-gold.gif"><a border="0" onMouseOver="iOver('topsection'); iOver('bottomsection'); self.status=sectionblurb; return true;" onMouseOut="iOut('topsection'); iOut('bottomsection'); self.status=''; return true;" href="index7.html"><img alt="Section menu" border="0" src="../i/section.gif" name="bottomsection"></a></TD><TD background="../i/sw-gold.gif"><a border="0" onMouseOver="iOver('topfeedback'); iOver('bottomfeedback'); self.status=feedbackblurb; return true;" onMouseOut="iOut('topfeedback'); iOut('bottomfeedback'); self.status=''; return true;" href="j-chat-11-3.html"><img alt="Give feedback on this tutorial" border="0" src="../i/feedback.gif" name="bottomfeedback"></a></TD><TD width="100%" background="../i/sw-gold.gif"><img src="http://www.ibm.com/i/c.gif"></TD><TD background="../i/sw-gold.gif"><a border="0" onMouseOver="iOver('topprevious'); iOver('bottomprevious'); self.status=previousblurb; return true;" onMouseOut="iOut('topprevious'); iOut('bottomprevious'); self.status=''; return true;" href="j-chat-7-1.html"><img alt="Previous" border="0" src="../i/previous.gif" name="bottomprevious"></a></TD><TD background="../i/sw-gold.gif"><img border="0" src="../i/xnext.gif"></TD></TR><TR><TD width="150" height="1" bgcolor="#000000" colspan="6"><IMG alt="" height="1" width="150" src="http://www.ibm.com/i/c.gif"></TD></TR></TABLE><TABLE cellpadding="0" cellspacing="0" border="0"><TR><TD width="182"><TABLE cellpadding="0" cellspacing="0" border="0" width="182"><TR bgcolor="#000000"><TD align="center" width="60" class="mast"><a style="text-decoration: none; color: #ffffff;" class="nav" href="http://www.ibm.com/privacy/"><font face="Arial, Verdana" size="2">Privacy</font></a></TD><TD width="1" bgcolor="#959595"><img alt="" border="0" height="20" width="1" src="http://www.ibm.com/i/c.gif"></TD><TD align="center" width="60" class="mast"><a style="text-decoration: none; color: #ffffff;" class="nav" href="http://www.ibm.com/legal/"><font face="Arial, Verdana" size="2">Legal</font></a></TD><TD width="1" bgcolor="#959595"><img alt="" border="0" height="20" width="1" src="http://www.ibm.com/i/c.gif"></TD><TD align="center" width="60" class="mast"><a style="text-decoration: none; color: #ffffff;" class="nav" href="http://www.ibm.com/contact/"><font face="Arial, Verdana" size="2">Contact</font></a></TD><TD width="1" bgcolor="#959595"><img alt="" border="0" height="21" width="1" src="http://www.ibm.com/i/c.gif"></TD></TR><TR bgcolor="#ffffff"><TD><img alt="" border="0" height="1" width="1" src="http://www.ibm.com/i/c.gif"></TD></TR></TABLE></TD><TD width="100%"><TABLE cellpadding="0" cellspacing="0" border="0" width="100%"><TR height="21" bgcolor="#000000"><TD><img alt="" border="0" height="21" width="1" src="http://www.ibm.com/i/c.gif"></TD></TR><TR bgcolor="#ffffff"><TD><img alt="" border="0" height="1" width="1" src="http://www.ibm.com/i/c.gif"></TD></TR></TABLE></TD></TR></TABLE></body></html>