<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><div>On 10 Oct 2007, at 09:40, Olga Khenkin wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0; "><p class="MsoNormal" style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: Times New Roman; "><font size="2" face="Arial"><span style="font-size:10.0pt; font-family:Arial">When some popular object expires from memcached, all its customers try to retrieve the object from database simultaneously, and the database becomes overloaded.<o:p></o:p></span></font></p><p class="MsoNormal" style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: Times New Roman; "><font size="2" face="Arial"><span style="font-size:10.0pt; font-family:Arial"><o:p> </o:p></span></font></p><p class="MsoNormal" style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: Times New Roman; "><font size="2" face="Arial"><span style="font-size:10.0pt; font-family:Arial">If this object is requested about 100 times in a minute, and if the process of receiving it from DB, processing and storing in cache takes about a minute, then the database receives 100 identical queries.</span></font></p></span></blockquote><br></div><div>The cache evicts stuff on an LRU basis, so anything popular should not be kicked out unless relatively speaking it's really not that popular, in which case you don't have a problem!</div><div><br class="webkit-block-placeholder"></div>If it's really that popular and it's so expensive to create, then you should replace it before it expires.<div><br class="webkit-block-placeholder"></div><div>Marcus<br><div> <span class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: auto; -khtml-text-decorations-in-effect: none; text-indent: 0px; -apple-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><span class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: auto; -khtml-text-decorations-in-effect: none; text-indent: 0px; -apple-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><span class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: auto; -khtml-text-decorations-in-effect: none; text-indent: 0px; -apple-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><div><div style="">-- </div><div style="">Marcus Bointon</div><div style="">Synchromedia Limited: Creators of <a href="http://www.smartmessages.net">http://www.smartmessages.net</a>/</div><div style="">UK resellers of info@hand CRM solutions</div><div style="">marcus@synchromedia.co.uk | <a href="http://www.synchromedia.co.uk">http://www.synchromedia.co.uk</a>/</div></div><br class="Apple-interchange-newline"></span></span></span> </div><br></div></body></html>