<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=us-ascii"><meta name=Generator content="Microsoft Word 14 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
@font-face
{font-family:Consolas;
panose-1:2 11 6 9 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
p
{mso-style-priority:99;
mso-margin-top-alt:auto;
margin-right:0in;
mso-margin-bottom-alt:auto;
margin-left:0in;
font-size:12.0pt;
font-family:"Times New Roman","serif";}
p.MsoAcetate, li.MsoAcetate, div.MsoAcetate
{mso-style-priority:99;
mso-style-link:"Balloon Text Char";
margin:0in;
margin-bottom:.0001pt;
font-size:8.0pt;
font-family:"Tahoma","sans-serif";}
span.BalloonTextChar
{mso-style-name:"Balloon Text Char";
mso-style-priority:99;
mso-style-link:"Balloon Text";
font-family:"Tahoma","sans-serif";}
span.EmailStyle20
{mso-style-type:personal;
font-family:"Arial","sans-serif";
color:#8E3432;}
span.EmailStyle21
{mso-style-type:personal;
font-family:"Calibri","sans-serif";
color:windowtext;}
span.EmailStyle22
{mso-style-type:personal;
font-family:"Arial","sans-serif";
color:#1F497D;}
span.EmailStyle23
{mso-style-type:personal;
font-family:"Arial","sans-serif";
color:#993366;}
span.EmailStyle24
{mso-style-type:personal;
font-family:"Calibri","sans-serif";
color:windowtext;}
span.EmailStyle25
{mso-style-type:personal-reply;
font-family:"Calibri","sans-serif";
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>We are having some problems with MapCache running in a multi-server cluster environment. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Occasionally, requests fail for brand new, uncached tiles from a vertical assembly layer (i.e. from other WMS layers as sources). I can confirm this from the server logs:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:Consolas'>Jan 9 18:55:33 server2 httpd[28518]: [error] [client 127.0.0.1] failed to create file /home/caches/NewLayer/gmaps/17/000/036/125/000/082/973.xxx: No such file or directory<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:Consolas'>Jan 9 18:55:33 server2 httpd[28518]: [error] [client 127.0.0.1] failed to create file /home/caches/NewLayer/gmaps/17/000/036/125/000/082/973.xxx: No such file or directory<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Only one tile request is being made, but the failure is logged twice for some reason. It is returned as a blank image with an HTTP 500 error code to the client. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>This error does not appear to be occurring at the tile locking phase, but rather at the point of writing the tile back into the cache directory.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Our setup uses multiple web servers running mapcache under a load balancer. The disk cache directory (and the lock file directory) is shared as an NFS mount. All servers are running the latest version of MapCache from Github as an Apache module on CentOS 5.6. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>This error still occurs when only using one webserver, but it occurs much less frequently. It occurs more frequently when the servers are under a higher load.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Has anyone experienced similar problems?<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='color:black'>John Taranu<o:p></o:p></span></b></p><p class=MsoNormal><span style='color:black'>Senior Web Developer<o:p></o:p></span></p><p class=MsoNormal><span style='color:black'>First Base Solutions Inc<o:p></o:p></span></p><p class=MsoNormal><span style='color:black'>Markham, Ontario<o:p></o:p></span></p><p class=MsoNormal><span style='color:black'>email: </span><span style='color:#244061'><a href="jtaranu@firstbasesolutions.com"><span style='color:#244061'>jtaranu@firstbasesolutions.com</span></a></span><span style='color:black'><o:p></o:p></span></p><p class=MsoNormal><span style='color:black'>web: </span><span style='color:#244061'><a href="http://www.firstbasesolutions.com/"><span style='color:#244061'>firstbasesolutions.com</span></a></span><span style='color:black'><o:p></o:p></span></p><p class=MsoNormal><span style='color:black'><o:p> </o:p></span></p></div></body></html>