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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";
color:black'>Finally we found what was causing MapGuide server to crash while reading
data from MapGuide.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";
color:black'>It took us lot of energy and time.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";
color:black'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";
color:black'>Problem will appear in multiuser environment with concurent access
when you are using provider which is per command threaded or sharing (caching)
FDO schema accross multiple connections.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";
color:black'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New";
color:black'>Issue is in function: MgServerGetFeatures</span><span
style='font-size:10.0pt;font-family:"Courier New"'>::<span style='color:black'>SerializeToXml</span>(<span
style='color:black'>FdoClassDefinition</span>* <span style='color:black'>classDef</span>)
which will in order to serialize class to xml remove that class from schema, put
it to temporary schema serialize and return class to original schema. While doing
this if another thread goes to execute, problem starts.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>Workaround
is to set provider to per connection threaded or not cache schema at all, and both
comes with perfomance penalties.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>I
think that few things are important in this case beside the obvious issue. One
of them is missing constant pointers in FDO API. Schema returned from provider
shouldn't be allowed to be changed by fdo clients. That is something were problems
appeared already.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>Also,
I think that serialization using XML is not right way to go. XML we could use
to serialize data to end-user not for internal MG processes.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Courier New"'>Haris</span><o:p></o:p></p>
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