[mapguide-users] finally

[Kori Maleski]

I think we encountered this as well.  

 

I set up a mirrored server for multi-user data management access and then
push the library package off hours to the production server which is used
for viewing.  This allowed us to utilize the caching for performance on
production.  The crashes stopped completely.

 

Couldn't figure it out for the first while.

 

Kori Maleski

 

From: mapguide-users-bounces at lists.osgeo.org
[mailto:mapguide-users-bounces at lists.osgeo.org] On Behalf Of Haris Kurtagic
Sent: May-19-09 4:59 AM
To: MapGuide Users Mail List
Cc: fdo-users at lists.osgeo.org
Subject: [mapguide-users] finally

 

Finally we found what was causing MapGuide server to crash while reading
data from MapGuide.

It took us lot of energy and time.

 

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.

 

Issue is in function:
MgServerGetFeatures::SerializeToXml(FdoClassDefinition* classDef) 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.

 

Workaround is to set provider to per connection threaded or not cache schema
at all, and both comes with perfomance penalties.

 

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.

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.

 

Haris

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