MapGuide Enterprise/OpenSource是通过FDO连接到数据源的。在访问数据源的过程中，MGServer会创建到数据源的FDO连接。为提高性能，连接使用完毕后并不是马上释放，而是放在一个连接池（ConnectionPool）中，下次再使用该FDO连接时，可以先查找连接池中是否有空闲连接，如有空间连接，直接使用连接池中的连接从而省去创建连接的开销；如果连接池中没有可用连接时才会去重新创建，使用完毕后在放置到连接池中。

对应连接池的大小，缺省是200个，但对于不同的FDO连接类型，我们也可以自定义连接池的大小。这些参数就存储在ServerConfig.ini（C:\Program Files\Autodesk\MapGuideEnterprise2010\Server\Bin\serverconfig.ini）文件中。

[FeatureServiceProperties]
# *****************************************************************************
# F E A T U R E  S E R V I C E
#
# Property Name                    Description
# -----------------------------------------------------------------------------
# CacheSize                        Max # of internal data objects to cache
#                                  (schemas, classes, etc...)
#                                       0 < Value <= 5000
# CacheTimeLimit                   Time duration in seconds for how long to
#                                  cache the internal data objects
#                                       0 < Value <= 2147483647
# CacheTimerInterval               Time interval in seconds for when the server
#                                  checks for expired cache entries
#                                       0 < Value <= 2147483647
# DataCacheSize                    Max # of features to fetch
#                                       0 < Value <= 2147483647
# DataConnectionPoolEnabled        FDO connection pooling
#                                       0 = disabled, 1 = enabled
# DataConnectionPoolExcludedProviders  The list of providers to exclude from connection pooling.
#                                       0 <= Length <= 1024
#                                       Value = provider name(s) separated by ","
#                                       Example: OSGeo.SDF,OSGeo.SHP
# DataConnectionPoolSize           Default # of FDO connections to cache per provider
#                                       1 < Value <= 1024
# DataConnectionPoolSizeCustom     Custom # of FDO connections to cache for specified provider
#                                       0 <= Length <= 1024
#                                       Example: OSGeo.SDF:10,OSGeo.SHP:10
# DataConnectionTimeout            Time duration in seconds for when an idle FDO
#                                  connection is dropped
#                                       0 < Value <= 2147483647
# DataConnectionTimerInterval      Time interval in seconds for when the server
#                                  checks for idle FDO connections
#                                       0 < Value <= 2147483647
# JoinQueryBatchSize               Join query batch size
#                                       1 < Value <= 10000
# *****************************************************************************
JoinQueryBatchSize = 1000
DataConnectionTimerInterval = 3600
DataConnectionTimeout = 28800
DataConnectionPoolSizeCustom = OSGeo.Gdal:1
DataConnectionPoolSize = 200
DataConnectionPoolExcludedProviders = OSGeo.SDF,OSGeo.SHP
DataConnectionPoolEnabled = 1
DataCacheSize = 100
CacheTimerInterval = 3600
CacheTimeLimit = 86400
CacheSize = 100

如果我们想设置某种FDO连接的连接池大小，我们就可以通过更改这个配置文件来实现。比如我们需要自定义到ArcSDE的FDO连接池的大小为50个，可以通过更改DataConnectionPoolSizeCustom实现：

DataConnectionPoolSizeCustom = OSGeo.Gdal:1, OSGeo.ArcSDE:50

更改保存完毕，需要重新启动MGServer使改到生效。

另外我们可以通过MapAgent中的测试页面监视FDO连接的使用状况：

通过http://servername/mapagent/index.html 在左边的Feature下的 GetFdoCacheInfo API来查看：

下面是我的MGServer某一时刻的使用状况：

  <?xml version="1.0" encoding="UTF-8" standalone="yes" ?> 
- <FdoCacheInformation>
  <TimeStamp>2009-11-17T17:48:29.702633</TimeStamp> 
- <ConfigurationSettings>
  <DataConnectionPoolEnabled>True</DataConnectionPoolEnabled> 
  <DataConnectionPoolExcludedProviders>OSGeo.SDF,OSGeo.SHP</DataConnectionPoolExcludedProviders> 
  <DataConnectionPoolSize>200</DataConnectionPoolSize> 
  <DataConnectionPoolSizeCustom>OSGeo.Gdal:1</DataConnectionPoolSizeCustom> 
  <DataConnectionTimeout>28800</DataConnectionTimeout> 
  </ConfigurationSettings>
- <Provider>
  <Name>Autodesk.Oracle</Name> 
  <MaximumDataConnectionPoolSize>200</MaximumDataConnectionPoolSize> 
  <CurrentDataConnectionPoolSize>1</CurrentDataConnectionPoolSize> 
  <CurrentDataConnections>0</CurrentDataConnections> 
  <ThreadModel>FdoThreadCapability_PerConnectionThreaded</ThreadModel> 
  <KeepDataConnectionsCached>True</KeepDataConnectionsCached> 
- <CachedFdoConnection>
  <Name>Library://Samples/Sheboygan/Data/Ora.FeatureSource</Name> 
  <ConnectionState>Open</ConnectionState> 
  <InUse>False</InUse> 
  <LongTransaction>LIVE</LongTransaction> 
  <LastUsed>2009-11-17T10:24:02</LastUsed> 
  <Valid>True</Valid> 
  </CachedFdoConnection>
  </Provider>
- <Provider>
  <Name>OSGeo.Gdal</Name> 
  <MaximumDataConnectionPoolSize>1</MaximumDataConnectionPoolSize> 
  <CurrentDataConnectionPoolSize>0</CurrentDataConnectionPoolSize> 
  <CurrentDataConnections>0</CurrentDataConnections> 
  <ThreadModel>Not initialized.</ThreadModel> 
  <KeepDataConnectionsCached>True</KeepDataConnectionsCached> 
  </Provider>
- <Provider>
  <Name>OSGeo.SDF</Name> 
  <MaximumDataConnectionPoolSize>200</MaximumDataConnectionPoolSize> 
  <CurrentDataConnectionPoolSize>0</CurrentDataConnectionPoolSize> 
  <CurrentDataConnections>0</CurrentDataConnections> 
  <ThreadModel>FdoThreadCapability_PerConnectionThreaded</ThreadModel> 
  <KeepDataConnectionsCached>False</KeepDataConnectionsCached> 
  </Provider>
  </FdoCacheInformation>

好了，如果你需要为FDO连接池的大小做定制的话，试试这个吧！ Cheers！

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转载请注明出处及作者 峻祁连 Daniel Du 杜长宇