From: Alan Webb <awebb@linux.vnet.ibm.com>

The change makes two principal implementation changes:

[1] It removes the hard coded set of possible asset server client
implementations, allowing any arbitrary implementation that has been
identified to the PluginLoader as an appropriate extension. The
extension point for asset server client extension
is /OpenSim/AssetServerClient. All of the old configuration rules have
been preserved, and any of the legacy configuration values will still
work as they did before, except the implementation is now loaded as a
plug-in, rather than as a hard-coded instantiation of a specific class.
The re-hashing of IAssetServer as an extension of IPlugin made upgrading
of the implementation classes a necessity.

Caveat: I have not been able to meaningfully test the crypto-grid
clients. I believe they should work correctly, but the refactoring
necessary to handle plug-in based initialization (vs constructor-based
initialisation) admits the possibility of a problem.

[2] The asset cache implementation, previously introduce as a hard-code
class instantiation is now implemented as an IPlugin. Once again the
previous (configurationless) behavior has been preserved. But now it is
possible for those interested in experimenting with cache technologies
to do so simply by introducing a new extension for the asset cache
extension point (/OpenSim/AssetCache).

I've tested all of the configuration settings, after applying the patch
to a newly extracted tree, and they seem to work OK.

2 files changed, 151 insertions, 18 deletions

diff --git a/OpenSim/Region/Application/ConfigurationLoader.cs b/OpenSim/Region/Application/ConfigurationLoader.cs
index 228c0aa..638125c 100644
--- a/OpenSim/Region/Application/ConfigurationLoader.cs
+++ b/OpenSim/Region/Application/ConfigurationLoader.cs
@@ -268,6 +268,7 @@ namespace OpenSim
                 m_configSettings.StorageConnectionString = startupConfig.GetString("storage_connection_string");
                 m_configSettings.EstateConnectionString = startupConfig.GetString("estate_connection_string", m_configSettings.StorageConnectionString);
                 m_configSettings.AssetStorage = startupConfig.GetString("asset_database");
+                m_configSettings.AssetCache = startupConfig.GetString("AssetCache");
                 m_configSettings.ClientstackDll = startupConfig.GetString("clientstack_plugin");
             }
 
diff --git a/OpenSim/Region/Application/OpenSimBase.cs b/OpenSim/Region/Application/OpenSimBase.cs
index 914bd7e..8198138 100644
--- a/OpenSim/Region/Application/OpenSimBase.cs
+++ b/OpenSim/Region/Application/OpenSimBase.cs
@@ -55,6 +55,12 @@ namespace OpenSim
     {
         private static readonly ILog m_log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
 
+        // These are the names of the plugin-points extended by this
+        // class during system startup.
+
+        private const string PLUGIN_ASSET_CACHE         = "/OpenSim/AssetCache";
+        private const string PLUGIN_ASSET_SERVER_CLIENT = "/OpenSim/AssetServerClient";
+
         protected string proxyUrl;
         protected int proxyOffset = 0;                
 
@@ -309,57 +315,183 @@ namespace OpenSim
         }
 
         /// <summary>
-        /// Initialises the assetcache
+        /// Initialises the asset cache. This supports legacy configuration values
+        /// to ensure consistent operation, but values outside of that namespace
+        /// are handled by the more generic resolution mechanism provided by 
+        /// the ResolveAssetServer virtual method. If extended resolution fails, 
+        /// then the normal default action is taken.
+        /// Creation of the AssetCache is handled by ResolveAssetCache. This
+        /// function accepts a reference to the instantiated AssetServer and
+        /// returns an IAssetCache implementation, if possible. This is a virtual
+        /// method.
         /// </summary>
+
         protected virtual void InitialiseAssetCache()
         {
 
+            LegacyAssetServerClientPluginInitialiser linit = null;
+            CryptoAssetServerClientPluginInitialiser cinit = null;
+            AssetServerClientPluginInitialiser        init = null;
+
             IAssetServer assetServer = null;
             string mode = m_configSettings.AssetStorage;
 
-            if (m_configSettings.Standalone   == false &&
-                m_configSettings.AssetStorage == "default")
-                    mode = "grid";
+           if (mode == null | mode == String.Empty)
+                mode = "default";
 
-            switch (mode)
+            // If "default" is specified, then the value is adjusted
+            // according to whether or not the server is running in
+            // standalone mode.
+
+            if (mode.ToLower()  == "default")
             {
+                if (m_configSettings.Standalone == false)
+                        mode = "grid";
+                else
+                        mode = "local";
+            }
+
+            switch (mode.ToLower())
+            {
+
+                // If grid is specified then the grid server is chose regardless 
+                // of whether the server is standalone.
+
                 case "grid" :
-                    assetServer = new GridAssetClient(m_networkServersInfo.AssetURL);
+                    linit = new LegacyAssetServerClientPluginInitialiser(m_configSettings, m_networkServersInfo.AssetURL);
+                    assetServer = loadAssetServer("Grid", linit);
                     break;
+
+
+                // If cryptogrid is specified then the cryptogrid server is chose regardless 
+                // of whether the server is standalone.
+
                 case "cryptogrid" :
-                    assetServer = new CryptoGridAssetClient(m_networkServersInfo.AssetURL,
+                    cinit = new CryptoAssetServerClientPluginInitialiser(m_configSettings, m_networkServersInfo.AssetURL,
                                                         Environment.CurrentDirectory, true);
+                    assetServer = loadAssetServer("Crypto", cinit);
                     break;
+
+                // If cryptogrid_eou is specified then the cryptogrid_eou server is chose regardless 
+                // of whether the server is standalone.
+
                 case "cryptogrid_eou" :
-                    assetServer = new CryptoGridAssetClient(m_networkServersInfo.AssetURL,
+                    cinit = new CryptoAssetServerClientPluginInitialiser(m_configSettings, m_networkServersInfo.AssetURL,
                                                         Environment.CurrentDirectory, false);
+                    assetServer = loadAssetServer("Crypto", cinit);
                     break;
+
+                // If file is specified then the file server is chose regardless 
+                // of whether the server is standalone.
+
                 case "file" :
-                    assetServer = new FileAssetClient(m_networkServersInfo.AssetURL);
+                    linit = new LegacyAssetServerClientPluginInitialiser(m_configSettings, m_networkServersInfo.AssetURL);
+                    assetServer = loadAssetServer("File", linit);
+                    break;
+
+                // If local is specified then we're going to use the local SQL server
+                // implementation. We drop through, because that will be the fallback
+                // for the following default clause too.
+
+                case "local" :
                     break;
+
+                // If the asset_database value is none of the previously mentioned strings, then we
+                // try to load a turnkey plugin that matches this value. If not we drop through to 
+                // a local default.
+
                 default :
-                    if (!ResolveAssetServer(out assetServer))
+                    try
                     {
-                        SQLAssetServer sqlAssetServer = new SQLAssetServer(m_configSettings.StandaloneAssetPlugin, m_configSettings.StandaloneAssetSource);
-                        sqlAssetServer.LoadDefaultAssets(m_configSettings.AssetSetsXMLFile);
-                        assetServer = sqlAssetServer;
+                        init = new AssetServerClientPluginInitialiser(m_configSettings);
+                        assetServer = loadAssetServer(m_configSettings.AssetStorage, init);
+                        break;
                     }
+                    catch {}
+                    m_log.Info("[OPENSIMBASE] Default assetserver will be used");
                     break;
+
+            }
+
+            // Open the local SQL-based database asset server
+
+           if (assetServer == null)
+            {
+                init = new AssetServerClientPluginInitialiser(m_configSettings);
+                SQLAssetServer sqlAssetServer = (SQLAssetServer) loadAssetServer("SQL", init);
+                sqlAssetServer.LoadDefaultAssets(m_configSettings.AssetSetsXMLFile);
+                assetServer = sqlAssetServer;
             }
 
+            // Initialize the asset cache, passing a reference to the selected
+            // asset server interface.
+
             m_assetCache = ResolveAssetCache(assetServer);
 
         }
 
-        private bool ResolveAssetServer(out IAssetServer assetServer)
+        // This method loads the identified asset server, passing an approrpiately
+        // initialized Initialise wrapper. There should to be exactly one match,
+        // if not, then the first match is used.
+
+        private IAssetServer loadAssetServer(string id, PluginInitialiserBase pi)
         {
-            assetServer = null;
-            return false;
+
+            m_log.DebugFormat("[OPENSIMBASE] Attempting to load asset server id={0}", id);
+
+            PluginLoader<IAssetServer> loader = new PluginLoader<IAssetServer>(pi);
+            loader.AddFilter(PLUGIN_ASSET_SERVER_CLIENT, new PluginProviderFilter(id));
+            loader.Load(PLUGIN_ASSET_SERVER_CLIENT);
+           if (loader.Plugins.Count > 0)
+                return (IAssetServer) loader.Plugins[0];
+            else
+                return null;
+
         }
 
-        private IAssetCache ResolveAssetCache(IAssetServer assetServer)
+        /// <summary>
+        /// Attempt to instantiate an IAssetCache implementation, using the
+        /// provided IAssetServer reference.
+        /// An asset cache implementation must provide a constructor that
+        /// accepts two parameters;
+        ///   [1] A ConfigSettings reference.
+        ///   [2] An IAssetServer reference.
+        /// The AssetCache value is obtained from the 
+        /// [StartUp]/AssetCache value in the configuration file.
+        /// </summary>
+
+        protected virtual IAssetCache ResolveAssetCache(IAssetServer assetServer)
         {
-            return new AssetCache(assetServer);
+
+            IAssetCache assetCache = null;
+
+            m_log.DebugFormat("[OPENSIMBASE] Attempting to load asset cache id={0}", m_configSettings.AssetCache);
+
+            if (m_configSettings.AssetCache != null && m_configSettings.AssetCache != String.Empty)
+            {
+                try
+                {
+
+                    PluginInitialiserBase init = new AssetCachePluginInitialiser(m_configSettings, assetServer);
+                    PluginLoader<IAssetCache> loader = new PluginLoader<IAssetCache>(init);
+                    loader.AddFilter(PLUGIN_ASSET_SERVER_CLIENT, new PluginProviderFilter(m_configSettings.AssetCache));
+
+                    loader.Load(PLUGIN_ASSET_CACHE);
+                   if (loader.Plugins.Count > 0)
+                        assetCache = (IAssetCache) loader.Plugins[0];
+     
+                }
+                catch (Exception e)
+                {
+                    m_log.Debug("[OPENSIMBASE] ResolveAssetCache completed");
+                    m_log.Debug(e);
+                }
+            }
+
+            // If everything else fails, we force load the built-in asset cache
+
+            return (IAssetCache) ((assetCache != null) ? assetCache : new AssetCache(assetServer));
+
         }
 
         public void ProcessLogin(bool LoginEnabled)