Fixed CSHARP-504. Support read-only GridFS operations when authenticated as a read-only user.

Author: rstam

Driver/GridFS/MongoGridFS.cs

@@ -261,8 +261,6 @@ public void Download(Stream stream, MongoGridFSFileInfo fileInfo)
 
             using (_database.RequestStart(_database.Settings.SlaveOk))
             {
-                EnsureIndexes();
-
                 string md5Client = null;
                 using (var md5Algorithm = _settings.VerifyMD5 ? MD5.Create() : null)
                 {
@@ -325,7 +323,6 @@ public void Download(Stream stream, string remoteFileName)
         /// <param name="version">The version to download.</param>
         public void Download(Stream stream, string remoteFileName, int version)
         {
-            EnsureIndexes();
             Download(stream, Query.EQ("filename", remoteFileName), version);
         }
 
@@ -423,25 +420,10 @@ public void EnsureIndexes()
         /// <param name="maxFiles">Only create new indexes if there are fewer than this number of GridFS files).</param>
         public void EnsureIndexes(int maxFiles)
         {
-            // don't try to create indexes on secondaries
-            var requestConnection = _database.Server.RequestConnection;
-            if (requestConnection != null)
-            {
-                // check whether the actual server instance we are using is a primary
-                var serverInstance = requestConnection.ServerInstance;
-                if (!serverInstance.IsPrimary)
-                {
-                    return;
-                }
-            }
-            else
-            {
-                // check whether we are guaranteed to use a primary
-                if (_database.Settings.SlaveOk)
-                {
-                    return;
-                }
-            }
+            // EnsureIndexes should only be called for update operations
+            // read-only operations shouldn't call EnsureIndexes because:
+            // 1. we might be reading from a secondary
+            // 2. we might be authenticating as a read-only uaser
 
             // avoid round trip to count files if possible
             var indexCache = _database.Server.IndexCache;
@@ -489,7 +471,6 @@ public bool Exists(IMongoQuery query)
         /// <returns>True if the GridFS file exists.</returns>
         public bool Exists(string remoteFileName)
         {
-            EnsureIndexes();
             return Exists(Query.EQ("filename", remoteFileName));
         }
 
@@ -521,7 +502,6 @@ public MongoCursor<MongoGridFSFileInfo> Find(IMongoQuery query)
         /// <returns>The matching GridFS files.</returns>
         public MongoCursor<MongoGridFSFileInfo> Find(string remoteFileName)
         {
-            EnsureIndexes();
             return Find(Query.EQ("filename", remoteFileName));
         }
 
@@ -594,7 +574,6 @@ public MongoGridFSFileInfo FindOne(string remoteFileName)
         /// <returns>The matching GridFS file.</returns>
         public MongoGridFSFileInfo FindOne(string remoteFileName, int version)
         {
-            EnsureIndexes();
             return FindOne(Query.EQ("filename", remoteFileName), version);
         }
 

Driver/GridFS/MongoGridFSFileInfo.cs

@@ -470,7 +470,6 @@ public void Refresh()
             }
             else
             {
-                _gridFS.EnsureIndexes();
                 cursor = _gridFS.Files.Find(Query.EQ("filename", _name)).SetSortOrder(SortBy.Descending("uploadDate"));
             }
             var fileInfo = cursor.SetLimit(1).FirstOrDefault();

Driver/GridFS/MongoGridFSStream.cs

@@ -142,7 +142,6 @@ public MongoGridFSStream(MongoGridFSFileInfo fileInfo, FileMode mode, FileAccess
                     message = string.Format("Invalid FileMode {0}.", mode);
                     throw new ArgumentException(message, "mode");
             }
-            _gridFS.EnsureIndexes();
         }
 
         // public properties
@@ -554,12 +553,16 @@ private void LoadChunkNoData(long chunkIndex)
 
         private void OpenAppend()
         {
+            _gridFS.EnsureIndexes();
+
             _length = _fileInfo.Length;
             _position = _fileInfo.Length;
         }
 
         private void OpenCreate()
         {
+            _gridFS.EnsureIndexes();
+
             _fileIsDirty = true;
             if (_fileInfo.Id == null)
             {
@@ -591,6 +594,8 @@ private void OpenExisting()
 
         private void OpenTruncate()
         {
+            _gridFS.EnsureIndexes();
+
             _fileIsDirty = true;
             // existing chunks will be overwritten as needed and extra chunks will be removed on Close
             _length = 0;