minor style and doc fixes. warning about logging performance issues.

lib/mongo/collection.rb

@@ -321,7 +321,7 @@ def remove(selector={}, opts={})
       message.put_int(0)
       message.put_binary(BSON::BSON_CODER.serialize(selector, false, true).to_s)
 
-      @connection.instrument( :remove, :database => @db.name, :collection => @name, :selector => selector ) do
+      @connection.instrument(:remove, :database => @db.name, :collection => @name, :selector => selector) do
         if safe
           @connection.send_message_with_safe_check(Mongo::Constants::OP_DELETE, message, @db.name, nil, safe)
         else
@@ -368,7 +368,7 @@ def update(selector, document, opts={})
       message.put_binary(BSON::BSON_CODER.serialize(selector, false, true).to_s)
       message.put_binary(BSON::BSON_CODER.serialize(document, false, true).to_s)
 
-      @connection.instrument( :update, :database => @db.name, :collection => @name, :selector => selector, :document => document ) do
+      @connection.instrument(:update, :database => @db.name, :collection => @name, :selector => selector, :document => document) do
         if safe
           @connection.send_message_with_safe_check(Mongo::Constants::OP_UPDATE, message, @db.name, nil, safe)
         else
@@ -840,7 +840,7 @@ def insert_documents(documents, collection_name=@name, check_keys=true, safe=fal
       end
       raise InvalidOperation, "Exceded maximum insert size of 16,000,000 bytes" if message.size > 16_000_000
 
-      @connection.instrument( :insert, :database => @db.name, :collection => collection_name, :documents => documents ) do
+      @connection.instrument(:insert, :database => @db.name, :collection => collection_name, :documents => documents) do
         if safe
           @connection.send_message_with_safe_check(Mongo::Constants::OP_INSERT, message, @db.name, nil, safe)
         else

lib/mongo/connection.rb

@@ -61,7 +61,8 @@ class Connection
     #   on initialization.
     # @option opts [Boolean] :slave_ok (false) Must be set to +true+ when connecting
     #   to a single, slave node.
-    # @option opts [Logger, #debug] :logger (nil) Logger instance to receive driver operation log.
+    # @option opts [Logger, #debug] :logger (nil) A Logger instance for debugging driver ops. Note that
+    #   logging negatively impacts performance; therefore, it should not be used for high-performance apps.
     # @option opts [Integer] :pool_size (1) The maximum number of socket connections allowed per
     #   connection pool. Note: this setting is relevant only for multi-threaded applications.
     # @option opts [Float] :timeout (5.0) When all of the connections a pool are checked out,
@@ -534,8 +535,10 @@ def checkin_writer(socket)
       end
     end
 
-    # execute the block and log the operation as described by name/payload
-    def instrument( name, payload = {}, &blk )
+    # Execute the block and log the operation described by name
+    # and payload.
+    # TODO: Not sure if this should take a block.
+    def instrument(name, payload = {}, &blk)
       res = yield
       log_operation(name, payload)
       res
@@ -572,7 +575,12 @@ def setup(opts)
       @primary      = nil
       @primary_pool = nil
 
-      @logger   = opts[:logger] || nil
+      @logger = opts[:logger] || nil
+
+      if @logger
+        @logger.debug("MongoDB logging. Please note that logging negatively impacts performance " +
+        "and should be disabled for high-performance production apps.")
+      end
 
       should_connect = opts.fetch(:connect, true)
       connect if should_connect
@@ -596,7 +604,7 @@ def format_pair(host, port)
 
     ## Logging methods
 
-    def log_operation( name, payload )
+    def log_operation(name, payload)
       return unless @logger
       msg = "#{payload[:database]}['#{payload[:collection]}'].#{name}("
       msg += payload.values_at(:selector, :document, :documents, :fields ).compact.map(&:inspect).join(', ') + ")"

lib/mongo/cursor.rb

@@ -378,7 +378,7 @@ def send_initial_query
         false
       else
         message = construct_query_message
-        @connection.instrument( :find, instrument_payload ) do
+        @connection.instrument(:find, instrument_payload) do
           results, @n_received, @cursor_id = @connection.receive_message(
             Mongo::Constants::OP_QUERY, message, nil, @socket, @command)
           @returned += @n_received