Add networking module.

lib/mongo/networking.rb

@@ -0,0 +1,337 @@
+module Mongo
+  module Networking
+
+    STANDARD_HEADER_SIZE = 16
+    RESPONSE_HEADER_SIZE = 20
+
+    # Counter for generating unique request ids.
+    @@current_request_id = 0
+
+    # Send a message to MongoDB, adding the necessary headers.
+    #
+    # @param [Integer] operation a MongoDB opcode.
+    # @param [BSON::ByteBuffer] message a message to send to the database.
+    #
+    # @option opts [Symbol] :connection (:writer) The connection to which
+    #   this message should be sent. Valid options are :writer and :reader.
+    #
+    # @return [Integer] number of bytes sent
+    def send_message(operation, message, opts={})
+      if opts.is_a?(String)
+        warn "Connection#send_message no longer takes a string log message. " +
+          "Logging is now handled within the Collection and Cursor classes."
+        opts = {}
+      end
+
+      connection = opts.fetch(:connection, :writer)
+
+      begin
+        add_message_headers(message, operation)
+        packed_message = message.to_s
+
+        if connection == :writer
+          socket = checkout_writer
+        else
+          socket = checkout_reader
+        end
+
+        send_message_on_socket(packed_message, socket)
+      ensure
+        checkin(socket)
+      end
+    end
+
+    # Sends a message to the database, waits for a response, and raises
+    # an exception if the operation has failed.
+    #
+    # @param [Integer] operation a MongoDB opcode.
+    # @param [BSON::ByteBuffer] message a message to send to the database.
+    # @param [String] db_name the name of the database. used on call to get_last_error.
+    # @param [Hash] last_error_params parameters to be sent to getLastError. See DB#error for
+    #   available options.
+    #
+    # @see DB#get_last_error for valid last error params.
+    #
+    # @return [Hash] The document returned by the call to getlasterror.
+    def send_message_with_safe_check(operation, message, db_name, log_message=nil, last_error_params=false)
+      docs = num_received = cursor_id = ''
+      add_message_headers(message, operation)
+
+      last_error_message = BSON::ByteBuffer.new
+      build_last_error_message(last_error_message, db_name, last_error_params)
+      last_error_id = add_message_headers(last_error_message, Mongo::Constants::OP_QUERY)
+
+      packed_message = message.append!(last_error_message).to_s
+      begin
+        sock = checkout_writer
+        send_message_on_socket(packed_message, sock)
+        docs, num_received, cursor_id = receive(sock, last_error_id)
+      ensure
+        checkin(sock)
+      end
+
+      if num_received == 1 && (error = docs[0]['err'] || docs[0]['errmsg'])
+        close if error == "not master"
+        error = "wtimeout" if error == "timeout"
+        raise OperationFailure.new(docs[0]['code'].to_s + ': ' + error, docs[0]['code'], docs[0])
+      end
+
+      docs[0]
+    end
+
+    # Sends a message to the database and waits for the response.
+    #
+    # @param [Integer] operation a MongoDB opcode.
+    # @param [BSON::ByteBuffer] message a message to send to the database.
+    # @param [String] log_message this is currently a no-op and will be removed.
+    # @param [Socket] socket a socket to use in lieu of checking out a new one.
+    # @param [Boolean] command (false) indicate whether this is a command. If this is a command,
+    #   the message will be sent to the primary node.
+    # @param [Boolean] command (false) indicate whether the cursor should be exhausted. Set
+    #   this to true only when the OP_QUERY_EXHAUST flag is set.
+    #
+    # @return [Array]
+    #   An array whose indexes include [0] documents returned, [1] number of document received,
+    #   and [3] a cursor_id.
+    def receive_message(operation, message, log_message=nil, socket=nil, command=false,
+                        read=:primary, exhaust=false)
+      request_id = add_message_headers(message, operation)
+      packed_message = message.to_s
+      begin
+        if socket
+          sock = socket
+          should_checkin = false
+        else
+          if command
+            sock = checkout_writer
+          elsif read == :primary
+            sock = checkout_writer
+          elsif read == :secondary
+            sock = checkout_reader
+          else
+            sock = checkout_tagged(read)
+          end
+          should_checkin = true
+        end
+
+        result = ''
+        @safe_mutexes[sock].synchronize do
+          send_message_on_socket(packed_message, sock)
+          result = receive(sock, request_id, exhaust)
+        end
+      ensure
+        if should_checkin
+          checkin(sock)
+        end
+      end
+      result
+    end
+
+    private
+
+    def receive(sock, cursor_id, exhaust=false)
+      begin
+        if exhaust
+          docs = []
+          num_received = 0
+
+          while(cursor_id != 0) do
+            receive_header(sock, cursor_id, exhaust)
+            number_received, cursor_id = receive_response_header(sock)
+            new_docs, n = read_documents(number_received, sock)
+            docs += new_docs
+            num_received += n
+          end
+
+          return [docs, num_received, cursor_id]
+        else
+          receive_header(sock, cursor_id, exhaust)
+          number_received, cursor_id = receive_response_header(sock)
+          docs, num_received = read_documents(number_received, sock)
+
+          return [docs, num_received, cursor_id]
+        end
+      rescue Mongo::ConnectionFailure => ex
+        close
+        raise ex
+      end
+    end
+
+    def receive_header(sock, expected_response, exhaust=false)
+      header = receive_message_on_socket(16, sock)
+      size, request_id, response_to = header.unpack('VVV')
+      if !exhaust && expected_response != response_to
+        raise Mongo::ConnectionFailure, "Expected response #{expected_response} but got #{response_to}"
+      end
+
+      unless header.size == STANDARD_HEADER_SIZE
+        raise "Short read for DB response header: " +
+          "expected #{STANDARD_HEADER_SIZE} bytes, saw #{header.size}"
+      end
+      nil
+    end
+
+    def receive_response_header(sock)
+      header_buf = receive_message_on_socket(RESPONSE_HEADER_SIZE, sock)
+      if header_buf.length != RESPONSE_HEADER_SIZE
+        raise "Short read for DB response header; " +
+          "expected #{RESPONSE_HEADER_SIZE} bytes, saw #{header_buf.length}"
+      end
+      flags, cursor_id_a, cursor_id_b, starting_from, number_remaining = header_buf.unpack('VVVVV')
+      check_response_flags(flags)
+      cursor_id = (cursor_id_b << 32) + cursor_id_a
+      [number_remaining, cursor_id]
+    end
+
+    def check_response_flags(flags)
+      if flags & Mongo::Constants::REPLY_CURSOR_NOT_FOUND != 0
+        raise Mongo::OperationFailure, "Query response returned CURSOR_NOT_FOUND. " +
+          "Either an invalid cursor was specified, or the cursor may have timed out on the server."
+      elsif flags & Mongo::Constants::REPLY_QUERY_FAILURE != 0
+        # Getting odd failures when a exception is raised here.
+      end
+    end
+
+    def read_documents(number_received, sock)
+      docs = []
+      number_remaining = number_received
+      while number_remaining > 0 do
+        buf = receive_message_on_socket(4, sock)
+        size = buf.unpack('V')[0]
+        buf << receive_message_on_socket(size - 4, sock)
+        number_remaining -= 1
+        docs << BSON::BSON_CODER.deserialize(buf)
+      end
+      [docs, number_received]
+    end
+
+    # Constructs a getlasterror message. This method is used exclusively by
+    # Connection#send_message_with_safe_check.
+    #
+    # Because it modifies message by reference, we don't need to return it.
+    def build_last_error_message(message, db_name, opts)
+      message.put_int(0)
+      BSON::BSON_RUBY.serialize_cstr(message, "#{db_name}.$cmd")
+      message.put_int(0)
+      message.put_int(-1)
+      cmd = BSON::OrderedHash.new
+      cmd[:getlasterror] = 1
+      if opts.is_a?(Hash)
+        opts.assert_valid_keys(:w, :wtimeout, :fsync)
+        cmd.merge!(opts)
+      end
+      message.put_binary(BSON::BSON_CODER.serialize(cmd, false).to_s)
+      nil
+    end
+
+    # Prepares a message for transmission to MongoDB by
+    # constructing a valid message header.
+    #
+    # Note: this method modifies message by reference.
+    #
+    # @return [Integer] the request id used in the header
+    def add_message_headers(message, operation)
+      headers = [
+        # Message size.
+        16 + message.size,
+
+        # Unique request id.
+        request_id = get_request_id,
+
+        # Response id.
+        0,
+
+        # Opcode.
+        operation
+      ].pack('VVVV')
+
+      message.prepend!(headers)
+
+      request_id
+    end
+
+    # Increment and return the next available request id.
+    #
+    # return [Integer]
+    def get_request_id
+      request_id = ''
+      @id_lock.synchronize do
+        request_id = @@current_request_id += 1
+      end
+      request_id
+    end
+
+    # Low-level method for sending a message on a socket.
+    # Requires a packed message and an available socket,
+    #
+    # @return [Integer] number of bytes sent
+    def send_message_on_socket(packed_message, socket)
+      begin
+      total_bytes_sent = socket.send(packed_message, 0)
+      if total_bytes_sent != packed_message.size
+        packed_message.slice!(0, total_bytes_sent)
+        while packed_message.size > 0
+          byte_sent = socket.send(packed_message, 0)
+          total_bytes_sent += byte_sent
+          packed_message.slice!(0, byte_sent)
+        end
+      end
+      total_bytes_sent
+      rescue => ex
+        close
+        raise ConnectionFailure, "Operation failed with the following exception: #{ex}"
+      end
+    end
+
+    # Low-level method for receiving data from socket.
+    # Requires length and an available socket.
+    def receive_message_on_socket(length, socket)
+      begin
+        if @op_timeout
+          message = nil
+          Mongo::TimeoutHandler.timeout(@op_timeout, OperationTimeout) do
+            message = receive_data(length, socket)
+          end
+        else
+          message = receive_data(length, socket)
+        end
+        rescue => ex
+          close
+
+          if ex.class == OperationTimeout
+            raise OperationTimeout, "Timed out waiting on socket read."
+          else
+            raise ConnectionFailure, "Operation failed with the following exception: #{ex}"
+          end
+      end
+      message
+    end
+
+    def receive_data(length, socket)
+      message = new_binary_string
+      socket.read(length, message)
+      raise ConnectionFailure, "connection closed" unless message && message.length > 0
+      if message.length < length
+        chunk = new_binary_string
+        while message.length < length
+          socket.read(length - message.length, chunk)
+          raise ConnectionFailure, "connection closed" unless chunk.length > 0
+          message << chunk
+        end
+      end
+      message
+    end
+
+    if defined?(Encoding)
+      BINARY_ENCODING = Encoding.find("binary")
+
+      def new_binary_string
+        "".force_encoding(BINARY_ENCODING)
+      end
+    else
+      def new_binary_string
+        ""
+      end
+    end
+  end
+end