mongo-ruby-driver/lib/mongo/db.rb

# --
# Copyright (C) 2008-2009 10gen Inc.
#
# This program is free software: you can redistribute it and/or modify it
# under the terms of the GNU Affero General Public License, version 3, as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License
# for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
# ++

require 'socket'
require 'mutex_m'
require 'mongo/collection'
require 'mongo/message'
require 'mongo/query'
require 'mongo/util/ordered_hash.rb'
require 'mongo/admin'

module XGen
  module Mongo
    module Driver

      # A Mongo database.
      class DB

        SYSTEM_NAMESPACE_COLLECTION = "system.namespaces"
        SYSTEM_INDEX_COLLECTION = "system.indexes"
        SYSTEM_PROFILE_COLLECTION = "system.profile"
        SYSTEM_COMMAND_COLLECTION = "$cmd"

        # Strict mode enforces collection existence checks. When +true+,
        # asking for a collection that does not exist or trying to create a
        # collection that already exists raises an error.
        #
        # Strict mode is off (+false+) by default. Its value can be changed at
        # any time.
        attr_writer :strict

        # Returns the value of the +strict+ flag.
        def strict?; @strict; end

        # The name of the database.
        attr_reader :name

        # Host to which we are currently connected.
        attr_reader :host
        # Port to which we are currently connected.
        attr_reader :port

        # An array of [host, port] pairs.
        attr_reader :nodes

        # The database's socket. For internal (and Cursor) use only.
        attr_reader :socket

        # A primary key factory object (or +nil+). See the README.doc file or
        # DB#new for details.
        attr_reader :pk_factory

        def pk_factory=(pk_factory)
          raise "error: can not change PK factory" if @pk_factory
          @pk_factory = pk_factory
        end

        # db_name :: The database name
        #
        # nodes :: An array of [host, port] pairs.
        #
        # options :: A hash of options.
        #
        # Options:
        #
        # :strict :: If true, collections must exist to be accessed and must
        #            not exist to be created. See #collection and
        #            #create_collection.
        #
        # :pk :: A primary key factory object that must respond to :create_pk,
        #        which should take a hash and return a hash which merges the
        #        original hash with any primary key fields the factory wishes
        #        to inject. (NOTE: if the object already has a primary key,
        #        the factory should not inject a new key; this means that the
        #        object is being used in a repsert but it already exists.) The
        #        idea here is that when ever a record is inserted, the :pk
        #        object's +create_pk+ method will be called and the new hash
        #        returned will be inserted.
        #
        # When a DB object first connects, it tries the first node. If that
        # fails, it keeps trying to connect to the remaining nodes until it
        # sucessfully connects.
        def initialize(db_name, nodes, options={})
          raise "Invalid DB name" if !db_name || (db_name && db_name.length > 0 && db_name.include?("."))
          @name, @nodes = db_name, nodes
          @strict = options[:strict]
          @pk_factory = options[:pk]
          @semaphore = Object.new
          @semaphore.extend Mutex_m
          connect_to_first_available_host
        end

        def connect_to_first_available_host
          close if @socket
          @host = @port = nil
          @nodes.detect { |hp|
            @host, @port = *hp
            begin
              @socket = TCPSocket.new(@host, @port)
              break if ok?(db_command(:ismaster => 1)) # success
            rescue => ex
              close if @socket
            end
            @socket
          }
          raise "error: failed to connect to any given host:port" unless @socket
        end

        # Returns an array of collection names. Each name is of the form
        # "database_name.collection_name".
        def collection_names
          names = collections_info.collect { |doc| doc['name'] || '' }
          names.delete('')
          names
        end

        # Returns a cursor over query result hashes. Each hash contains a
        # 'name' string and optionally an 'options' hash. If +coll_name+ is
        # specified, an array of length 1 is returned.
        def collections_info(coll_name=nil)
          selector = {}
          selector[:name] = full_coll_name(coll_name) if coll_name
          query(Collection.new(self, SYSTEM_NAMESPACE_COLLECTION), Query.new(selector))
        end

        # Create a collection. If +strict+ is false, will return existing or
        # new collection. If +strict+ is true, will raise an error if
        # collection +name+ already exists.
        #
        # Options is an optional hash:
        #
        # :capped :: Boolean. If not specified, capped is +false+.
        #
        # :size :: If +capped+ is +true+, specifies the maximum number of
        #          bytes. If +false+, specifies the initial extent of the
        #          collection.
        #
        # :max :: Max number of records in a capped collection. Optional.
        def create_collection(name, options={})
          # First check existence
          if collection_names.include?(full_coll_name(name))
            if strict?
              raise "Collection #{name} already exists. Currently in strict mode."
            else
              return Collection.new(self, name)
            end
          end

          # Create new collection
          oh = OrderedHash.new
          oh[:create] = name
          doc = db_command(oh.merge(options || {}))
          ok = doc['ok']
          return Collection.new(self, name) if ok.kind_of?(Numeric) && (ok.to_i == 1 || ok.to_i == 0)
          raise "Error creating collection: #{doc.inspect}"
        end

        def admin
          Admin.new(self)
        end

        # Return a collection. If +strict+ is false, will return existing or
        # new collection. If +strict+ is true, will raise an error if
        # collection +name+ does not already exists.
        def collection(name)
          return Collection.new(self, name) if !strict? || collection_names.include?(full_coll_name(name))
          raise "Collection #{name} doesn't exist. Currently in strict mode."
        end

        # Drop collection +name+. Returns +true+ on success or if the
        # collection does not exist, +false+ otherwise.
        def drop_collection(name)
          return true unless collection_names.include?(full_coll_name(name))

          coll = collection(name)
          coll.drop_indexes     # Mongo requires that we drop indexes manually
          ok?(db_command(:drop => name))
        end

        # Returns true if this database is a master (or is not paired with any
        # other database), false if it is a slave.
        def master?
          doc = db_command(:ismaster => 1)
          is_master = doc['ismaster']
          ok?(doc) && is_master.kind_of?(Numeric) && is_master.to_i == 1
        end

        # Returns a string of the form "host:port" that points to the master
        # database. Works even if this is the master database.
        def master
          doc = db_command(:ismaster => 1)
          is_master = doc['ismaster']
          raise "Error retrieving master database" unless ok?(doc) && is_master.kind_of?(Numeric)
          case is_master.to_i
          when 1
            "#@host:#@port"
          else
            doc['remote']
          end
        end

        # Switches our socket to the master database. If we are already the
        # master, no change is made.
        def switch_to_master
          master_str = master()
          unless master_str == "#@host:#@port"
            @semaphore.synchronize {
              master_str =~ /(.+):(\d+)/
              @host, @port = $1, $2
              close()
              @socket = TCPSocket.new(@host, @port)
            }
          end
        end

        # Close the connection to the database.
        def close
          @socket.close if @socket
          @socket = nil
        end

        def connected?
          @socket != nil
        end

        # Send a MsgMessage to the database.
        def send_message(msg)
          send_to_db(MsgMessage.new(msg))
        end
        
        # Returns a Cursor over the query results.
        #
        # Note that the query gets sent lazily; the cursor calls
        # #send_query_message when needed. If the caller never requests an
        # object from the cursor, the query never gets sent.
        def query(collection, query)
          Cursor.new(self, collection, query)
        end

        # Used by a Cursor to lazily send the query to the database.
        def send_query_message(query_message)
          @semaphore.synchronize {
            send_to_db(query_message)
          }
        end

        # Remove the records that match +selector+ from +collection_name+.
        # Normally called by Collection#remove or Collection#clear.
        def remove_from_db(collection_name, selector)
          @semaphore.synchronize {
            send_to_db(RemoveMessage.new(@name, collection_name, selector))
          }
        end

        # Update records in +collection_name+ that match +selector+ by
        # applying +obj+ as an update. Normally called by Collection#replace.
        def replace_in_db(collection_name, selector, obj)
          @semaphore.synchronize {
            send_to_db(UpdateMessage.new(@name, collection_name, selector, obj, false))
          }
        end

        # Alias for #replace_in_db. Normally called by Collection.modify.
        alias_method :modify_in_db, :replace_in_db

        # Update records in +collection_name+ that match +selector+ by
        # applying +obj+ as an update. If no match, inserts (???). Normally
        # called by Collection#repsert.
        def repsert_in_db(collection_name, selector, obj)
          @semaphore.synchronize {
            obj = @pk_factory.create_pk(obj) if @pk_factory
            send_to_db(UpdateMessage.new(@name, collection_name, selector, obj, true))
            obj
          }
        end

        # Return the number of records in +collection_name+ that match
        # +selector+. If +selector+ is +nil+ or an empty hash, returns the
        # count of all records. Normally called by Collection#count.
        def count(collection_name, selector={})
          oh = OrderedHash.new
          oh[:count] = collection_name
          oh[:query] = selector || {}
          doc = db_command(oh)
          return doc['n'].to_i if ok?(doc)
          raise "Error with count command: #{doc.inspect}"
        end

        # Drop index +name+ from +collection_name+. Normally called from
        # Collection#drop_index or Collection#drop_indexes.
        def drop_index(collection_name, name)
          oh = OrderedHash.new
          oh[:deleteIndexes] = collection_name
          oh[:index] = name
          doc = db_command(oh)
          raise "Error with drop_index command: #{doc.inspect}" unless ok?(doc)
        end

        # Return an array of hashes, one for each index on +collection_name+.
        # Normally called by Collection#index_information. Each hash contains:
        #
        # :name :: Index name
        #
        # :keys :: Hash whose keys are the names of the fields that make up
        #          the key and values are integers.
        #
        # :ns :: Namespace; same as +collection_name+.
        def index_information(collection_name)
          sel = {:ns => full_coll_name(collection_name)}
          query(Collection.new(self, SYSTEM_INDEX_COLLECTION), Query.new(sel)).collect { |row|
            h = {:name => row['name']}
            raise "Name of index on return from db was nil. Coll = #{full_coll_name(collection_name)}" unless h[:name]

            h[:keys] = row['key']
            raise "Keys for index on return from db was nil. Coll = #{full_coll_name(collection_name)}" unless h[:keys]

            h[:ns] = row['ns']
            raise "Namespace for index on return from db was nil. Coll = #{full_coll_name(collection_name)}" unless h[:ns]
            h[:ns].sub!(/.*\./, '')
            raise "Error: ns != collection" unless h[:ns] == collection_name

            h
          }
        end

        # Create a new index on +collection_name+ named +index_name+. +fields+
        # should be an array of field names. Normally called by
        # Collection#create_index.
        def create_index(collection_name, index_name, fields)
          sel = {:name => index_name, :ns => full_coll_name(collection_name)}
          field_h = {}
          fields.each { |f| field_h[f] = 1 }
          sel[:key] = field_h
          @semaphore.synchronize {
            send_to_db(InsertMessage.new(@name, SYSTEM_INDEX_COLLECTION, sel))
          }
        end

        # Insert +objects+ into +collection_name+. Normally called by
        # Collection#insert. Returns a new array containing +objects+,
        # possibly modified by @pk_factory.
        def insert_into_db(collection_name, objects)
          @semaphore.synchronize {
            objects.collect { |o|
              o = @pk_factory.create_pk(o) if @pk_factory
              send_to_db(InsertMessage.new(@name, collection_name, o))
              o
            }
          }
        end

        def send_to_db(message)
          @socket.print(message.buf.to_s)
        end

        def full_coll_name(collection_name)
          "#{@name}.#{collection_name}"
        end

        # Return +true+ if +doc+ contains an 'ok' field with the value 1.
        def ok?(doc)
          ok = doc['ok']
          ok.kind_of?(Numeric) && ok.to_i == 1
        end

        # DB commands need to be ordered, so selector must be an OrderedHash
        # (or a Hash with only one element). What DB commands really need is
        # that the "command" key be first.
        #
        # Do not call this. Intended for driver use only.
        def db_command(selector)
          if !selector.kind_of?(OrderedHash)
            if !selector.kind_of?(Hash) || selector.keys.length > 1
              raise "db_command must be given an OrderedHash when there is more than one key"
            end
          end

          q = Query.new(selector)
          q.number_to_return = 1
          query(Collection.new(self, SYSTEM_COMMAND_COLLECTION), q).next_object
        end

      end
    end
  end
end