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

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# --
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# Copyright (C) 2008-2009 10gen Inc.
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#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
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#
# http://www.apache.org/licenses/LICENSE-2.0
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#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
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# ++
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require 'set'
require 'socket'
require 'thread'
module Mongo
# A connection to MongoDB.
class Connection
# We need to make sure that all connection abort when
# a ConnectionError is raised.
Thread.abort_on_exception = true
DEFAULT_PORT = 27017
STANDARD_HEADER_SIZE = 16
RESPONSE_HEADER_SIZE = 20
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attr_reader :logger, :size, :host, :port, :nodes, :sockets, :checked_out
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def slave_ok?
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@slave_ok
end
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# Counter for generating unique request ids.
@@current_request_id = 0
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# Creates a connection to MongoDB. Specify either one or a pair of servers,
# along with a maximum connection pool size and timeout.
#
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# == Connecting
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# If connecting to just one server, you may specify whether connection to slave is permitted.
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#
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# In all cases, the default host is "localhost" and the default port, is 27017.
#
# When specifying a pair, pair_or_host, is a hash with two keys: :left and :right. Each key maps to either
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# * a server name, in which case port is 27017,
# * a port number, in which case the server is "localhost", or
# * an array containing [server_name, port_number]
#
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# === Options
#
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# :slave_ok :: Defaults to +false+. Must be set to +true+ when connecting
# to a single, slave node.
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#
# :logger :: Optional Logger instance to which driver usage information
# will be logged.
#
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# :auto_reconnect :: DEPRECATED. See http://www.mongodb.org/display/DOCS/Replica+Pairs+in+Ruby
#
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# :pool_size :: The maximum number of socket connections that can be opened
# that can be opened to the database.
#
# :timeout :: When all of the connections to the pool are checked out,
# this is the number of seconds to wait for a new connection
# to be released before throwing an exception.
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#
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# === Examples:
#
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# # localhost, 27017
# Connection.new
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#
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# # localhost, 27017
# Connection.new("localhost")
#
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# # localhost, 3000, max 5 connections, with max 5 seconds of wait time.
# Connection.new("localhost", 3000, :pool_size => 5, :timeout => 5)
#
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# # localhost, 3000, where this node may be a slave
# Connection.new("localhost", 3000, :slave_ok => true)
#
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# # A pair of servers. The driver will always talk to master.
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# # On connection errors, Mongo::ConnectionFailure will be raised.
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# # See http://www.mongodb.org/display/DOCS/Replica+Pairs+in+Ruby
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# Connection.new({:left => ["db1.example.com", 27017],
# :right => ["db2.example.com", 27017]})
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#
# A pair of servers, with connection pooling. Not the nil param placeholder for port.
# Connection.new({:left => ["db1.example.com", 27017],
# :right => ["db2.example.com", 27017]}, nil,
# :pool_size => 20, :timeout => 5)
def initialize(pair_or_host=nil, port=nil, options={})
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@nodes = format_pair(pair_or_host, port)
# Host and port of current master.
@host = @port = nil
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# Lock for request ids.
@id_lock = Mutex.new
# Pool size and timeout.
@size = options[:pool_size] || 1
@timeout = options[:timeout] || 5.0
# Mutex for synchronizing pool access
@connection_mutex = Mutex.new
# Condition variable for signal and wait
@queue = ConditionVariable.new
@sockets = []
@checked_out = []
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if options[:auto_reconnect]
warn(":auto_reconnect is deprecated. see http://www.mongodb.org/display/DOCS/Replica+Pairs+in+Ruby")
end
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# Slave ok can be true only if one node is specified
@slave_ok = options[:slave_ok] && @nodes.length == 1
@logger = options[:logger] || nil
@options = options
should_connect = options[:connect].nil? ? true : options[:connect]
connect_to_master if should_connect
end
# Returns a hash with all database names and their respective sizes on
# disk.
def database_info
doc = self['admin'].command(:listDatabases => 1)
returning({}) do |info|
doc['databases'].each { |db| info[db['name']] = db['sizeOnDisk'].to_i }
end
end
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# Returns an array of database names.
def database_names
database_info.keys
end
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# Returns the database named +db_name+. The slave_ok and
# See DB#new for other options you can pass in.
def db(db_name, options={})
DB.new(db_name, self, options.merge(:logger => @logger))
end
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# Returns the database named +db_name+.
def [](db_name)
DB.new(db_name, self, :logger => @logger)
end
# Drops the database +name+.
def drop_database(name)
self[name].command(:dropDatabase => 1)
end
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# Copies the database +from+ on the local server to +to+ on the specified +host+.
# +host+ defaults to 'localhost' if no value is provided.
def copy_database(from, to, host="localhost")
oh = OrderedHash.new
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oh[:copydb] = 1
oh[:fromhost] = host
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oh[:fromdb] = from
oh[:todb] = to
self["admin"].command(oh)
end
# Increments and returns the next available request id.
def get_request_id
request_id = ''
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@id_lock.synchronize do
request_id = @@current_request_id += 1
end
request_id
end
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# Returns the build information for the current connection.
def server_info
db("admin").command({:buildinfo => 1}, {:admin => true, :check_response => true})
end
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# Gets the build version of the current server.
# Returns a ServerVersion object for comparability.
def server_version
ServerVersion.new(server_info["version"])
end
## Connections and pooling ##
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# Sends a message to MongoDB.
#
# Takes a MongoDB opcode, +operation+, a message of class ByteBuffer,
# +message+, and an optional formatted +log_message+.
# Sends the message to the databse, adding the necessary headers.
def send_message(operation, message, log_message=nil)
@logger.debug(" MONGODB #{log_message || message}") if @logger
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packed_message = add_message_headers(operation, message).to_s
socket = checkout
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send_message_on_socket(packed_message, socket)
checkin(socket)
end
# Sends a message to the database, waits for a response, and raises
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# an exception if the operation has failed.
#
# Takes a MongoDB opcode, +operation+, a message of class ByteBuffer,
# +message+, the +db_name+, and an optional formatted +log_message+.
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# Sends the message to the database, adding the necessary headers.
def send_message_with_safe_check(operation, message, db_name, log_message=nil)
message_with_headers = add_message_headers(operation, message)
message_with_check = last_error_message(db_name)
@logger.debug(" MONGODB #{log_message || message}") if @logger
sock = checkout
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packed_message = message_with_headers.append!(message_with_check).to_s
send_message_on_socket(packed_message, sock)
docs, num_received, cursor_id = receive(sock)
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checkin(sock)
if num_received == 1 && error = docs[0]['err']
raise Mongo::OperationFailure, error
end
[docs, num_received, cursor_id]
end
# Sends a message to the database and waits for the response.
#
# Takes a MongoDB opcode, +operation+, a message of class ByteBuffer,
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# +message+, and an optional formatted +log_message+. This method
# also takes an options socket for internal use with #connect_to_master.
def receive_message(operation, message, log_message=nil, socket=nil)
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packed_message = add_message_headers(operation, message).to_s
@logger.debug(" MONGODB #{log_message || message}") if @logger
sock = socket || checkout
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send_message_on_socket(packed_message, sock)
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result = receive(sock)
checkin(sock)
result
end
# Creates a new socket and tries to connect to master.
# If successful, sets @host and @port to master and returns the socket.
def connect_to_master
close
@host = @port = nil
for node_pair in @nodes
host, port = *node_pair
begin
socket = TCPSocket.new(host, port)
socket.setsockopt(Socket::IPPROTO_TCP, Socket::TCP_NODELAY, 1)
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# If we're connected to master, set the @host and @port
result = self['admin'].command({:ismaster => 1}, false, false, socket)
if result['ok'] == 1 && ((is_master = result['ismaster'] == 1) || @slave_ok)
@host, @port = host, port
end
# Note: slave_ok can be true only when connecting to a single node.
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if @nodes.length == 1 && !is_master && !@slave_ok
raise ConfigurationError, "Trying to connect directly to slave; " +
"if this is what you want, specify :slave_ok => true."
end
break if is_master || @slave_ok
rescue SocketError, SystemCallError, IOError => ex
socket.close if socket
false
end
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end
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raise ConnectionFailure, "failed to connect to any given host:port" unless socket
end
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# Are we connected to MongoDB? This is determined by checking whether
# @host and @port have values, since they're set to nil on calls to #close.
def connected?
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@host && @port
end
# Close the connection to the database.
def close
@sockets.each do |sock|
sock.close
end
@host = @port = nil
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@sockets.clear
@checked_out.clear
end
private
# Return a socket to the pool.
def checkin(socket)
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@connection_mutex.synchronize do
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@checked_out.delete(socket)
end
@queue.signal
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true
end
# Adds a new socket to the pool and checks it out.
#
# This method is called exclusively from #obtain_socket;
# therefore, it runs within a mutex, as it must.
def checkout_new_socket
begin
socket = TCPSocket.new(@host, @port)
socket.setsockopt(Socket::IPPROTO_TCP, Socket::TCP_NODELAY, 1)
rescue => ex
raise ConnectionFailure, "Failed to connect socket: #{ex}"
end
@sockets << socket
@checked_out << socket
socket
end
# Checks out the first available socket from the pool.
#
# This method is called exclusively from #obtain_socket;
# therefore, it runs within a mutex, as it must.
def checkout_existing_socket
socket = (@sockets - @checked_out).first
@checked_out << socket
socket
end
# Check out an existing socket or create a new socket if the maximum
# pool size has not been exceeded. Otherwise, wait for the next
# available socket.
def checkout
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connect_to_master if !connected?
start_time = Time.now
loop do
if (Time.now - start_time) > @timeout
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raise ConnectionTimeoutError, "could not obtain connection within " +
"#{@timeout} seconds. The max pool size is currently #{@size}; " +
"consider increasing the pool size or timeout."
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end
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@connection_mutex.synchronize do
socket = if @checked_out.size < @sockets.size
checkout_existing_socket
elsif @sockets.size < @size
checkout_new_socket
end
return socket if socket
# Otherwise, wait
@queue.wait(@connection_mutex)
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end
end
end
def receive(sock)
receive_header(sock)
number_received, cursor_id = receive_response_header(sock)
read_documents(number_received, cursor_id, sock)
end
def receive_header(sock)
header = ByteBuffer.new
header.put_array(receive_message_on_socket(16, sock).unpack("C*"))
unless header.size == STANDARD_HEADER_SIZE
raise "Short read for DB response header: " +
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"expected #{STANDARD_HEADER_SIZE} bytes, saw #{header.size}"
end
header.rewind
size = header.get_int
request_id = header.get_int
response_to = header.get_int
op = header.get_int
end
def receive_response_header(sock)
header_buf = ByteBuffer.new
header_buf.put_array(receive_message_on_socket(RESPONSE_HEADER_SIZE, sock).unpack("C*"))
if header_buf.length != RESPONSE_HEADER_SIZE
raise "Short read for DB response header; " +
"expected #{RESPONSE_HEADER_SIZE} bytes, saw #{header_buf.length}"
end
header_buf.rewind
result_flags = header_buf.get_int
cursor_id = header_buf.get_long
starting_from = header_buf.get_int
number_remaining = header_buf.get_int
[number_remaining, cursor_id]
end
def read_documents(number_received, cursor_id, sock)
docs = []
number_remaining = number_received
while number_remaining > 0 do
buf = ByteBuffer.new
buf.put_array(receive_message_on_socket(4, sock).unpack("C*"))
buf.rewind
size = buf.get_int
buf.put_array(receive_message_on_socket(size - 4, sock).unpack("C*"), 4)
number_remaining -= 1
buf.rewind
docs << BSON.deserialize(buf)
end
[docs, number_received, cursor_id]
end
def last_error_message(db_name)
message = ByteBuffer.new
message.put_int(0)
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BSON_RUBY.serialize_cstr(message, "#{db_name}.$cmd")
message.put_int(0)
message.put_int(-1)
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message.put_array(BSON.serialize({:getlasterror => 1}, false).unpack("C*"))
add_message_headers(Mongo::Constants::OP_QUERY, message)
end
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# Prepares a message for transmission to MongoDB by
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# constructing a valid message header.
def add_message_headers(operation, message)
headers = ByteBuffer.new
# Message size.
headers.put_int(16 + message.size)
# Unique request id.
headers.put_int(get_request_id)
# Response id.
headers.put_int(0)
# Opcode.
headers.put_int(operation)
message.prepend!(headers)
end
# Low-level method for sending a message on a socket.
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# Requires a packed message and an available socket,
def send_message_on_socket(packed_message, socket)
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begin
socket.send(packed_message, 0)
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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)
message = ""
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begin
while message.length < length do
chunk = socket.recv(length - message.length)
raise ConnectionFailure, "connection closed" unless chunk.length > 0
message += chunk
end
rescue => ex
raise ConnectionFailure, "Operation failed with the following exception: #{ex}"
end
message
end
## Private helper methods
# Returns an array of host-port pairs.
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def format_pair(pair_or_host, port)
case pair_or_host
when String
[[pair_or_host, port ? port.to_i : DEFAULT_PORT]]
when Hash
connections = []
connections << pair_val_to_connection(pair_or_host[:left])
connections << pair_val_to_connection(pair_or_host[:right])
connections
when nil
[['localhost', DEFAULT_PORT]]
end
end
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# Turns an array containing a host name string and a
# port number integer into a [host, port] pair array.
def pair_val_to_connection(a)
case a
when nil
['localhost', DEFAULT_PORT]
when String
[a, DEFAULT_PORT]
when Integer
['localhost', a]
when Array
a
end
end
end
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end