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

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# encoding: UTF-8
# --
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# Copyright (C) 2008-2011 10gen Inc.
#
# 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
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# 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.
# ++
module Mongo
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# Instantiates and manages connections to a MongoDB replica set.
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class ReplSetConnection < Connection
attr_reader :nodes, :secondaries, :arbiters, :read_pool, :secondary_pools
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# Create a connection to a MongoDB replica set.
#
# Once connected to a replica set, you can find out which nodes are primary, secondary, and
# arbiters with the corresponding accessors: Connection#primary, Connection#secondaries, and
# Connection#arbiters. This is useful if your application needs to connect manually to nodes other
# than the primary.
#
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# @param [Array] args A list of host-port pairs to be used as seed nodes followed by a
# hash containing any options. See the examples below for exactly how to use the constructor.
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#
# @option options [String] :rs_name (nil) The name of the replica set to connect to. You
# can use this option to verify that you're connecting to the right replica set.
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# @option options [Boolean, Hash] :safe (false) Set the default safe-mode options
# propogated to DB objects instantiated off of this Connection. This
# default can be overridden upon instantiation of any DB by explicity setting a :safe value
# on initialization.
# @option options [Boolean] :read_secondary(false) If true, a random secondary node will be chosen,
# and all reads will be directed to that node.
# @option options [Logger, #debug] :logger (nil) Logger instance to receive driver operation log.
# @option options [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 options [Float] :timeout (5.0) When all of the connections a pool are checked out,
# this is the number of seconds to wait for a new connection to be released before throwing an exception.
# Note: this setting is relevant only for multi-threaded applications.
#
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# @example Connect to a replica set and provide two seed nodes. Note that the number of seed nodes does
# not have to be equal to the number of replica set members. The purpose of seed nodes is to permit
# the driver to find at least one replica set member even if a member is down.
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# ReplSetConnection.new(['localhost', 30000], ['localhost', 30001])
#
# @example Connect to a replica set providing two seed nodes and ensuring a connection to the replica set named 'prod':
# ReplSetConnection.new(['localhost', 30000], ['localhost', 30001], :rs_name => 'prod')
#
# @example Connect to a replica set providing two seed nodes and allowing reads from a secondary node:
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# ReplSetConnection.new(['localhost', 30000], ['localhost', 30001], :read_secondary => true)
#
# @see http://api.mongodb.org/ruby/current/file.REPLICA_SETS.html Replica sets in Ruby
#
# @raise [ReplicaSetConnectionError] This is raised if a replica set name is specified and the
# driver fails to connect to a replica set with that name.
def initialize(*args)
if args.last.is_a?(Hash)
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opts = args.pop
else
opts = {}
end
unless args.length > 0
raise MongoArgumentError, "A ReplSetConnection requires at least one node."
end
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# Get seed nodes
@nodes = args
# Replica set name
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@replica_set = opts[:rs_name]
# Cache the various node types when connecting to a replica set.
@secondaries = []
@arbiters = []
# Connection pools for each secondary node
@secondary_pools = []
@read_pool = nil
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# Are we allowing reads from secondaries?
@read_secondary = opts.fetch(:read_secondary, false)
setup(opts)
end
# Create a new socket and attempt to connect to master.
# If successful, sets host and port to master and returns the socket.
#
# If connecting to a replica set, this method will replace the
# initially-provided seed list with any nodes known to the set.
#
# @raise [ConnectionFailure] if unable to connect to any host or port.
def connect
reset_connection
@nodes_to_try = @nodes.clone
while connecting?
node = @nodes_to_try.shift
config = check_is_master(node)
if is_primary?(config)
set_primary(node)
else
set_auxillary(node, config)
end
end
pick_secondary_for_read if @read_secondary
if connected?
BSON::BSON_CODER.update_max_bson_size(self)
else
if @secondary_pools.empty?
close # close any existing pools and sockets
raise ConnectionFailure, "Failed to connect any given host:port"
else
close # close any existing pools and sockets
raise ConnectionFailure, "Failed to connect to primary node."
end
end
end
alias :reconnect :connect
def connecting?
@nodes_to_try.length > 0
end
# The replica set primary's host name.
#
# @return [String]
def host
super
end
# The replica set primary's port.
#
# @return [Integer]
def port
super
end
# Determine whether we're reading from a primary node. If false,
# this connection connects to a secondary node and @read_secondaries is true.
#
# @return [Boolean]
def read_primary?
!@read_pool
end
alias :primary? :read_primary?
# Close the connection to the database.
def close
super
@read_pool = nil
@secondary_pools.each do |pool|
pool.close
end
end
# If a ConnectionFailure is raised, this method will be called
# to close the connection and reset connection values.
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# TODO: what's the point of this method?
def reset_connection
super
@secondaries = []
@secondary_pools = []
@arbiters = []
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@nodes_tried = []
@nodes_to_try = []
end
# Is it okay to connect to a slave?
#
# @return [Boolean]
def slave_ok?
@read_secondary || @slave_ok
end
def authenticate_pools
super
@secondary_pools.each do |pool|
pool.authenticate_existing
end
end
def logout_pools(db)
super
@secondary_pools.each do |pool|
pool.logout_existing(db)
end
end
private
def check_is_master(node)
begin
host, port = *node
socket = TCPSocket.new(host, port)
socket.setsockopt(Socket::IPPROTO_TCP, Socket::TCP_NODELAY, 1)
config = self['admin'].command({:ismaster => 1}, :socket => socket)
check_set_name(config, socket)
rescue OperationFailure, SocketError, SystemCallError, IOError => ex
# It's necessary to rescue here. The #connect method will keep trying
# until it has no more nodes to try and raise a ConnectionFailure if
# it can't connect to a primary.
ensure
socket.close if socket
@nodes_tried << node
if config
nodes = []
nodes += config['hosts'] if config['hosts']
nodes += config['arbiters'] if config['arbiters']
nodes += config['passives'] if config['passives']
update_node_list(nodes)
if config['msg'] && @logger
@logger.warn("MONGODB #{config['msg']}")
end
end
end
config
end
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# Primary, when connecting to a replica can, can only be a true primary node.
# (And not a slave, which is possible when connecting with the standard
# Connection class.
def is_primary?(config)
config && (config['ismaster'] == 1 || config['ismaster'] == true)
end
# Pick a node randomly from the set of possible secondaries.
def pick_secondary_for_read
if (size = @secondary_pools.size) > 0
@read_pool = @secondary_pools[rand(size)]
end
end
# Make sure that we're connected to the expected replica set.
def check_set_name(config, socket)
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if @replica_set
config = self['admin'].command({:replSetGetStatus => 1},
:socket => socket, :check_response => false)
if !Mongo::Support.ok?(config)
raise ReplicaSetConnectionError, config['errmsg']
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elsif config['set'] != @replica_set
raise ReplicaSetConnectionError,
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"Attempting to connect to replica set '#{config['set']}' but expected '#{@replica_set}'"
end
end
end
# Determines what kind of node we have and caches its host
# and port so that users can easily connect manually.
def set_auxillary(node, config)
if config
if config['secondary']
host, port = *node
@secondaries << node unless @secondaries.include?(node)
@secondary_pools << Pool.new(self, host, port, :size => @pool_size, :timeout => @timeout)
elsif config['arbiterOnly']
@arbiters << node unless @arbiters.include?(node)
end
end
end
# Update the list of known nodes. Only applies to replica sets,
# where the response to the ismaster command will return a list
# of known hosts.
#
# @param hosts [Array] a list of hosts, specified as string-encoded
# host-port values. Example: ["myserver-1.org:27017", "myserver-1.org:27017"]
#
# @return [Array] the updated list of nodes
def update_node_list(hosts)
new_nodes = hosts.map do |host|
if !host.respond_to?(:split)
warn "Could not parse host #{host.inspect}."
next
end
host, port = host.split(':')
[host, port ? port.to_i : Connection::DEFAULT_PORT]
end
# Replace the list of seed nodes with the canonical list.
@nodes = new_nodes.clone
@nodes_to_try = new_nodes - @nodes_tried
end
# Checkout a socket for reading (i.e., a secondary node).
def checkout_reader
connect unless connected?
if @read_pool
@read_pool.checkout
else
checkout_writer
end
end
# Checkout a socket for writing (i.e., a primary node).
def checkout_writer
connect unless connected?
@primary_pool.checkout
end
# Checkin a socket used for reading.
def checkin_reader(socket)
if @read_pool
@read_pool.checkin(socket)
else
checkin_writer(socket)
end
end
# Checkin a socket used for writing.
def checkin_writer(socket)
if @primary_pool
@primary_pool.checkin(socket)
end
end
end
end