1 | #
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2 | # Note: Rinda::Ring API is unstable.
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3 | #
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4 | require 'drb/drb'
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5 | require 'rinda/rinda'
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6 | require 'thread'
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7 |
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8 | module Rinda
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9 |
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10 | ##
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11 | # The default port Ring discovery will use.
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12 |
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13 | Ring_PORT = 7647
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14 |
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15 | ##
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16 | # A RingServer allows a Rinda::TupleSpace to be located via UDP broadcasts.
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17 | # Service location uses the following steps:
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18 | #
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19 | # 1. A RingServer begins listening on the broadcast UDP address.
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20 | # 2. A RingFinger sends a UDP packet containing the DRb URI where it will
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21 | # listen for a reply.
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22 | # 3. The RingServer recieves the UDP packet and connects back to the
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23 | # provided DRb URI with the DRb service.
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24 |
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25 | class RingServer
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26 |
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27 | include DRbUndumped
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28 |
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29 | ##
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30 | # Advertises +ts+ on the UDP broadcast address at +port+.
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31 |
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32 | def initialize(ts, port=Ring_PORT)
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33 | @ts = ts
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34 | @soc = UDPSocket.open
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35 | @soc.bind('', port)
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36 | @w_service = write_service
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37 | @r_service = reply_service
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38 | end
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39 |
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40 | ##
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41 | # Creates a thread that picks up UDP packets and passes them to do_write
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42 | # for decoding.
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43 |
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44 | def write_service
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45 | Thread.new do
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46 | loop do
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47 | msg = @soc.recv(1024)
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48 | do_write(msg)
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49 | end
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50 | end
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51 | end
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52 |
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53 | ##
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54 | # Extracts the response URI from +msg+ and adds it to TupleSpace where it
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55 | # will be picked up by +reply_service+ for notification.
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56 |
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57 | def do_write(msg)
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58 | Thread.new do
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59 | begin
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60 | tuple, sec = Marshal.load(msg)
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61 | @ts.write(tuple, sec)
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62 | rescue
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63 | end
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64 | end
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65 | end
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66 |
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67 | ##
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68 | # Creates a thread that notifies waiting clients from the TupleSpace.
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69 |
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70 | def reply_service
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71 | Thread.new do
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72 | loop do
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73 | do_reply
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74 | end
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75 | end
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76 | end
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77 |
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78 | ##
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79 | # Pulls lookup tuples out of the TupleSpace and sends their DRb object the
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80 | # address of the local TupleSpace.
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81 |
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82 | def do_reply
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83 | tuple = @ts.take([:lookup_ring, nil])
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84 | Thread.new { tuple[1].call(@ts) rescue nil}
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85 | rescue
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86 | end
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87 |
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88 | end
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89 |
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90 | ##
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91 | # RingFinger is used by RingServer clients to discover the RingServer's
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92 | # TupleSpace. Typically, all a client needs to do is call
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93 | # RingFinger.primary to retrieve the remote TupleSpace, which it can then
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94 | # begin using.
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95 |
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96 | class RingFinger
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97 |
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98 | @@broadcast_list = ['<broadcast>', 'localhost']
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99 |
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100 | @@finger = nil
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101 |
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102 | ##
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103 | # Creates a singleton RingFinger and looks for a RingServer. Returns the
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104 | # created RingFinger.
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105 |
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106 | def self.finger
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107 | unless @@finger
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108 | @@finger = self.new
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109 | @@finger.lookup_ring_any
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110 | end
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111 | @@finger
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112 | end
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113 |
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114 | ##
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115 | # Returns the first advertised TupleSpace.
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116 |
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117 | def self.primary
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118 | finger.primary
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119 | end
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120 |
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121 | ##
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122 | # Contains all discoverd TupleSpaces except for the primary.
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123 |
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124 | def self.to_a
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125 | finger.to_a
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126 | end
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127 |
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128 | ##
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129 | # The list of addresses where RingFinger will send query packets.
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130 |
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131 | attr_accessor :broadcast_list
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132 |
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133 | ##
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134 | # The port that RingFinger will send query packets to.
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135 |
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136 | attr_accessor :port
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137 |
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138 | ##
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139 | # Contain the first advertised TupleSpace after lookup_ring_any is called.
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140 |
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141 | attr_accessor :primary
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142 |
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143 | ##
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144 | # Creates a new RingFinger that will look for RingServers at +port+ on
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145 | # the addresses in +broadcast_list+.
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146 |
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147 | def initialize(broadcast_list=@@broadcast_list, port=Ring_PORT)
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148 | @broadcast_list = broadcast_list || ['localhost']
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149 | @port = port
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150 | @primary = nil
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151 | @rings = []
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152 | end
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153 |
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154 | ##
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155 | # Contains all discovered TupleSpaces except for the primary.
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156 |
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157 | def to_a
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158 | @rings
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159 | end
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160 |
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161 | ##
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162 | # Iterates over all discovered TupleSpaces starting with the primary.
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163 |
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164 | def each
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165 | lookup_ring_any unless @primary
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166 | return unless @primary
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167 | yield(@primary)
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168 | @rings.each { |x| yield(x) }
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169 | end
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170 |
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171 | ##
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172 | # Looks up RingServers waiting +timeout+ seconds. RingServers will be
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173 | # given +block+ as a callback, which will be called with the remote
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174 | # TupleSpace.
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175 |
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176 | def lookup_ring(timeout=5, &block)
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177 | return lookup_ring_any(timeout) unless block_given?
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178 |
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179 | msg = Marshal.dump([[:lookup_ring, DRbObject.new(block)], timeout])
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180 | @broadcast_list.each do |it|
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181 | soc = UDPSocket.open
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182 | begin
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183 | soc.setsockopt(Socket::SOL_SOCKET, Socket::SO_BROADCAST, true)
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184 | soc.send(msg, 0, it, @port)
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185 | rescue
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186 | nil
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187 | ensure
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188 | soc.close
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189 | end
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190 | end
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191 | sleep(timeout)
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192 | end
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193 |
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194 | ##
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195 | # Returns the first found remote TupleSpace. Any further recovered
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196 | # TupleSpaces can be found by calling +to_a+.
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197 |
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198 | def lookup_ring_any(timeout=5)
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199 | queue = Queue.new
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200 |
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201 | th = Thread.new do
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202 | self.lookup_ring(timeout) do |ts|
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203 | queue.push(ts)
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204 | end
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205 | queue.push(nil)
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206 | while it = queue.pop
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207 | @rings.push(it)
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208 | end
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209 | end
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210 |
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211 | @primary = queue.pop
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212 | raise('RingNotFound') if @primary.nil?
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213 | @primary
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214 | end
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215 |
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216 | end
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217 |
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218 | ##
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219 | # RingProvider uses a RingServer advertised TupleSpace as a name service.
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220 | # TupleSpace clients can register themselves with the remote TupleSpace and
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221 | # look up other provided services via the remote TupleSpace.
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222 | #
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223 | # Services are registered with a tuple of the format [:name, klass,
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224 | # DRbObject, description].
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225 |
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226 | class RingProvider
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227 |
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228 | ##
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229 | # Creates a RingProvider that will provide a +klass+ service running on
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230 | # +front+, with a +description+. +renewer+ is optional.
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231 |
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232 | def initialize(klass, front, desc, renewer = nil)
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233 | @tuple = [:name, klass, front, desc]
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234 | @renewer = renewer || Rinda::SimpleRenewer.new
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235 | end
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236 |
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237 | ##
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238 | # Advertises this service on the primary remote TupleSpace.
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239 |
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240 | def provide
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241 | ts = Rinda::RingFinger.primary
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242 | ts.write(@tuple, @renewer)
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243 | end
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244 |
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245 | end
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246 |
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247 | end
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248 |
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249 | if __FILE__ == $0
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250 | DRb.start_service
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251 | case ARGV.shift
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252 | when 's'
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253 | require 'rinda/tuplespace'
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254 | ts = Rinda::TupleSpace.new
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255 | place = Rinda::RingServer.new(ts)
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256 | $stdin.gets
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257 | when 'w'
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258 | finger = Rinda::RingFinger.new(nil)
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259 | finger.lookup_ring do |ts|
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260 | p ts
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261 | ts.write([:hello, :world])
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262 | end
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263 | when 'r'
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264 | finger = Rinda::RingFinger.new(nil)
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265 | finger.lookup_ring do |ts|
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266 | p ts
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267 | p ts.take([nil, nil])
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268 | end
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269 | end
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270 | end
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271 |
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