summaryrefslogtreecommitdiff
path: root/lib/rinda/tuplespace.rb
blob: 0490e0ee00cb2698f2226cd70f49c76a4b73dd87 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
#
# = tuplespace: <i>???</i>
#
# <i>Overview of rinda/tuplespace.rb</i> 
#
# <i>Example(s)</i> 
#

require 'monitor'
require 'thread'
require 'drb/drb'
require 'rinda/rinda'

module Rinda
  #
  # A TupleEntry is a Tuple (i.e. a possible entry in some Tuplespace)
  # together with expiry and cancellation data.
  #
  class TupleEntry
    include DRbUndumped

    def initialize(ary, sec=nil)
      @cancel = false
      @ary = make_tuple(ary)
      @renewer = nil
      renew(sec)
    end
    attr_accessor :expires

    def cancel
      @cancel = true
    end

    def alive?
      !canceled? && !expired?
    end

    # Return the object which makes up the tuple itself: the Array
    # or Hash.
    def value; @ary.value; end

    def canceled?; @cancel; end

    # Has this tuple expired? (true/false).
    def expired?
      return true unless @expires
      return false if @expires > Time.now
      return true if @renewer.nil?
      renew(@renewer)
      return true unless @expires
      return @expires < Time.now
    end

    # Reset the expiry data according to the supplied argument. If
    # the argument is:
    #
    # +nil+::    it is set to expire in the far future.
    # +false+::  it has expired.
    # Numeric::  it will expire in that many seconds.
    #
    # Otherwise the argument refers to some kind of renewer object
    # which will reset its expiry time. 
    def renew(sec_or_renewer)
      sec, @renewer = get_renewer(sec_or_renewer)
      @expires = make_expires(sec)
    end

    # Create an expiry time. Called with:
    #
    # +true+:: the expiry time is the start of 1970 (i.e. expired).
    # +nil+::  it is  Tue Jan 19 03:14:07 GMT Standard Time 2038 (i.e. when
    #          UNIX clocks will die)
    #
    # otherwise it is +sec+ seconds into the
    # future.
    def make_expires(sec=nil)
      case sec
      when Numeric
	Time.now + sec
      when true
	Time.at(1)
      when nil
	Time.at(2**31-1)
      end
    end

    # Accessor method for the tuple.
    def [](key)
      @ary[key]
    end

    def fetch(key)
      @ary.fetch(key)
    end

    # The size of the tuple.
    def size
      @ary.size
    end

    # Create a new tuple from the supplied object (array-like).
    def make_tuple(ary)
      Rinda::Tuple.new(ary)
    end

    private
    # Given +true+, +nil+, or +Numeric+, returns that (suitable input to
    # make_expires) and +nil+ (no actual +renewer+), else it return the
    # time data from the supplied +renewer+.
    def get_renewer(it)
      case it
      when Numeric, true, nil
	return it, nil
      else
	begin
	  return it.renew, it
	rescue Exception
	  return it, nil
	end
      end
    end
  end

  #
  # The same as a TupleEntry but with methods to do matching.
  #
  class TemplateEntry < TupleEntry
    def initialize(ary, expires=nil)
      super(ary, expires)
      @template = Rinda::Template.new(ary)
    end

    def match(tuple)
      @template.match(tuple)
    end

    # An alias for #match.
    def ===(tuple)
      match(tuple)
    end

    # Create a new Template from the supplied object.
    def make_tuple(ary)
      Rinda::Template.new(ary)
    end
  end

  #
  # <i>Documentation?</i>
  #
  class WaitTemplateEntry < TemplateEntry
    def initialize(place, ary, expires=nil)
      super(ary, expires)
      @place = place
      @cond = place.new_cond
      @found = nil
    end
    attr_reader :found

    def cancel
      super
      signal
    end

    def wait
      @cond.wait
    end

    def read(tuple)
      @found = tuple
      signal
    end

    def signal
      @place.synchronize do
	@cond.signal
      end
    end
  end

  #
  # <i>Documentation?</i>
  #
  class NotifyTemplateEntry < TemplateEntry
    def initialize(place, event, tuple, expires=nil)
      ary = [event, Rinda::Template.new(tuple)]
      super(ary, expires)
      @queue = Queue.new
      @done = false
    end

    def notify(ev)
      @queue.push(ev)
    end

    def pop
      raise RequestExpiredError if @done
      it = @queue.pop
      @done = true if it[0] == 'close'
      return it
    end

    def each
      while !@done
        it = pop
        yield(it)
      end
    rescue 
    ensure
      cancel
    end
  end

  #
  # TupleBag is an unordered collection of tuples. It is the basis
  # of Tuplespace.
  # 
  class TupleBag
    def initialize
      @hash = {}
    end

    def has_expires?
      @hash.each do |k, v|
        v.each do |tuple|
          return true if tuple.expires
        end
      end
      false
    end

    # Add the object to the TupleBag.
    def push(ary)
      size = ary.size
      @hash[size] ||= []
      @hash[size].push(ary)
    end

    # Remove the object from the TupleBag.
    def delete(ary)
      size = ary.size
      @hash.fetch(size, []).delete(ary)
    end

    # Finds all tuples that match the template and are alive.
    def find_all(template)
      @hash.fetch(template.size, []).find_all do |tuple|
	tuple.alive? && template.match(tuple)
      end
    end

    # Finds a template that matches and is alive.
    def find(template)
      @hash.fetch(template.size, []).find do |tuple|
	tuple.alive? && template.match(tuple)
      end
    end

    # Finds all tuples in the TupleBag which when treated as
    # templates, match the supplied tuple and are alive.
    def find_all_template(tuple)
      @hash.fetch(tuple.size, []).find_all do |template|
	template.alive? && template.match(tuple)
      end
    end

    # Delete tuples which are not alive from the TupleBag. Returns
    # the list of tuples so deleted.
    def delete_unless_alive
      deleted = []
      @hash.keys.each do |size|
	ary = []
	@hash[size].each do |tuple|
	  if tuple.alive?
	    ary.push(tuple)
	  else
	    deleted.push(tuple)
	  end
	end
	@hash[size] = ary
      end
      deleted
    end
  end

  # 
  # The Tuplespace manages access to the tuples it contains,
  # ensuring mutual exclusion requirements are met.
  #
  class TupleSpace
    include DRbUndumped
    include MonitorMixin
    def initialize(period=60)
      super()
      @bag = TupleBag.new
      @read_waiter = TupleBag.new
      @take_waiter = TupleBag.new
      @notify_waiter = TupleBag.new
      @period = period
      @keeper = nil
    end

    # Put a tuple into the tuplespace.
    def write(tuple, sec=nil)
      entry = TupleEntry.new(tuple, sec)
      start_keeper
      synchronize do
	if entry.expired?
	  @read_waiter.find_all_template(entry).each do |template|
	    template.read(tuple)
	  end
	  notify_event('write', entry.value)
	  notify_event('delete', entry.value)
	else
	  @bag.push(entry)
	  @read_waiter.find_all_template(entry).each do |template|
	    template.read(tuple)
	  end
	  @take_waiter.find_all_template(entry).each do |template|
	    template.signal
	  end
	  notify_event('write', entry.value)
	end
      end
      entry
    end

    # Remove an entry from the Tuplespace.
    def take(tuple, sec=nil, &block)
      move(nil, tuple, sec, &block)
    end

    def move(port, tuple, sec=nil)
      template = WaitTemplateEntry.new(self, tuple, sec)
      yield(template) if block_given?
      start_keeper
      synchronize do
	entry = @bag.find(template)
	if entry
	  port.push(entry.value) if port
	  @bag.delete(entry)
	  notify_event('take', entry.value)
	  return entry.value
	end
        raise RequestExpiredError if template.expired?

	begin
	  @take_waiter.push(template)
	  while true
	    raise RequestCanceledError if template.canceled?
	    raise RequestExpiredError if template.expired?
	    entry = @bag.find(template)
	    if entry
	      port.push(entry.value) if port
	      @bag.delete(entry)
	      notify_event('take', entry.value)
	      return entry.value
	    end
	    template.wait
	  end
	ensure
	  @take_waiter.delete(template)
	end
      end
    end

    def read(tuple, sec=nil)
      template = WaitTemplateEntry.new(self, tuple, sec)
      yield(template) if block_given?
      start_keeper
      synchronize do
	entry = @bag.find(template)
	return entry.value if entry
        raise RequestExpiredError if template.expired?

	begin
	  @read_waiter.push(template)
	  template.wait
	  raise RequestCanceledError if template.canceled?
	  raise RequestExpiredError if template.expired?
	  return template.found
	ensure
	  @read_waiter.delete(template)
	end
      end
    end

    def read_all(tuple)
      template = WaitTemplateEntry.new(self, tuple, nil)
      synchronize do
	entry = @bag.find_all(template)
	entry.collect do |e|
	  e.value
	end
      end
    end

    def notify(event, tuple, sec=nil)
      template = NotifyTemplateEntry.new(self, event, tuple, sec)
      synchronize do
	@notify_waiter.push(template)
      end
      template
    end

    private
    def keep_clean
      synchronize do
	@read_waiter.delete_unless_alive.each do |e|
	  e.signal
	end
	@take_waiter.delete_unless_alive.each do |e|
	  e.signal
	end
	@notify_waiter.delete_unless_alive.each do |e|
	  e.notify(['close'])
	end
	@bag.delete_unless_alive.each do |e|
	  notify_event('delete', e.value)
	end
      end
    end

    def notify_event(event, tuple)
      ev = [event, tuple]
      @notify_waiter.find_all_template(ev).each do |template|
	template.notify(ev)
      end
    end

    def start_keeper
      return if @keeper && @keeper.alive?
      @keeper = Thread.new do
        while need_keeper?
          keep_clean
          sleep(@period)
	end
      end
    end

    def need_keeper?
      return true if @bag.has_expires?
      return true if @read_waiter.has_expires?
      return true if @take_waiter.has_expires?
      return true if @notify_waiter.has_expires?
    end
  end
end