Class: MemCache

Inherits:
Object
  • Object
show all
Defined in:
lib/memcache.rb

Overview

A Ruby client library for memcached.

Defined Under Namespace

Classes: MemCacheError, Server

Constant Summary collapse

VERSION =

The version of MemCache you are using.

'1.7.1.2'
DEFAULT_OPTIONS =

Default options for the cache object.

{
  :namespace          => nil,
  :readonly           => false,
  :multithread        => true,
  :failover           => true,
  :timeout            => 0.5,
  :logger             => nil,
  :raw                => false,
  :persistent_hashing => true,
  :no_reply    	=> false,
}
DEFAULT_PORT =

Default memcached port.

11211
DEFAULT_WEIGHT =

Default memcached server weight.

1
ONE_MB =

Add key to the cache with value value that expires in expiry seconds. If raw is true, value will not be Marshalled.

Warning: Readers should not call this method in the event of a cache miss; see MemCache#add.

1024 * 1024

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(*args) ⇒ MemCache

Accepts a list of servers and a list of opts. servers may be omitted. See servers= for acceptable server list arguments.

Valid options for opts are:

[:namespace]   Prepends this value to all keys added or retrieved.
[:readonly]    Raises an exception on cache writes when true.
[:multithread] Wraps cache access in a Mutex for thread safety. Defaults to true.
[:failover]    Should the client try to failover to another server if the
               first server is down?  Defaults to true.
[:timeout]     Time to use as the socket read timeout.  Defaults to 0.5 sec,
               set to nil to disable timeouts (this is a major performance penalty in Ruby 1.8,
               "gem install SystemTimer' to remove most of the penalty).
[:logger]      Logger to use for info/debug output, defaults to nil
[:raw]         If true, the value(s) will be returned unaltered.
[:persistent_hashing]
               If true do persisting hashing otherwise do modulo hashing, defaults to true.
[:no_reply]    Don't bother looking for a reply for write operations (i.e. they
               become 'fire and forget'), memcached 1.2.5 and later only, speeds up
               set/add/delete/incr/decr significantly.

Other options are ignored.



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
# File 'lib/memcache.rb', line 125

def initialize(*args)
  servers = []
  opts = {}

  case args.length
  when 0 then # NOP
  when 1 then
    arg = args.shift
    case arg
    when Hash   then opts = arg
    when Array  then servers = arg
    when String then servers = [arg]
    else raise ArgumentError, 'first argument must be Array, Hash or String'
    end
  when 2 then
    servers, opts = args
  else
    raise ArgumentError, "wrong number of arguments (#{args.length} for 2)"
  end

  opts = DEFAULT_OPTIONS.merge opts
  @namespace          = opts[:namespace]
  @readonly           = opts[:readonly]
  @multithread        = opts[:multithread]
  @timeout            = opts[:timeout]
  @failover           = opts[:failover]
  @logger             = opts[:logger]
  @raw                = opts[:raw]
  @persistent_hashing = opts[:persistent_hashing]
  @no_reply    = opts[:no_reply]
  @mutex              = Mutex.new if @multithread

  logger.info { "memcache-client #{VERSION} #{Array(servers).inspect}" } if logger

  self.servers = servers
end

Instance Attribute Details

#failoverObject (readonly)

Should the client try to failover to another server if the first server is down? Defaults to true.



88
89
90
# File 'lib/memcache.rb', line 88

def failover
  @failover
end

#loggerObject (readonly)

Log debug/info/warn/error to the given Logger, defaults to nil.



93
94
95
# File 'lib/memcache.rb', line 93

def logger
  @logger
end

#multithreadObject (readonly)

The multithread setting for this instance



71
72
73
# File 'lib/memcache.rb', line 71

def multithread
  @multithread
end

#namespaceObject (readonly)

The namespace for this instance



66
67
68
# File 'lib/memcache.rb', line 66

def namespace
  @namespace
end

#no_replyObject (readonly)

Don’t send or look for a reply from the memcached server for write operations. Please note this feature only works in memcached 1.2.5 and later. Earlier versions will reply with “ERROR”.



99
100
101
# File 'lib/memcache.rb', line 99

def no_reply
  @no_reply
end

#serversObject

The servers this client talks to. Play at your own peril.



76
77
78
# File 'lib/memcache.rb', line 76

def servers
  @servers
end

#timeoutObject (readonly)

Socket timeout limit with this client, defaults to 0.5 sec. Set to nil to disable timeouts.



82
83
84
# File 'lib/memcache.rb', line 82

def timeout
  @timeout
end

Instance Method Details

#[]=(key, value) ⇒ Object

Shortcut to save a value in the cache. This method does not set an expiration on the entry. Use set to specify an explicit expiry.



640
641
642
# File 'lib/memcache.rb', line 640

def []=(key, value)
  set key, value
end

#active?Boolean

Returns whether there is at least one active server for the object.

Returns:

  • (Boolean)


173
174
175
# File 'lib/memcache.rb', line 173

def active?
  not @servers.empty?
end

#add(key, value, expiry = 0, raw = nil) ⇒ Object

Add key to the cache with value value that expires in expiry seconds, but only if key does not already exist in the cache. If raw is true, value will not be Marshalled.

Readers should call this method in the event of a cache miss, not MemCache#set.

Raises:



424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
# File 'lib/memcache.rb', line 424

def add(key, value, expiry = 0, raw = nil)
  raise MemCacheError, "Update of readonly cache" if @readonly
  with_server(key) do |server, cache_key|
    value = Marshal.dump value unless (raw == nil && @raw) || raw
    logger.debug { "add #{key} to #{server}: #{value ? value.to_s.size : 'nil'}" } if logger
    command = "add #{cache_key} 0 #{expiry} #{value.to_s.size}#{noreply}\r\n#{value}\r\n"

    with_socket_management(server) do |socket|
      socket.write command
      break nil if @no_reply
      result = socket.gets
      raise_on_error_response! result
      result
    end
  end
end

#append(key, value) ⇒ Object

Append - ‘add this data to an existing key after existing data’ Please note the value is always passed to memcached as raw since it doesn’t make a lot of sense to concatenate marshalled data together.

Raises:



466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
# File 'lib/memcache.rb', line 466

def append(key, value)
  raise MemCacheError, "Update of readonly cache" if @readonly
  with_server(key) do |server, cache_key|
    logger.debug { "append #{key} to #{server}: #{value ? value.to_s.size : 'nil'}" } if logger
    command = "append #{cache_key} 0 0 #{value.to_s.size}#{noreply}\r\n#{value}\r\n"

    with_socket_management(server) do |socket|
      socket.write command
      break nil if @no_reply
      result = socket.gets
      raise_on_error_response! result
      result
    end
  end
end

#cache_decr(server, cache_key, amount) ⇒ Object

Performs a raw decr for cache_key from server. Returns nil if not found.



697
698
699
700
701
702
703
704
705
706
# File 'lib/memcache.rb', line 697

def cache_decr(server, cache_key, amount)
  with_socket_management(server) do |socket|
    socket.write "decr #{cache_key} #{amount}#{noreply}\r\n"
    break nil if @no_reply
    text = socket.gets
    raise_on_error_response! text
    return nil if text == "NOT_FOUND\r\n"
    return text.to_i
  end
end

#cache_get(server, cache_key) ⇒ Object

Fetches the raw data for cache_key from server. Returns nil on cache miss.



712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
# File 'lib/memcache.rb', line 712

def cache_get(server, cache_key)
  with_socket_management(server) do |socket|
    socket.write "get #{cache_key}\r\n"
    keyline = socket.gets # "VALUE <key> <flags> <bytes>\r\n"

    if keyline.nil? then
      server.close
      raise MemCacheError, "lost connection to #{server.host}:#{server.port}"
    end

    raise_on_error_response! keyline
    return nil if keyline == "END\r\n"

    unless keyline =~ /(\d+)\r/ then
      server.close
      raise MemCacheError, "unexpected response #{keyline.inspect}"
    end
    value = socket.read $1.to_i
    socket.read 2 # "\r\n"
    socket.gets   # "END\r\n"
    return value
  end
end

#cache_get_multi(server, cache_keys) ⇒ Object

Fetches cache_keys from server using a multi-get.



772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
# File 'lib/memcache.rb', line 772

def cache_get_multi(server, cache_keys)
  with_socket_management(server) do |socket|
    values = {}
    socket.write "get #{cache_keys}\r\n"

    while keyline = socket.gets do
      return values if keyline == "END\r\n"
      raise_on_error_response! keyline

      unless keyline =~ /\AVALUE (.+) (.+) (.+)/ then
        server.close
        raise MemCacheError, "unexpected response #{keyline.inspect}"
      end

      key, data_length = $1, $3
      values[$1] = socket.read data_length.to_i
      socket.read(2) # "\r\n"
    end

    server.close
    raise MemCacheError, "lost connection to #{server.host}:#{server.port}" # TODO: retry here too
  end
end

#cache_incr(server, cache_key, amount) ⇒ Object

Performs a raw incr for cache_key from server. Returns nil if not found.



800
801
802
803
804
805
806
807
808
809
# File 'lib/memcache.rb', line 800

def cache_incr(server, cache_key, amount)
  with_socket_management(server) do |socket|
    socket.write "incr #{cache_key} #{amount}#{noreply}\r\n"
    break nil if @no_reply
    text = socket.gets
    raise_on_error_response! text
    return nil if text == "NOT_FOUND\r\n"
    return text.to_i
  end
end

#cas(key, expiry = 0, raw = nil) ⇒ Object

“cas” is a check and set operation which means “store this data but only if no one else has updated since I last fetched it.” This can be used as a form of optimistic locking.

Works in block form like so:

cache.cas('some-key') do |value|
  value + 1
end

Returns: nil if the value was not found on the memcached server. STORED if the value was updated successfully EXISTS if the value was updated by someone else since last fetch

Raises:



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
# File 'lib/memcache.rb', line 387

def cas(key, expiry=0, raw=nil)
  raise MemCacheError, "Update of readonly cache" if @readonly
  raise MemCacheError, "A block is required" unless block_given?

  (value, token) = gets(key, raw)
  return nil unless value
  value = yield value

  with_server(key) do |server, cache_key|
    value = Marshal.dump value unless (raw == nil && @raw) || raw
    logger.debug { "cas #{key} to #{server.inspect}: #{value.to_s.size}" } if logger
    command = "cas #{cache_key} 0 #{expiry} #{value.to_s.size} #{token}#{noreply}\r\n#{value}\r\n"

    with_socket_management(server) do |socket|
      socket.write command
      break nil if @no_reply
      result = socket.gets
      raise_on_error_response! result

      if result.nil?
        server.close
        raise MemCacheError, "lost connection to #{server.host}:#{server.port}"
      end

      result
    end
  end
end

#create_continuum_for(servers) ⇒ Object



903
904
905
906
907
908
909
910
911
912
913
914
915
916
# File 'lib/memcache.rb', line 903

def create_continuum_for(servers)
  total_weight = servers.inject(0) { |memo, srv| memo + srv.weight }
  continuum = []

  servers.each do |server|
    entry_count_for(server, servers.size, total_weight).times do |idx|
      hash = Digest::SHA1.hexdigest("#{server.host}:#{server.port}:#{idx}")
      value = Integer("0x#{hash[0..7]}")
      continuum << Continuum::Entry.new(value, server)
    end
  end

  continuum.sort { |a, b| a.value <=> b.value }
end

#decr(key, amount = 1) ⇒ Object

Decrements the value for key by amount and returns the new value. key must already exist. If key is not an integer, it is assumed to be

  1. key can not be decremented below 0.



225
226
227
228
229
230
231
232
# File 'lib/memcache.rb', line 225

def decr(key, amount = 1)
  raise MemCacheError, "Update of readonly cache" if @readonly
  with_server(key) do |server, cache_key|
    cache_decr server, cache_key, amount
  end
rescue TypeError => err
  handle_error nil, err
end

#delete(key, expiry = 0) ⇒ Object

Removes key from the cache in expiry seconds.

Raises:



505
506
507
508
509
510
511
512
513
514
515
516
517
# File 'lib/memcache.rb', line 505

def delete(key, expiry = 0)
  raise MemCacheError, "Update of readonly cache" if @readonly
  with_server(key) do |server, cache_key|
    with_socket_management(server) do |socket|
      logger.debug { "delete #{cache_key} on #{server}" } if logger
      socket.write "delete #{cache_key} #{expiry}#{noreply}\r\n"
      break nil if @no_reply
      result = socket.gets
      raise_on_error_response! result
      result
    end
  end
end

#entry_count_for(server, total_servers, total_weight) ⇒ Object



918
919
920
# File 'lib/memcache.rb', line 918

def entry_count_for(server, total_servers, total_weight)
  ((total_servers * Continuum::POINTS_PER_SERVER * server.weight) / Float(total_weight)).floor
end

#fetch(key, expiry = 0, raw = false) ⇒ Object

Performs a get with the given key. If the value does not exist and a block was given, the block will be called and the result saved via add.

If you do not provide a block, using this method is the same as using get.



258
259
260
261
262
263
264
265
266
267
# File 'lib/memcache.rb', line 258

def fetch(key, expiry = 0, raw = false)
  value = get(key, raw)

  if value.nil? && block_given?
    value = yield
    add(key, value, expiry, raw)
  end

  value
end

#flush_all(delay = 0) ⇒ Object

Flush the cache from all memcache servers. A non-zero value for delay will ensure that the flush is propogated slowly through your memcached server farm. The Nth server will be flushed N*delay seconds from now, asynchronously so this method returns quickly. This prevents a huge database spike due to a total flush all at once.

Raises:



528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
# File 'lib/memcache.rb', line 528

def flush_all(delay=0)
  raise MemCacheError, 'No active servers' unless active?
  raise MemCacheError, "Update of readonly cache" if @readonly

  begin
    delay_time = 0
    @servers.each do |server|
      with_socket_management(server) do |socket|
        logger.debug { "flush_all #{delay_time} on #{server}" } if logger
        socket.write "flush_all #{delay_time}#{noreply}\r\n"
        break nil if @no_reply
        result = socket.gets
        raise_on_error_response! result
        result
      end
      delay_time += delay
    end
  rescue IndexError => err
    handle_error nil, err
  end
end

#get(key, raw = nil) ⇒ Object Also known as: []

Retrieves key from memcache. If raw is false, the value will be unmarshalled.



238
239
240
241
242
243
244
245
246
247
248
# File 'lib/memcache.rb', line 238

def get(key, raw = nil)
  with_server(key) do |server, cache_key|
    value = cache_get server, cache_key
    logger.debug { "get #{key} from #{server.inspect}: #{value ? value.to_s.size : 'nil'}" } if logger
    return nil if value.nil?
    value = Marshal.load value unless (raw == nil && @raw) || raw
    return value
  end
rescue TypeError => err
  handle_error nil, err
end

#get_multi(*keys) ⇒ Object

Retrieves multiple values from memcached in parallel, if possible.

The memcached protocol supports the ability to retrieve multiple keys in a single request. Pass in an array of keys to this method and it will:

  1. map the key to the appropriate memcached server

  2. send a single request to each server that has one or more key values

Returns a hash of values.

cache["a"] = 1
cache["b"] = 2
cache.get_multi "a", "b" # => { "a" => 1, "b" => 2 }

Note that get_multi assumes the values are marshalled.



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
# File 'lib/memcache.rb', line 287

def get_multi(*keys)
  raise MemCacheError, 'No active servers' unless active?

  keys.flatten!
  key_count = keys.length
  cache_keys = {}
  server_keys = Hash.new { |h,k| h[k] = [] }

  # map keys to servers
  keys.each do |key|
    server, cache_key = request_setup key
    cache_keys[cache_key] = key
    server_keys[server] << cache_key
  end

  results = {}

  server_keys.each do |server, keys_for_server|
    keys_for_server_str = keys_for_server.join ' '
    begin
      values = cache_get_multi server, keys_for_server_str
      values.each do |key, value|
        results[cache_keys[key]] = if @raw then value else Marshal.load value end
      end
    rescue IndexError => e
      # Ignore this server and try the others
      logger.warn { "Unable to retrieve #{keys_for_server.size} elements from #{server.inspect}: #{e.message}"} if logger
    end
  end

  return results
rescue TypeError => err
  handle_error nil, err
end

#get_server_for_key(key, options = {}) ⇒ Object

Pick a server to handle the request based on a hash of the key.

Raises:

  • (ArgumentError)


661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
# File 'lib/memcache.rb', line 661

def get_server_for_key(key, options = {})
  raise ArgumentError, "illegal character in key #{key.inspect}" if
    key =~ /\s/
  raise ArgumentError, "key too long #{key.inspect}" if key.length > 250
  raise MemCacheError, "No servers available" if @servers.empty?
  return @servers.first if @servers.length == 1

  # for unknown reason hashing is different between memcache-client.rb and original Cache::Memcached.pm

  if @persistent_hashing
    hkey = Zlib.crc32 key

    20.times do |try|
      entryidx = Continuum.binary_search(@continuum, hkey)
      server = @continuum[entryidx].server
      return server if server.alive?
      break unless failover
      hkey = Zlib.crc32 "#{try}#{key}"
    end
  else
    hkey = (Zlib.crc32(key) >> 16) & 0x7fff

    20.times do |try|
      server = @buckets[hkey % @buckets.length]
      return server if server.alive?
      hkey += (Zlib.crc32("#{try}#{key}") >> 16) & 0x7fff 
    end
  end

  raise MemCacheError, "No servers available"
end

#gets(key, raw = nil) ⇒ Object



736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
# File 'lib/memcache.rb', line 736

def gets(key, raw = nil)
  with_server(key) do |server, cache_key|
    logger.debug { "gets #{key} from #{server.inspect}" } if logger
    result = with_socket_management(server) do |socket|
      socket.write "gets #{cache_key}\r\n"
      keyline = socket.gets # "VALUE <key> <flags> <bytes> <cas token>\r\n"

      if keyline.nil? then
        server.close
        raise MemCacheError, "lost connection to #{server.host}:#{server.port}"
      end

      raise_on_error_response! keyline
      return nil if keyline == "END\r\n"

      unless keyline =~ /(\d+) (\w+)\r/ then
        server.close
        raise MemCacheError, "unexpected response #{keyline.inspect}"
      end
      value = socket.read $1.to_i
      socket.read 2 # "\r\n"
      socket.gets   # "END\r\n"
      logger.debug { "gets #{key} from #{server.inspect}: #{value ? value.to_s.size : 'nil'}" } if logger
      [value, $2]
    end
    result[0] = Marshal.load result[0] unless (raw == nil && @raw) || raw
    result
  end
rescue TypeError => err
  handle_error nil, err
end

#handle_error(server, error) ⇒ Object

Handles error from server.



874
875
876
877
878
879
880
# File 'lib/memcache.rb', line 874

def handle_error(server, error)
  raise error if error.is_a?(MemCacheError)
  server.close if server
  new_error = MemCacheError.new error.message
  new_error.set_backtrace error.backtrace
  raise new_error
end

#incr(key, amount = 1) ⇒ Object

Increments the value for key by amount and returns the new value. key must already exist. If key is not an integer, it is assumed to be 0.



327
328
329
330
331
332
333
334
# File 'lib/memcache.rb', line 327

def incr(key, amount = 1)
  raise MemCacheError, "Update of readonly cache" if @readonly
  with_server(key) do |server, cache_key|
    cache_incr server, cache_key, amount
  end
rescue TypeError => err
  handle_error nil, err
end

#inspectObject

Returns a string representation of the cache object.



165
166
167
168
# File 'lib/memcache.rb', line 165

def inspect
  "<MemCache: %d servers, ns: %p, ro: %p, raw: %p>" %
    [@servers.length, @namespace, @readonly, @raw]
end

#make_cache_key(key) ⇒ Object

Create a key for the cache, incorporating the namespace qualifier if requested.



650
651
652
653
654
655
656
# File 'lib/memcache.rb', line 650

def make_cache_key(key)
  if namespace.nil? then
    key
  else
    "#{@namespace}:#{key}"
  end
end

#noreplyObject



882
883
884
# File 'lib/memcache.rb', line 882

def noreply
  @no_reply ? ' noreply' : ''
end

#prepend(key, value) ⇒ Object

Prepend - ‘add this data to an existing key before existing data’ Please note the value is always passed to memcached as raw since it doesn’t make a lot of sense to concatenate marshalled data together.

Raises:



486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
# File 'lib/memcache.rb', line 486

def prepend(key, value)
  raise MemCacheError, "Update of readonly cache" if @readonly
  with_server(key) do |server, cache_key|
    logger.debug { "prepend #{key} to #{server}: #{value ? value.to_s.size : 'nil'}" } if logger
    command = "prepend #{cache_key} 0 0 #{value.to_s.size}#{noreply}\r\n#{value}\r\n"

    with_socket_management(server) do |socket|
      socket.write command
      break nil if @no_reply
      result = socket.gets
      raise_on_error_response! result
      result
    end
  end
end

#raise_on_error_response!(response) ⇒ Object



897
898
899
900
901
# File 'lib/memcache.rb', line 897

def raise_on_error_response!(response)
  if response =~ /\A(?:CLIENT_|SERVER_)?ERROR(.*)/
    raise MemCacheError, $1.strip
  end
end

#readonly?Boolean

Returns whether or not the cache object was created read only.

Returns:

  • (Boolean)


180
181
182
# File 'lib/memcache.rb', line 180

def readonly?
  @readonly
end

#replace(key, value, expiry = 0, raw = false) ⇒ Object

Add key to the cache with value value that expires in expiry seconds, but only if key already exists in the cache. If raw is true, value will not be Marshalled.

Raises:



445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
# File 'lib/memcache.rb', line 445

def replace(key, value, expiry = 0, raw = false)
  raise MemCacheError, "Update of readonly cache" if @readonly
  with_server(key) do |server, cache_key|
    value = Marshal.dump value unless raw
    logger.debug { "replace #{key} to #{server}: #{value ? value.to_s.size : 'nil'}" } if logger
    command = "replace #{cache_key} 0 #{expiry} #{value.to_s.size}#{noreply}\r\n#{value}\r\n"

    with_socket_management(server) do |socket|
      socket.write command
      break nil if @no_reply
      result = socket.gets
      raise_on_error_response! result
      result
    end
  end
end

#request_setup(key) ⇒ Object

Performs setup for making a request with key from memcached. Returns the server to fetch the key from and the complete key to use.

Raises:



890
891
892
893
894
895
# File 'lib/memcache.rb', line 890

def request_setup(key)
  raise MemCacheError, 'No active servers' unless active?
  cache_key = make_cache_key key
  server = get_server_for_key cache_key
  return server, cache_key
end

#resetObject

Reset the connection to all memcache servers. This should be called if there is a problem with a cache lookup that might have left the connection in a corrupted state.



555
556
557
# File 'lib/memcache.rb', line 555

def reset
  @servers.each { |server| server.close }
end

#set(key, value, expiry = 0, raw = nil) ⇒ Object

Raises:



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
# File 'lib/memcache.rb', line 345

def set(key, value, expiry = 0, raw = nil)
  raise MemCacheError, "Update of readonly cache" if @readonly
  with_server(key) do |server, cache_key|

    value = Marshal.dump value unless  (raw == nil && @raw) || raw
    logger.debug { "set #{key} to #{server.inspect}: #{value.to_s.size}" } if logger

    raise MemCacheError, "Value too large, memcached can only store 1MB of data per key" if value.to_s.size > ONE_MB

    command = "set #{cache_key} 0 #{expiry} #{value.to_s.size}#{noreply}\r\n#{value}\r\n"

    with_socket_management(server) do |socket|
      socket.write command
      break nil if @no_reply
      result = socket.gets
      raise_on_error_response! result

      if result.nil?
        server.close
        raise MemCacheError, "lost connection to #{server.host}:#{server.port}"
      end

      result
    end
  end
end

#statsObject

Returns statistics for each memcached server. An explanation of the statistics can be found in the memcached docs:

code.sixapart.com/svn/memcached/trunk/server/doc/protocol.txt

Example:

>> pp CACHE.stats
{"localhost:11211"=>
  {"bytes"=>4718,
   "pid"=>20188,
   "connection_structures"=>4,
   "time"=>1162278121,
   "pointer_size"=>32,
   "limit_maxbytes"=>67108864,
   "cmd_get"=>14532,
   "version"=>"1.2.0",
   "bytes_written"=>432583,
   "cmd_set"=>32,
   "get_misses"=>0,
   "total_connections"=>19,
   "curr_connections"=>3,
   "curr_items"=>4,
   "uptime"=>1557,
   "get_hits"=>14532,
   "total_items"=>32,
   "rusage_system"=>0.313952,
   "rusage_user"=>0.119981,
   "bytes_read"=>190619}}
=> nil

Raises:



591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
# File 'lib/memcache.rb', line 591

def stats
  raise MemCacheError, "No active servers" unless active?
  server_stats = {}

  @servers.each do |server|
    next unless server.alive?

    with_socket_management(server) do |socket|
      value = nil
      socket.write "stats\r\n"
      stats = {}
      while line = socket.gets do
        raise_on_error_response! line
        break if line == "END\r\n"
        if line =~ /\ASTAT ([\S]+) ([\w\.\:]+)/ then
          name, value = $1, $2
          stats[name] = case name
                        when 'version'
                          value
                        when 'rusage_user', 'rusage_system' then
                          seconds, microseconds = value.split(/:/, 2)
                          microseconds ||= 0
                          Float(seconds) + (Float(microseconds) / 1_000_000)
                        else
                          if value =~ /\A\d+\Z/ then
                            value.to_i
                          else
                            value
                          end
                        end
        end
      end
      server_stats["#{server.host}:#{server.port}"] = stats
    end
  end

  raise MemCacheError, "No active servers" if server_stats.empty?
  server_stats
end

#with_server(key) ⇒ Object



855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
# File 'lib/memcache.rb', line 855

def with_server(key)
  retried = false
  begin
    server, cache_key = request_setup(key)
    yield server, cache_key
  rescue IndexError => e
    logger.warn { "Server failed: #{e.class.name}: #{e.message}" } if logger
    if !retried && @servers.size > 1
      logger.info { "Connection to server #{server.inspect} DIED! Retrying operation..." } if logger
      retried = true
      retry
    end
    handle_error(nil, e)
  end
end

#with_socket_management(server, &block) ⇒ Object

Gets or creates a socket connected to the given server, and yields it to the block, wrapped in a mutex synchronization if @multithread is true.

If a socket error (SocketError, SystemCallError, IOError) or protocol error (MemCacheError) is raised by the block, closes the socket, attempts to connect again, and retries the block (once). If an error is again raised, reraises it as MemCacheError.

If unable to connect to the server (or if in the reconnect wait period), raises MemCacheError. Note that the socket connect code marks a server dead for a timeout period, so retrying does not apply to connection attempt failures (but does still apply to unexpectedly lost connections etc.).



825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
# File 'lib/memcache.rb', line 825

def with_socket_management(server, &block)

  @mutex.lock if @multithread
  retried = false

  begin
    socket = server.socket

    # Raise an IndexError to show this server is out of whack. If were inside
    # a with_server block, we'll catch it and attempt to restart the operation.

    raise IndexError, "No connection to server (#{server.status})" if socket.nil?

    block.call(socket)

  rescue SocketError, Errno::EAGAIN, Timeout::Error => err
    logger.warn { "Socket failure: #{err.message}" } if logger
    server.mark_dead(err)
    handle_error(server, err)

  rescue MemCacheError, SystemCallError, IOError => err
    logger.warn { "Generic failure: #{err.class.name}: #{err.message}" } if logger
    handle_error(server, err) if retried || socket.nil?
    retried = true
    retry
  end
ensure
  @mutex.unlock if @multithread
end