Moved the caching stores from ActionController::Caching::Fragments::* to ActiveSupport::Cache::*. If you're explicitly referring to a store, like ActionController::Caching::Fragments::MemoryStore, you need to update that reference with ActiveSupport::Cache::MemoryStore [DHH] Deprecated ActionController::Base.fragment_cache_store for ActionController::Base.cache_store [DHH] All fragment cache keys are now by default prefixed with the 'views/' namespace [DHH] Added ActiveRecord::Base.cache_key to make it easier to cache Active Records in combination with the new ActiveSupport::Cache::* libraries [DHH] Added ActiveSupport::Gzip.decompress/compress(source) as an easy wrapper for Zlib [Tobias Luetke] Included MemCache-Client to make the improved ActiveSupport::Cache::MemCacheStore work out of the box [Bob Cottrell, Eric Hodel] Added config.cache_store to environment options to control the default cache store (default is FileStore if tmp/cache is present, otherwise MemoryStore is used) [DHH]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@8546 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

1 files changed, 832 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/vendor/memcache-client-1.5.0/memcache.rb b/activesupport/lib/active_support/vendor/memcache-client-1.5.0/memcache.rb
new file mode 100644
index 0000000000..8c01b2e89d
--- /dev/null
+++ b/activesupport/lib/active_support/vendor/memcache-client-1.5.0/memcache.rb
@@ -0,0 +1,832 @@
+# All original code copyright 2005, 2006, 2007 Bob Cottrell, Eric Hodel,
+# The Robot Co-op.  All rights reserved.
+# 
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+# 3. Neither the names of the authors nor the names of their contributors
+#    may be used to endorse or promote products derived from this software
+#    without specific prior written permission.
+# 
+# THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS
+# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
+# OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
+# OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
+# BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+# WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+# OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+# EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+require 'socket'
+require 'thread'
+require 'timeout'
+require 'rubygems'
+
+class String
+
+  ##
+  # Uses the ITU-T polynomial in the CRC32 algorithm.
+
+  def crc32_ITU_T
+    n = length
+    r = 0xFFFFFFFF
+
+    n.times do |i|
+      r ^= self[i]
+      8.times do
+        if (r & 1) != 0 then
+          r = (r>>1) ^ 0xEDB88320
+        else
+          r >>= 1
+        end
+      end
+    end
+
+    r ^ 0xFFFFFFFF
+  end
+
+end
+
+##
+# A Ruby client library for memcached.
+#
+# This is intended to provide access to basic memcached functionality.  It
+# does not attempt to be complete implementation of the entire API, but it is
+# approaching a complete implementation.
+
+class MemCache
+
+  ##
+  # The version of MemCache you are using.
+
+  VERSION = '1.5.0'
+
+  ##
+  # Default options for the cache object.
+
+  DEFAULT_OPTIONS = {
+    :namespace   => nil,
+    :readonly    => false,
+    :multithread => false,
+  }
+
+  ##
+  # Default memcached port.
+
+  DEFAULT_PORT = 11211
+
+  ##
+  # Default memcached server weight.
+
+  DEFAULT_WEIGHT = 1
+
+  ##
+  # The amount of time to wait for a response from a memcached server.  If a
+  # response is not completed within this time, the connection to the server
+  # will be closed and an error will be raised.
+
+  attr_accessor :request_timeout
+
+  ##
+  # The namespace for this instance
+
+  attr_reader :namespace
+
+  ##
+  # The multithread setting for this instance
+
+  attr_reader :multithread
+
+  ##
+  # The servers this client talks to.  Play at your own peril.
+
+  attr_reader :servers
+
+  ##
+  # 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 exeception on cache writes when true.
+  #   [:multithread] Wraps cache access in a Mutex for thread safety.
+  #
+  # Other options are ignored.
+
+  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]
+    @mutex       = Mutex.new if @multithread
+    @buckets     = []
+    self.servers = servers
+  end
+
+  ##
+  # Returns a string representation of the cache object.
+
+  def inspect
+    "<MemCache: %d servers, %d buckets, ns: %p, ro: %p>" %
+      [@servers.length, @buckets.length, @namespace, @readonly]
+  end
+
+  ##
+  # Returns whether there is at least one active server for the object.
+
+  def active?
+    not @servers.empty?
+  end
+
+  ##
+  # Returns whether or not the cache object was created read only.
+
+  def readonly?
+    @readonly
+  end
+
+  ##
+  # Set the servers that the requests will be distributed between.  Entries
+  # can be either strings of the form "hostname:port" or
+  # "hostname:port:weight" or MemCache::Server objects.
+
+  def servers=(servers)
+    # Create the server objects.
+    @servers = servers.collect do |server|
+      case server
+      when String
+        host, port, weight = server.split ':', 3
+        port ||= DEFAULT_PORT
+        weight ||= DEFAULT_WEIGHT
+        Server.new self, host, port, weight
+      when Server
+        if server.memcache.multithread != @multithread then
+          raise ArgumentError, "can't mix threaded and non-threaded servers"
+        end
+        server
+      else
+        raise TypeError, "cannot convert #{server.class} into MemCache::Server"
+      end
+    end
+
+    # Create an array of server buckets for weight selection of servers.
+    @buckets = []
+    @servers.each do |server|
+      server.weight.times { @buckets.push(server) }
+    end
+  end
+
+  ##
+  # Deceremets 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.  +key+ can not be decremented below 0.
+
+  def decr(key, amount = 1)
+    server, cache_key = request_setup key
+
+    if @multithread then
+      threadsafe_cache_decr server, cache_key, amount
+    else
+      cache_decr server, cache_key, amount
+    end
+  rescue TypeError, SocketError, SystemCallError, IOError => err
+    handle_error server, err
+  end
+
+  ##
+  # Retrieves +key+ from memcache.  If +raw+ is false, the value will be
+  # unmarshalled.
+
+  def get(key, raw = false)
+    server, cache_key = request_setup key
+
+    value = if @multithread then
+              threadsafe_cache_get server, cache_key
+            else
+              cache_get server, cache_key
+            end
+
+    return nil if value.nil?
+
+    value = Marshal.load value unless raw
+
+    return value
+  rescue TypeError, SocketError, SystemCallError, IOError => err
+    handle_error server, err
+  end
+
+  ##
+  # 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 }
+
+  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|
+      keys = keys.join ' '
+      values = if @multithread then
+                 threadsafe_cache_get_multi server, keys
+               else
+                 cache_get_multi server, keys
+               end
+      values.each do |key, value|
+        results[cache_keys[key]] = Marshal.load value
+      end
+    end
+
+    return results
+  rescue TypeError, SocketError, SystemCallError, IOError => err
+    handle_error server, err
+  end
+
+  ##
+  # Increments the value for +key+ by +amount+ and retruns the new value.
+  # +key+ must already exist.  If +key+ is not an integer, it is assumed to be
+  # 0.
+
+  def incr(key, amount = 1)
+    server, cache_key = request_setup key
+
+    if @multithread then
+      threadsafe_cache_incr server, cache_key, amount
+    else
+      cache_incr server, cache_key, amount
+    end
+  rescue TypeError, SocketError, SystemCallError, IOError => err
+    handle_error server, err
+  end
+
+  ##
+  # 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.
+
+  def set(key, value, expiry = 0, raw = false)
+    raise MemCacheError, "Update of readonly cache" if @readonly
+    server, cache_key = request_setup key
+    socket = server.socket
+
+    value = Marshal.dump value unless raw
+    command = "set #{cache_key} 0 #{expiry} #{value.size}\r\n#{value}\r\n"
+
+    begin
+      @mutex.lock if @multithread
+      socket.write command
+      result = socket.gets
+      raise MemCacheError, $1.strip if result =~ /^SERVER_ERROR (.*)/
+    rescue SocketError, SystemCallError, IOError => err
+      server.close
+      raise MemCacheError, err.message
+    ensure
+      @mutex.unlock if @multithread
+    end
+  end
+
+  ##
+  # 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 or MemCache#[]=.
+
+  def add(key, value, expiry = 0, raw = false)
+    raise MemCacheError, "Update of readonly cache" if @readonly
+    server, cache_key = request_setup key
+    socket = server.socket
+
+    value = Marshal.dump value unless raw
+    command = "add #{cache_key} 0 #{expiry} #{value.size}\r\n#{value}\r\n"
+
+    begin
+      @mutex.lock if @multithread
+      socket.write command
+      socket.gets
+    rescue SocketError, SystemCallError, IOError => err
+      server.close
+      raise MemCacheError, err.message
+    ensure
+      @mutex.unlock if @multithread
+    end
+  end
+
+  ##
+  # Removes +key+ from the cache in +expiry+ seconds.
+
+  def delete(key, expiry = 0)
+    @mutex.lock if @multithread
+
+    raise MemCacheError, "No active servers" unless active?
+    cache_key = make_cache_key key
+    server = get_server_for_key cache_key
+
+    sock = server.socket
+    raise MemCacheError, "No connection to server" if sock.nil?
+
+    begin
+      sock.write "delete #{cache_key} #{expiry}\r\n"
+      sock.gets
+    rescue SocketError, SystemCallError, IOError => err
+      server.close
+      raise MemCacheError, err.message
+    end
+  ensure
+    @mutex.unlock if @multithread
+  end
+
+  ##
+  # Flush the cache from all memcache servers.
+
+  def flush_all
+    raise MemCacheError, 'No active servers' unless active?
+    raise MemCacheError, "Update of readonly cache" if @readonly
+    begin
+      @mutex.lock if @multithread
+      @servers.each do |server|
+        begin
+          sock = server.socket
+          raise MemCacheError, "No connection to server" if sock.nil?
+          sock.write "flush_all\r\n"
+          result = sock.gets
+          raise MemCacheError, $2.strip if result =~ /^(SERVER_)?ERROR(.*)/
+        rescue SocketError, SystemCallError, IOError => err
+          server.close
+          raise MemCacheError, err.message
+        end
+      end
+    ensure
+      @mutex.unlock if @multithread
+    end
+  end
+
+  ##
+  # 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.
+
+  def reset
+    @servers.each { |server| server.close }
+  end
+
+  ##
+  # Returns statistics for each memcached server.  An explanation of the
+  # statistics can be found in the memcached docs:
+  #
+  # http://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
+
+  def stats
+    raise MemCacheError, "No active servers" unless active?
+    server_stats = {}
+
+    @servers.each do |server|
+      sock = server.socket
+      raise MemCacheError, "No connection to server" if sock.nil?
+
+      value = nil
+      begin
+        sock.write "stats\r\n"
+        stats = {}
+        while line = sock.gets do
+          break if line == "END\r\n"
+          if line =~ /^STAT ([\w]+) ([\w\.\:]+)/ then
+            name, value = $1, $2
+            stats[name] = case name
+                          when 'version'
+                            value
+                          when 'rusage_user', 'rusage_system' then
+                            seconds, microseconds = value.split(/:/, 2)
+                            microseconds ||= 0
+                            Float(seconds) + (Float(microseconds) / 1_000_000)
+                          else
+                            if value =~ /^\d+$/ then
+                              value.to_i
+                            else
+                              value
+                            end
+                          end
+          end
+        end
+        server_stats["#{server.host}:#{server.port}"] = stats
+      rescue SocketError, SystemCallError, IOError => err
+        server.close
+        raise MemCacheError, err.message
+      end
+    end
+
+    server_stats
+  end
+
+  ##
+  # Shortcut to get a value from the cache.
+
+  alias [] get
+
+  ##
+  # 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.
+
+  def []=(key, value)
+    set key, value
+  end
+
+  protected
+
+  ##
+  # Create a key for the cache, incorporating the namespace qualifier if
+  # requested.
+
+  def make_cache_key(key)
+    if namespace.nil? then
+      key
+    else
+      "#{@namespace}:#{key}"
+    end
+  end
+
+  ##
+  # Pick a server to handle the request based on a hash of the key.
+
+  def get_server_for_key(key)
+    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
+
+    hkey = hash_for key
+
+    20.times do |try|
+      server = @buckets[hkey % @buckets.nitems]
+      return server if server.alive?
+      hkey += hash_for "#{try}#{key}"
+    end
+
+    raise MemCacheError, "No servers available"
+  end
+
+  ##
+  # Returns an interoperable hash value for +key+.  (I think, docs are
+  # sketchy for down servers).
+
+  def hash_for(key)
+    (key.crc32_ITU_T >> 16) & 0x7fff
+  end
+
+  ##
+  # Performs a raw decr for +cache_key+ from +server+.  Returns nil if not
+  # found.
+
+  def cache_decr(server, cache_key, amount)
+    socket = server.socket
+    socket.write "decr #{cache_key} #{amount}\r\n"
+    text = socket.gets
+    return nil if text == "NOT_FOUND\r\n"
+    return text.to_i
+  end
+
+  ##
+  # Fetches the raw data for +cache_key+ from +server+.  Returns nil on cache
+  # miss.
+
+  def cache_get(server, cache_key)
+    socket = server.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
+
+    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
+
+  ##
+  # Fetches +cache_keys+ from +server+ using a multi-get.
+
+  def cache_get_multi(server, cache_keys)
+    values = {}
+    socket = server.socket
+    socket.write "get #{cache_keys}\r\n"
+
+    while keyline = socket.gets do
+      return values if keyline == "END\r\n"
+
+      unless keyline =~ /^VALUE (.+) (.+) (.+)/ 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}"
+  end
+
+  ##
+  # Performs a raw incr for +cache_key+ from +server+.  Returns nil if not
+  # found.
+
+  def cache_incr(server, cache_key, amount)
+    socket = server.socket
+    socket.write "incr #{cache_key} #{amount}\r\n"
+    text = socket.gets
+    return nil if text == "NOT_FOUND\r\n"
+    return text.to_i
+  end
+
+  ##
+  # Handles +error+ from +server+.
+
+  def handle_error(server, error)
+    server.close if server
+    new_error = MemCacheError.new error.message
+    new_error.set_backtrace error.backtrace
+    raise new_error
+  end
+
+  ##
+  # Performs setup for making a request with +key+ from memcached.  Returns
+  # the server to fetch the key from and the complete key to use.
+
+  def request_setup(key)
+    raise MemCacheError, 'No active servers' unless active?
+    cache_key = make_cache_key key
+    server = get_server_for_key cache_key
+    raise MemCacheError, 'No connection to server' if server.socket.nil?
+    return server, cache_key
+  end
+
+  def threadsafe_cache_decr(server, cache_key, amount) # :nodoc:
+    @mutex.lock
+    cache_decr server, cache_key, amount
+  ensure
+    @mutex.unlock
+  end
+
+  def threadsafe_cache_get(server, cache_key) # :nodoc:
+    @mutex.lock
+    cache_get server, cache_key
+  ensure
+    @mutex.unlock
+  end
+
+  def threadsafe_cache_get_multi(socket, cache_keys) # :nodoc:
+    @mutex.lock
+    cache_get_multi socket, cache_keys
+  ensure
+    @mutex.unlock
+  end
+
+  def threadsafe_cache_incr(server, cache_key, amount) # :nodoc:
+    @mutex.lock
+    cache_incr server, cache_key, amount
+  ensure
+    @mutex.unlock
+  end
+
+  ##
+  # This class represents a memcached server instance.
+
+  class Server
+
+    ##
+    # The amount of time to wait to establish a connection with a memcached
+    # server.  If a connection cannot be established within this time limit,
+    # the server will be marked as down.
+
+    CONNECT_TIMEOUT = 0.25
+
+    ##
+    # The amount of time to wait before attempting to re-establish a
+    # connection with a server that is marked dead.
+
+    RETRY_DELAY = 30.0
+
+    ##
+    # The host the memcached server is running on.
+
+    attr_reader :host
+
+    ##
+    # The port the memcached server is listening on.
+
+    attr_reader :port
+
+    ##
+    # The weight given to the server.
+
+    attr_reader :weight
+
+    ##
+    # The time of next retry if the connection is dead.
+
+    attr_reader :retry
+
+    ##
+    # A text status string describing the state of the server.
+
+    attr_reader :status
+
+    ##
+    # Create a new MemCache::Server object for the memcached instance
+    # listening on the given host and port, weighted by the given weight.
+
+    def initialize(memcache, host, port = DEFAULT_PORT, weight = DEFAULT_WEIGHT)
+      raise ArgumentError, "No host specified" if host.nil? or host.empty?
+      raise ArgumentError, "No port specified" if port.nil? or port.to_i.zero?
+
+      @memcache = memcache
+      @host   = host
+      @port   = port.to_i
+      @weight = weight.to_i
+
+      @multithread = @memcache.multithread
+      @mutex = Mutex.new
+
+      @sock   = nil
+      @retry  = nil
+      @status = 'NOT CONNECTED'
+    end
+
+    ##
+    # Return a string representation of the server object.
+
+    def inspect
+      "<MemCache::Server: %s:%d [%d] (%s)>" % [@host, @port, @weight, @status]
+    end
+
+    ##
+    # Check whether the server connection is alive.  This will cause the
+    # socket to attempt to connect if it isn't already connected and or if
+    # the server was previously marked as down and the retry time has
+    # been exceeded.
+
+    def alive?
+      !!socket
+    end
+
+    ##
+    # Try to connect to the memcached server targeted by this object.
+    # Returns the connected socket object on success or nil on failure.
+
+    def socket
+      @mutex.lock if @multithread
+      return @sock if @sock and not @sock.closed?
+
+      @sock = nil
+
+      # If the host was dead, don't retry for a while.
+      return if @retry and @retry > Time.now
+
+      # Attempt to connect if not already connected.
+      begin
+        @sock = timeout CONNECT_TIMEOUT do
+          TCPSocket.new @host, @port
+        end
+        if Socket.constants.include? 'TCP_NODELAY' then
+          @sock.setsockopt Socket::IPPROTO_TCP, Socket::TCP_NODELAY, 1
+        end
+        @retry  = nil
+        @status = 'CONNECTED'
+      rescue SocketError, SystemCallError, IOError, Timeout::Error => err
+        mark_dead err.message
+      end
+
+      return @sock
+    ensure
+      @mutex.unlock if @multithread
+    end
+
+    ##
+    # Close the connection to the memcached server targeted by this
+    # object.  The server is not considered dead.
+
+    def close
+      @mutex.lock if @multithread
+      @sock.close if @sock && !@sock.closed?
+      @sock   = nil
+      @retry  = nil
+      @status = "NOT CONNECTED"
+    ensure
+      @mutex.unlock if @multithread
+    end
+
+    private
+
+    ##
+    # Mark the server as dead and close its socket.
+
+    def mark_dead(reason = "Unknown error")
+      @sock.close if @sock && !@sock.closed?
+      @sock   = nil
+      @retry  = Time.now + RETRY_DELAY
+
+      @status = sprintf "DEAD: %s, will retry at %s", reason, @retry
+    end
+
+  end
+
+  ##
+  # Base MemCache exception class.
+
+  class MemCacheError < RuntimeError; end
+
+end
+