Class: Memcache

Inherits:
Memcached show all
Defined in:
lib/hybrid_memcache.rb

Constant Summary collapse

WRITE_LOCK_WAIT = 
1
LOCK_TIMEOUT = 
5

Instance Method Summary collapse

Constructor Details

#initialize(opts = {}) ⇒ Memcache

Returns a new instance of Memcache.



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# File 'lib/hybrid_memcache.rb', line 7

def initialize (opts={})
  servers    = opts[:servers] && opts.delete(:servers)
  @namespace = ""
  
  super(servers, {
    :prefix_key           =>  '',
    :prefix_delimiter     =>  '',
    :support_cas          => true,
    
    :hash                 => :fnv1_32,
    :distribution         => :consistent_ketama,
    :ketama_weighted      => true,
    :server_failure_limit => 2,
    :retry_timeout        => 30,
    
    :default_ttl          => 604800,
  }.merge!(opts))
end

Instance Method Details

#[](key) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 324

def [](key)
  get(key)
end

#[]=(key, value) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 329

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

#add(key, value, opts = {}) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 34

def add(key, value, opts={})
  super(normalize_keys(key), value, *opts_to_params(opts))
  return value
rescue Memcached::NotStored
  return nil
end

#append(key, value) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 197

def append(key, value)
  super(normalize_keys(key), value)
  return true
rescue Memcached::NotStored
  return false
end

#cas(key, value, opts = {}) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 175

def cas(key, value, opts={})
  ttl, marshal, flags = opts_to_params(opts)
  key  = normalize_keys(key)
  data = marshal ? Marshal.dump(value) : value

  check_return_code(Lib.memcached_cas(@struct, key, data, ttl, flags, opts[:cas]), key)
  value.memcache_cas   = @struct.result.cas
  value.memcache_flags = @struct.result.flags
  return value
rescue Memcached::NotStored
 return nil
end

#clone ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 27

def clone
   klone = self.class.new({ :servers => servers }.merge(options))
   klone.set_namespace @namespace
   klone
end

#count(key) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 205

def count(key)
  get(key, :raw => true).to_i
end

#decrement(key, amount = 1) ⇒ Object Also known as: decr 



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# File 'lib/hybrid_memcache.rb', line 218

def decrement(key, amount=1)
  super(normalize_keys(key), amount)
rescue Memcached::NotFound
  return nil
end

#delete(key) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 310

def delete(key)
  super(normalize_keys(key))
  return true
rescue Memcached::NotFound
  return nil
end

#flush_all(opts = {}) ⇒ Object Also known as: clear 



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# File 'lib/hybrid_memcache.rb', line 318

def flush_all(opts={})
  flush
end

#get(keys, opts = {}) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 71

def get(keys, opts={})
  marshal = !opts[:raw]
  cas     =  opts[:cas]
  
  unless keys.is_a?(Array)
    ## ninjudd-memcache has a weird behaviour where get can be called with an
    ## expiry and that will transform the get into get+cas. this in turn has
    ## the effect of extending the expiry of the object. 
    if opts[:expiry]
      value = get(keys,        :cas => true)
      value = cas(keys, value, :cas => value.memcache_cas, :expiry => opts[:expiry])
      return value
    end
    
    ## Single get
    value, flags, ret = Lib.memcached_get_rvalue(@struct, normalize_keys(keys))
    
    ## ninjudd-memcache treats broken servers as cache missis, so return nil
    ## check_return_code(ret, keys)
    return nil unless ret == 0
    
    if marshal
      value = Marshal.load(value) 
    end

    value.memcache_cas   = cas ? @struct.result.cas : false
    value.memcache_flags = flags
    return value
  else
    ## Multi get
    return {} if keys.empty?

    ## ninjudd-memcache normalizes keys into the form namespace:index:key
    ## but it hides this form from the caller, so the caller expects to 
    ## get a hash with the keys in their denormalized form. That's what
    ## the norm_to_std hash is all about. 
    normalized  = normalize_keys(keys)
    norm_to_std = {}
    
    ## but note, the keys have to be transformed into strings, even if they
    ## started out as fixnums
    keys.each_with_index {|k,idx| norm_to_std[normalized[idx]] = keys[idx].to_s }
    
    ret = Lib.memcached_mget(@struct, normalized)
    
    ## once again: potentiall braken server == cache miss
    ## check_return_code(ret, normalized)
    return {} unless ret == 0
  
    hash = {}
    keys.each do
      value, key, flags, ret = Lib.memcached_fetch_rvalue(@struct)
      if ret == Lib::MEMCACHED_END
        break 
      end
      
      if ret != 0 
        ## once again: potentiall braken server == cache miss
        ## check_return_code(ret, key) 
        value = nil 
      else  
        # Assign the value
        if marshal
          value = Marshal.load(value) 
        end 
        value.memcache_cas   = cas ? @struct.result.cas : false
        value.memcache_flags = flags
      end
      
      hash[ norm_to_std[key] ] = value
    end
    return hash
  end
rescue Memcached::NotFound
  return nil
end

#get_or_add(key, *args) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 235

def get_or_add(key, *args)
  if block_given?
    opts = args[0] || {}
    get(key) || add(key, yield,   opts) || get(key)
  else
    opts = args[1] || {}
    get(key) || add(key, args[0], opts) || get(key)
  end
end

#get_or_set(key, *args) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 246

def get_or_set(key, *args)
  if block_given?
    opts = args[0] || {}
    get(key) || set(key, yield,   opts) || get(key)
  else
    opts = args[1] || {}
    get(key) || set(key, args[0], opts) || get(key)
  end
end

#get_some(keys, opts = {}) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 257

def get_some(keys, opts = {})
  keys    = keys.collect { |k| k.to_s }
  records = opts[:disable] ? {} : self.get(keys, opts)
  
  if opts[:validation]
    records.delete_if do |key, value|
      not opts[:validation].call(key, value)
    end
  end
  
  keys_to_fetch = keys - records.keys
  method        = opts[:overwrite] ? :set : :add
  if keys_to_fetch.any?
    yield(keys_to_fetch).each do |key, value|
      self.send(method, key, value, opts) unless opts[:disable] or opts[:disable_write]
      records[key] = value
    end
  end
  records
end

#in_namespace(ns) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 47

def in_namespace(ns)
  # Temporarily change the namespace for convenience.
  begin
    old_namespace = @namespace
    self.set_namespace("#{old_namespace}#{ns}")
    yield
  ensure
    self.set_namespace(old_namespace)
  end
end

#increment(key, amount = 1) ⇒ Object Also known as: incr 



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# File 'lib/hybrid_memcache.rb', line 210

def increment(key, amount=1)
  super(normalize_keys(key), amount)
rescue Memcached::NotFound
  return nil
end

#inspect ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 42

def inspect
  "<Memcache: %d servers, ns: %p" % [ servers.length, namespace ]
end

#lock(key, opts = {}) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 284

def lock(key, opts={})
  expiry = opts[:expiry] || LOCK_TIMEOUT
  add(lock_key(key), Socket.gethostname, :expiry => expiry, :raw => true)
end

#lock_key(key) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 279

def lock_key(key)
  "lock:#{key}"
end

#locked?(key) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/hybrid_memcache.rb', line 305

def locked?(key)
  get(lock_key(key), :raw => true)
end

#namespace ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 59

def namespace 
  @namespace
end

#normalize_keys(keys) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 334

def normalize_keys (keys)
  ns = @namespace.nil? || @namespace.size == 0 ? "" : "#{@namespace}:"
  
  unless keys.is_a?(Array) 
    k = "#{ns}#{keys}"
    k.gsub!(/%/, '%%') if k.include?('%')
    k.gsub!(/ /, '%s') if k.include?(' ')
    return k
  else
    return keys.collect do |k| 
      k = "#{ns}#{k}" 
      k.gsub!(/%/, '%%') if k.include?('%')
      k.gsub!(/ /, '%s') if k.include?(' ')
      k
    end
  end
end

#opts_to_params(opts = {}) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 353

def opts_to_params (opts={})
  ## - if no :expiry, use @default_ttl
  ## - fauna-memcached uses marshal which has the opposite meaning of 
  ##   ninjudd's :raw. that is, :raw means DO NOT marshal, so invert
  ##   :raw via ! ... 
  ## - if no :flags,  use FLAGS
  return  opts[:expiry] || @default_ttl,
         !opts[:raw],
          opts[:flags]  || FLAGS
end

#prepend(key, value) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 189

def prepend(key,value)
  super(normalize_keys(key), value)
  return true
rescue Memcached::NotStored
  return false
end

#read(keys, opts = {}) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 149

def read(keys, opts={})
  get(keys, opts.merge(:raw => true))
end

#replace(key, value, opts = {}) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 167

def replace(key, value, opts={})
  super(normalize_keys(key), value, *opts_to_params(opts))
  return value
rescue Memcached::NotStored
  return nil
end

#set(key, value, opts = {}) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 154

def set(key, value, opts={})
  super(normalize_keys(key), value, *opts_to_params(opts))
  return value
rescue Memcached::NotFound
  return nil
end

#set_namespace(ns) ⇒ Object Also known as: namespace=, set_namespace= 



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# File 'lib/hybrid_memcache.rb', line 64

def set_namespace(ns)
  @namespace = ns
end

#unlock(key) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 290

def unlock(key)
  delete(lock_key(key))
end

#update(key, opts = {}) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 226

def update(key, opts={})
  if value = get(key, :cas => true)
    cas(key, yield(value), opts.merge!(:cas => value.memcache_cas))
  else
    add(key, yield(value), opts)
  end
end

#with_lock(key, opts = {}) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 295

def with_lock(key, opts={})
  until lock(key) do
    return if opts[:ignore]
    sleep(WRITE_LOCK_WAIT)
  end
  yield
  unlock(key) unless opts[:keep]
end

#write(key, value, opts = {}) ⇒ Object 



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# File 'lib/hybrid_memcache.rb', line 162

def write(key, value, opts={})
  set(key, value, opts.merge(:raw => true))
end