Class: Dalli::Client

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

Overview

Dalli::Client is the main class which developers will use to interact with Memcached.

Constant Summary collapse

ALLOWED_STAT_KEYS = 
i[items slabs settings].freeze
CACHE_NILS = 
{ cache_nils: true }.freeze

Instance Method Summary collapse

Constructor Details

#initialize(servers = nil, options = {}) ⇒ Client

Dalli::Client is the main class which developers will use to interact with the memcached server. Usage:

Dalli::Client.new(['localhost:11211:10',
                   'cache-2.example.com:11211:5',
                   '192.168.0.1:22122:5',
                   '/var/run/memcached/socket'],
                  failover: true, expires_in: 300)

servers is an Array of “host:port:weight” where weight allows you to distribute cache unevenly. Both weight and port are optional. If you pass in nil, Dalli will use the MEMCACHE_SERVERS environment variable or default to ‘localhost:11211’ if it is not present. Dalli also supports the ability to connect to Memcached on localhost through a UNIX socket. To use this functionality, use a full pathname (beginning with a slash character ‘/’) in place of the “host:port” pair in the server configuration.

Options:

  • :namespace - prepend each key with this value to provide simple namespacing.

  • :failover - if a server is down, look for and store values on another server in the ring. Default: true.

  • :threadsafe - ensure that only one thread is actively using a socket at a time. Default: true.

  • :expires_in - default TTL in seconds if you do not pass TTL as a parameter to an individual operation, defaults

    to 0 or forever.

  • :compress - if true Dalli will compress values larger than compression_min_size bytes before sending them

    to memcached.  Default: true.

  • :compression_min_size - the minimum size (in bytes) for which Dalli will compress values sent to Memcached.

    Defaults to 4K.

  • :serializer - defaults to Marshal

  • :compressor - defaults to Dalli::Compressor, a Zlib-based implementation

  • :cache_nils - defaults to false, if true Dalli will not treat cached nil values as ‘not found’ for

    #fetch operations.

  • :digest_class - defaults to Digest::MD5, allows you to pass in an object that responds to the hexdigest method,

    useful for injecting a FIPS compliant hash object.

  • :protocol_implementation - defaults to Dalli::Protocol::Binary which uses the binary protocol. Allows you to

    pass an alternative implementation using another protocol.



49
50
51
52
53
54
 
# File 'lib/dalli/client.rb', line 49

def initialize(servers = nil, options = {})
  @servers = ::Dalli::ServersArgNormalizer.normalize_servers(servers)
  @options = normalize_options(options)
  @key_manager = ::Dalli::KeyManager.new(@options)
  @ring = nil
end

Instance Method Details

#add(key, value, ttl = nil, req_options = nil) ⇒ Object

Conditionally add a key/value pair, if the key does not already exist on the server. Returns truthy if the operation succeeded.



216
217
218
 
# File 'lib/dalli/client.rb', line 216

def add(key, value, ttl = nil, req_options = nil)
  perform(:add, key, value, ttl_or_default(ttl), req_options)
end

#alive! ⇒ Object

Make sure memcache servers are alive, or raise an Dalli::RingError



344
345
346
 
# File 'lib/dalli/client.rb', line 344

def alive!
  ring.server_for_key('')
end

#append(key, value) ⇒ Object

Append value to the value already stored on the server for ‘key’. Appending only works for values stored with :raw => true.



248
249
250
 
# File 'lib/dalli/client.rb', line 248

def append(key, value)
  perform(:append, key, value.to_s)
end

#cache_nils ⇒ Object 



363
364
365
 
# File 'lib/dalli/client.rb', line 363

def cache_nils
  @options[:cache_nils]
end

#cas(key, ttl = nil, req_options = nil, &block) ⇒ Object

compare and swap values using optimistic locking. Fetch the existing value for key. If it exists, yield the value to the block. Add the block’s return value as the new value for the key. Add will fail if someone else changed the value.

Returns:

  • nil if the key did not exist.

  • false if the value was changed by someone else.

  • true if the value was successfully updated.



160
161
162
 
# File 'lib/dalli/client.rb', line 160

def cas(key, ttl = nil, req_options = nil, &block)
  cas_core(key, false, ttl, req_options, &block)
end

#cas!(key, ttl = nil, req_options = nil, &block) ⇒ Object

like #cas, but will yield to the block whether or not the value already exists.

Returns:

  • false if the value was changed by someone else.

  • true if the value was successfully updated.



171
172
173
 
# File 'lib/dalli/client.rb', line 171

def cas!(key, ttl = nil, req_options = nil, &block)
  cas_core(key, true, ttl, req_options, &block)
end

#close ⇒ Object Also known as: reset

Close our connection to each server. If you perform another operation after this, the connections will be re-established.



351
352
353
354
 
# File 'lib/dalli/client.rb', line 351

def close
  @ring&.close
  @ring = nil
end

#decr(key, amt = 1, ttl = nil, default = nil) ⇒ Object

Decr subtracts the given amount from the counter on the memcached server. Amt must be a positive integer value.

memcached counters are unsigned and cannot hold negative values. Calling decr on a counter which is 0 will just return 0.

If default is nil, the counter must already exist or the operation will fail and will return nil. Otherwise this method will return the new value for the counter.

Note that the ttl will only apply if the counter does not already exist. To decrease an existing counter and update its TTL, use #cas.

If the value already exists, it must have been set with raw: true



294
295
296
297
298
 
# File 'lib/dalli/client.rb', line 294

def decr(key, amt = 1, ttl = nil, default = nil)
  check_positive!(amt)

  perform(:decr, key, amt.to_i, ttl_or_default(ttl), default)
end

#delete(key) ⇒ Object 



241
242
243
 
# File 'lib/dalli/client.rb', line 241

def delete(key)
  delete_cas(key, 0)
end

#delete_cas(key, cas = 0) ⇒ Object

Delete a key/value pair, verifying existing CAS. Returns true if succeeded, and falsy otherwise.



237
238
239
 
# File 'lib/dalli/client.rb', line 237

def delete_cas(key, cas = 0)
  perform(:delete, key, cas)
end

#fetch(key, ttl = nil, req_options = nil) ⇒ Object

Fetch the value associated with the key. If a value is found, then it is returned.

If a value is not found and no block is given, then nil is returned.

If a value is not found (or if the found value is nil and :cache_nils is false) and a block is given, the block will be invoked and its return value written to the cache and returned.



139
140
141
142
143
144
145
146
147
 
# File 'lib/dalli/client.rb', line 139

def fetch(key, ttl = nil, req_options = nil)
  req_options = req_options.nil? ? CACHE_NILS : req_options.merge(CACHE_NILS) if cache_nils
  val = get(key, req_options)
  return val unless block_given? && not_found?(val)

  new_val = yield
  add(key, new_val, ttl_or_default(ttl), req_options)
  new_val
end

#flush(delay = 0) ⇒ Object Also known as: flush_all

Flush the memcached server, at ‘delay’ seconds in the future. Delay defaults to zero seconds, which means an immediate flush.



304
305
306
 
# File 'lib/dalli/client.rb', line 304

def flush(delay = 0)
  ring.servers.map { |s| s.request(:flush, delay) }
end

#gat(key, ttl = nil) ⇒ Object

Gat (get and touch) fetch an item and simultaneously update its expiration time.

If a value is not found, then nil is returned.



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

def gat(key, ttl = nil)
  perform(:gat, key, ttl_or_default(ttl))
end

#get(key, req_options = nil) ⇒ Object

Get the value associated with the key. If a value is not found, then nil is returned.



63
64
65
 
# File 'lib/dalli/client.rb', line 63

def get(key, req_options = nil)
  perform(:get, key, req_options)
end

#get_cas(key) {|value, cas| ... } ⇒ Object

Get the value and CAS ID associated with the key. If a block is provided, value and CAS will be passed to the block.

Yields:



87
88
89
90
91
92
93
94
 
# File 'lib/dalli/client.rb', line 87

def get_cas(key)
  (value, cas) = perform(:cas, key)
  #  TODO: This is odd.  Confirm this is working as expected.
  value = nil if !value || value == 'Not found'
  return [value, cas] unless block_given?

  yield value, cas
end

#get_multi(*keys) ⇒ Object

Fetch multiple keys efficiently. If a block is given, yields key/value pairs one at a time. Otherwise returns a hash of { ‘key’ => ‘value’, ‘key2’ => ‘value1’ }



100
101
102
103
104
105
106
107
108
109
110
111
112
113
 
# File 'lib/dalli/client.rb', line 100

def get_multi(*keys)
  keys.flatten!
  keys.compact!

  return {} if keys.empty?

  if block_given?
    pipelined_getter.process(keys) { |k, data| yield k, data.first }
  else
    {}.tap do |hash|
      pipelined_getter.process(keys) { |k, data| hash[k] = data.first }
    end
  end
end

#get_multi_cas(*keys) ⇒ Object

Fetch multiple keys efficiently, including available metadata such as CAS. If a block is given, yields key/data pairs one a time. Data is an array:

value, cas_id

If no block is given, returns a hash of

{ 'key' => [value, cas_id] }



121
122
123
124
125
126
127
128
129
 
# File 'lib/dalli/client.rb', line 121

def get_multi_cas(*keys)
  if block_given?
    pipelined_getter.process(keys) { |*args| yield(*args) }
  else
    {}.tap do |hash|
      pipelined_getter.process(keys) { |k, data| hash[k] = data }
    end
  end
end

#incr(key, amt = 1, ttl = nil, default = nil) ⇒ Object

Incr adds the given amount to the counter on the memcached server. Amt must be a positive integer value.

If default is nil, the counter must already exist or the operation will fail and will return nil. Otherwise this method will return the new value for the counter.

Note that the ttl will only apply if the counter does not already exist. To increase an existing counter and update its TTL, use #cas.

If the value already exists, it must have been set with raw: true



272
273
274
275
276
 
# File 'lib/dalli/client.rb', line 272

def incr(key, amt = 1, ttl = nil, default = nil)
  check_positive!(amt)

  perform(:incr, key, amt.to_i, ttl_or_default(ttl), default)
end

#not_found?(val) ⇒ Boolean

Returns:

  • (Boolean) 


359
360
361
 
# File 'lib/dalli/client.rb', line 359

def not_found?(val)
  cache_nils ? val == ::Dalli::NOT_FOUND : val.nil?
end

#prepend(key, value) ⇒ Object

Prepend value to the value already stored on the server for ‘key’. Prepending only works for values stored with :raw => true.



255
256
257
 
# File 'lib/dalli/client.rb', line 255

def prepend(key, value)
  perform(:prepend, key, value.to_s)
end

#quiet ⇒ Object Also known as: multi

Turn on quiet aka noreply support for a number of memcached operations.

All relevant operations within this block will be effectively pipelined as Dalli will use ‘quiet’ versions. The invoked methods will all return nil, rather than their usual response. Method latency will be substantially lower, as the caller will not be blocking on responses.

Currently supports storage (set, add, replace, append, prepend), arithmetic (incr, decr), flush and delete operations. Use of unsupported operations inside a block will raise an error.

Any error replies will be discarded at the end of the block, and Dalli client methods invoked inside the block will not have return values



192
193
194
195
196
197
198
199
 
# File 'lib/dalli/client.rb', line 192

def quiet
  old = Thread.current[::Dalli::QUIET]
  Thread.current[::Dalli::QUIET] = true
  yield
ensure
  @ring&.pipeline_consume_and_ignore_responses
  Thread.current[::Dalli::QUIET] = old
end

#replace(key, value, ttl = nil, req_options = nil) ⇒ Object

Conditionally add a key/value pair, only if the key already exists on the server. Returns truthy if the operation succeeded.



223
224
225
 
# File 'lib/dalli/client.rb', line 223

def replace(key, value, ttl = nil, req_options = nil)
  replace_cas(key, value, 0, ttl, req_options)
end

#replace_cas(key, value, cas, ttl = nil, req_options = nil) ⇒ Object

Conditionally add a key/value pair, verifying existing CAS, only if the key already exists on the server. Returns the new CAS value if the operation succeeded, or falsy otherwise.



231
232
233
 
# File 'lib/dalli/client.rb', line 231

def replace_cas(key, value, cas, ttl = nil, req_options = nil)
  perform(:replace, key, value, ttl_or_default(ttl), cas, req_options)
end

#reset_stats ⇒ Object

Reset stats for each server.



326
327
328
329
330
 
# File 'lib/dalli/client.rb', line 326

def reset_stats
  ring.servers.map do |server|
    server.alive? ? server.request(:reset_stats) : nil
  end
end

#set(key, value, ttl = nil, req_options = nil) ⇒ Object 



202
203
204
 
# File 'lib/dalli/client.rb', line 202

def set(key, value, ttl = nil, req_options = nil)
  set_cas(key, value, 0, ttl, req_options)
end

#set_cas(key, value, cas, ttl = nil, req_options = nil) ⇒ Object

Set the key-value pair, verifying existing CAS. Returns the resulting CAS value if succeeded, and falsy otherwise.



209
210
211
 
# File 'lib/dalli/client.rb', line 209

def set_cas(key, value, cas, ttl = nil, req_options = nil)
  perform(:set, key, value, ttl_or_default(ttl), cas, req_options)
end

#stats(type = nil) ⇒ Object

Collect the stats for each server. You can optionally pass a type including :items, :slabs or :settings to get specific stats Returns a hash like { ‘hostname:port’ => { ‘stat1’ => ‘value1’, … }, ‘hostname2:port’ => { … } }



315
316
317
318
319
320
321
322
 
# File 'lib/dalli/client.rb', line 315

def stats(type = nil)
  type = nil unless ALLOWED_STAT_KEYS.include? type
  values = {}
  ring.servers.each do |server|
    values[server.name.to_s] = server.alive? ? server.request(:stats, type.to_s) : nil
  end
  values
end

#touch(key, ttl = nil) ⇒ Object

Touch updates expiration time for a given key.

Returns true if key exists, otherwise nil.



79
80
81
82
 
# File 'lib/dalli/client.rb', line 79

def touch(key, ttl = nil)
  resp = perform(:touch, key, ttl_or_default(ttl))
  resp.nil? ? nil : true
end

#version ⇒ Object

Version of the memcache servers.



334
335
336
337
338
339
340
 
# File 'lib/dalli/client.rb', line 334

def version
  values = {}
  ring.servers.each do |server|
    values[server.name.to_s] = server.alive? ? server.request(:version) : nil
  end
  values
end

#with {|_self| ... } ⇒ Object

Stub method so a bare Dalli client can pretend to be a connection pool.

Yields:

  • (_self)

Yield Parameters:

  • _self (Dalli::Client) —

    the object that the method was called on



368
369
370
 
# File 'lib/dalli/client.rb', line 368

def with
  yield self
end