Class: Dalli::Client

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

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'], 
                :threadsafe => true, :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 default to ‘localhost:11211’. Note that the MEMCACHE_SERVERS environment variable will override the servers parameter for use in managed environments like Heroku.

Options:

  • :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

  • :compression - defaults to false, if true Dalli will compress values larger than 100 bytes before

    sending them to memcached.



24
25
26
27
 
# File 'lib/dalli/client.rb', line 24

def initialize(servers=nil, options={})
  @servers = env_servers || servers || 'localhost:11211'
  @options = { :expires_in => 0 }.merge(options)
end

Instance Method Details

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

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



109
110
111
112
 
# File 'lib/dalli/client.rb', line 109

def add(key, value, ttl=nil, options=nil)
  ttl ||= @options[:expires_in]
  perform(:add, key, value, ttl, 0, options)
end

#append(key, value) ⇒ Object 



126
127
128
 
# File 'lib/dalli/client.rb', line 126

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

#cas(key, ttl = nil, 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.



91
92
93
94
95
96
97
98
99
 
# File 'lib/dalli/client.rb', line 91

def cas(key, ttl=nil, options=nil, &block)
  ttl ||= @options[:expires_in]
  (value, cas) = perform(:cas, key)
  value = (!value || value == 'Not found') ? nil : value
  if value
    newvalue = block.call(value)
    perform(:add, key, newvalue, ttl, cas, options)
  end
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.



190
191
192
193
194
195
 
# File 'lib/dalli/client.rb', line 190

def close
  if @ring
    @ring.servers.map { |s| s.close }
    @ring = nil
  end
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 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.

Raises:

  • (ArgumentError) 


170
171
172
173
174
 
# File 'lib/dalli/client.rb', line 170

def decr(key, amt=1, ttl=nil, default=nil)
  raise ArgumentError, "Positive values only: #{amt}" if amt < 0
  ttl ||= @options[:expires_in]
  perform(:decr, key, amt, ttl, default)
end

#delete(key) ⇒ Object 



122
123
124
 
# File 'lib/dalli/client.rb', line 122

def delete(key)
  perform(:delete, key)
end

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



70
71
72
73
74
75
76
77
78
 
# File 'lib/dalli/client.rb', line 70

def fetch(key, ttl=nil, options=nil)
  ttl ||= @options[:expires_in]
  val = get(key, options)
  if val.nil? && block_given?
    val = yield
    add(key, val, ttl, options)
  end
  val
end

#flush(delay = 0) ⇒ Object 



134
135
136
137
 
# File 'lib/dalli/client.rb', line 134

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

#flush_all(delay = 0) ⇒ Object

deprecated, please use #flush.



140
141
142
 
# File 'lib/dalli/client.rb', line 140

def flush_all(delay=0)
  flush(delay)
end

#get(key, options = nil) ⇒ Object 



45
46
47
48
 
# File 'lib/dalli/client.rb', line 45

def get(key, options=nil)
  resp = perform(:get, key)
  (!resp || resp == 'Not found') ? nil : resp
end

#get_multi(*keys) ⇒ Object

Fetch multiple keys efficiently. Returns a hash of { ‘key’ => ‘value’, ‘key2’ => ‘value1’ }



53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
 
# File 'lib/dalli/client.rb', line 53

def get_multi(*keys)
  return {} if keys.empty?
  options = nil
  options = keys.pop if keys.last.is_a?(Hash) || keys.last.nil?
  ring.lock do
    keys.flatten.each do |key|
      perform(:getkq, key)
    end

    values = {}
    ring.servers.each do |server|
      values.merge!(server.request(:noop)) if server.alive?
    end
    values
  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 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.

Raises:

  • (ArgumentError) 


154
155
156
157
158
 
# File 'lib/dalli/client.rb', line 154

def incr(key, amt=1, ttl=nil, default=nil)
  raise ArgumentError, "Positive values only: #{amt}" if amt < 0
  ttl ||= @options[:expires_in]
  perform(:incr, key, amt, ttl, default)
end

#multi ⇒ Object

Turn on quiet aka noreply support. All relevant operations within this block with be effectively pipelined as Dalli will use ‘quiet’ operations where possible. Currently supports the set, add, replace and delete operations.



38
39
40
41
42
43
 
# File 'lib/dalli/client.rb', line 38

def multi
  old, Thread.current[:dalli_multi] = Thread.current[:dalli_multi], true
  yield
ensure
  Thread.current[:dalli_multi] = old
end

#prepend(key, value) ⇒ Object 



130
131
132
 
# File 'lib/dalli/client.rb', line 130

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

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

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



117
118
119
120
 
# File 'lib/dalli/client.rb', line 117

def replace(key, value, ttl=nil, options=nil)
  ttl ||= @options[:expires_in]
  perform(:replace, key, value, ttl, options)
end

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



101
102
103
104
 
# File 'lib/dalli/client.rb', line 101

def set(key, value, ttl=nil, options=nil)
  ttl ||= @options[:expires_in]
  perform(:set, key, value, ttl, options)
end

#stats ⇒ Object

Collect the stats for each server. Returns a hash like { ‘hostname:port’ => { ‘stat1’ => ‘value1’, … }, ‘hostname2:port’ => { … } }



179
180
181
182
183
184
185
 
# File 'lib/dalli/client.rb', line 179

def stats
  values = {}
  ring.servers.each do |server|
    values["#{server.hostname}:#{server.port}"] = server.alive? ? server.request(:stats) : nil
  end
  values
end