class Dalli::Client

Constants

CACHE_NILS

Public Class Methods

new(servers=nil, options={}) click to toggle source

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'],
                :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 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 - defaults to false, if true Dalli will compress values larger than 1024 bytes before sending them to memcached.

  • :serializer - defaults to Marshal

  • :compressor - defaults to zlib

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

# File lib/dalli/client.rb, line 32
def initialize(servers=nil, options={})
  @servers = normalize_servers(servers || ENV["MEMCACHE_SERVERS"] || '127.0.0.1:11211')
  @options = normalize_options(options)
  @ring = nil
end

Public Instance Methods

add(key, value, ttl=nil, options=nil) click to toggle source

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

# File lib/dalli/client.rb, line 132
def add(key, value, ttl=nil, options=nil)
  perform(:add, key, value, ttl_or_default(ttl), options)
end
alive!() click to toggle source

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

# File lib/dalli/client.rb, line 235
def alive!
  ring.server_for_key("")
end
append(key, value) click to toggle source

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

# File lib/dalli/client.rb, line 150
def append(key, value)
  perform(:append, key, value.to_s)
end
cas(key, ttl=nil, options=nil, &block) click to toggle source

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.

# File lib/dalli/client.rb, line 110
def cas(key, ttl=nil, options=nil, &block)
  cas_core(key, false, ttl, options, &block)
end
cas!(key, ttl=nil, options=nil, &block) click to toggle source

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.

# File lib/dalli/client.rb, line 121
def cas!(key, ttl=nil, options=nil, &block)
  cas_core(key, true, ttl, options, &block)
end
close() click to toggle source

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

# File lib/dalli/client.rb, line 252
def close
  if @ring
    @ring.servers.each { |s| s.close }
    @ring = nil
  end
end
Also aliased as: reset
decr(key, amt=1, ttl=nil, default=nil) click to toggle source

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.

# File lib/dalli/client.rb, line 198
def decr(key, amt=1, ttl=nil, default=nil)
  raise ArgumentError, "Positive values only: #{amt}" if amt < 0
  perform(:decr, key, amt.to_i, ttl_or_default(ttl), default)
end
delete(key) click to toggle source
# File lib/dalli/client.rb, line 143
def delete(key)
  perform(:delete, key, 0)
end
delete_cas(key, cas=0) click to toggle source

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

# File lib/dalli/cas/client.rb, line 53
def delete_cas(key, cas=0)
  perform(:delete, key, cas)
end
fetch(key, ttl=nil, options=nil) { || ... } click to toggle source

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.

# File lib/dalli/client.rb, line 86
def fetch(key, ttl=nil, options=nil)
  options = options.nil? ? CACHE_NILS : options.merge(CACHE_NILS) if @options[:cache_nils]
  val = get(key, options)
  not_found = @options[:cache_nils] ?
    val == Dalli::Server::NOT_FOUND :
    val.nil?
  if not_found && block_given?
    val = yield
    add(key, val, ttl_or_default(ttl), options)
  end
  val
end
flush(delay=0) click to toggle source
# File lib/dalli/client.rb, line 161
def flush(delay=0)
  time = -delay
  ring.servers.map { |s| s.request(:flush, time += delay) }
end
Also aliased as: flush_all
flush_all(delay=0) click to toggle source
Alias for: flush
get(key, options=nil) click to toggle source

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

# File lib/dalli/client.rb, line 57
def get(key, options=nil)
  perform(:get, key, options)
end
get_cas(key) { |value, cas| ... } click to toggle source

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

# File lib/dalli/cas/client.rb, line 8
def get_cas(key)
  (value, cas) = perform(:cas, key)
  value = (!value || value == 'Not found') ? nil : value
  if block_given?
    yield value, cas
  else
    [value, cas]
  end
end
get_multi(*keys) { |k, first| ... } click to toggle source

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’ }

# File lib/dalli/client.rb, line 65
def get_multi(*keys)
  return {} if keys.flatten.compact.empty?
  if block_given?
    get_multi_yielder(keys) {|k, data| yield k, data.first}
  else
    Hash.new.tap do |hash|
      get_multi_yielder(keys) {|k, data| hash[k] = data.first}
    end
  end
end
get_multi_cas(*keys) { |*args| ... } click to toggle source

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] }
# File lib/dalli/cas/client.rb, line 24
def get_multi_cas(*keys)
  if block_given?
    get_multi_yielder(keys) {|*args| yield(*args)}
  else
    Hash.new.tap do |hash|
      get_multi_yielder(keys) {|k, data| hash[k] = data}
    end
  end
end
incr(key, amt=1, ttl=nil, default=nil) click to toggle source

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.

# File lib/dalli/client.rb, line 179
def incr(key, amt=1, ttl=nil, default=nil)
  raise ArgumentError, "Positive values only: #{amt}" if amt < 0
  perform(:incr, key, amt.to_i, ttl_or_default(ttl), default)
end
multi() { || ... } click to toggle source

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

# File lib/dalli/client.rb, line 47
def multi
  old, Thread.current[:dalli_multi] = Thread.current[:dalli_multi], true
  yield
ensure
  Thread.current[:dalli_multi] = old
end
prepend(key, value) click to toggle source

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

# File lib/dalli/client.rb, line 157
def prepend(key, value)
  perform(:prepend, key, value.to_s)
end
replace(key, value, ttl=nil, options=nil) click to toggle source

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

# File lib/dalli/client.rb, line 139
def replace(key, value, ttl=nil, options=nil)
  perform(:replace, key, value, ttl_or_default(ttl), 0, options)
end
replace_cas(key, value, cas, ttl=nil, options=nil) click to toggle source

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.

# File lib/dalli/cas/client.rb, line 46
def replace_cas(key, value, cas, ttl=nil, options=nil)
  ttl ||= @options[:expires_in].to_i
  perform(:replace, key, value, ttl, cas, options)
end
reset() click to toggle source
Alias for: close
reset_stats() click to toggle source

Reset stats for each server.

# File lib/dalli/client.rb, line 227
def reset_stats
  ring.servers.map do |server|
    server.alive? ? server.request(:reset_stats) : nil
  end
end
set(key, value, ttl=nil, options=nil) click to toggle source
# File lib/dalli/client.rb, line 125
def set(key, value, ttl=nil, options=nil)
  perform(:set, key, value, ttl_or_default(ttl), 0, options)
end
set_cas(key, value, cas, ttl=nil, options=nil) click to toggle source

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

# File lib/dalli/cas/client.rb, line 37
def set_cas(key, value, cas, ttl=nil, options=nil)
  ttl ||= @options[:expires_in].to_i
  perform(:set, key, value, ttl, cas, options)
end
stats(type=nil) click to toggle source

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’ => { … } }

# File lib/dalli/client.rb, line 216
def stats(type=nil)
  type = nil if ![nil, :items,:slabs,:settings].include? type
  values = {}
  ring.servers.each do |server|
    values["#{server.name}"] = server.alive? ? server.request(:stats,type.to_s) : nil
  end
  values
end
touch(key, ttl=nil) click to toggle source

Touch updates expiration time for a given key.

Returns true if key exists, otherwise nil.

# File lib/dalli/client.rb, line 207
def touch(key, ttl=nil)
  resp = perform(:touch, key, ttl_or_default(ttl))
  resp.nil? ? nil : true
end
version() click to toggle source

Version of the memcache servers.

# File lib/dalli/client.rb, line 241
def version
  values = {}
  ring.servers.each do |server|
    values["#{server.name}"] = server.alive? ? server.request(:version) : nil
  end
  values
end
with() { |self| ... } click to toggle source

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

# File lib/dalli/client.rb, line 261
def with
  yield self
end