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
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
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 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
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
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 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
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
# File lib/dalli/client.rb, line 143 def delete(key) perform(:delete, key, 0) end
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 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
# File lib/dalli/client.rb, line 161 def flush(delay=0) time = -delay ring.servers.map { |s| s.request(:flush, time += delay) } end
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 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
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
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:
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 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
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 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
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
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 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
# 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 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
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 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 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
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