class ActiveSupport::Cache::MemCacheStore
Memcached Cache Store
A cache store implementation which stores data in Memcached: memcached.org
This is currently the most popular cache store for production websites.
Special features:
-
Clustering and load balancing. One can specify multiple memcached servers, and
MemCacheStore
will load balance between all available servers. If a server goes down, thenMemCacheStore
will ignore it until it comes back up.
MemCacheStore
implements the Strategy::LocalCache
strategy which implements an in-memory cache inside of a block.
Inherits From
Constants
These options represent behavior overridden by this implementation and should not be allowed to get down to the Dalli client
UNIVERSAL_OPTIONS
Public class methods
Creates a new MemCacheStore
object, with the given memcached server addresses. Each address is either a host name, or a host-with-port string in the form of “host_name:port”. For example:
ActiveSupport::Cache::MemCacheStore.new("localhost", "server-downstairs.localnetwork:8229")
If no addresses are provided, but ENV['MEMCACHE_SERVERS']
is defined, it will be used instead. Otherwise, MemCacheStore
will connect to localhost:11211 (the default memcached port).
Source code GitHub
# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 77
def initialize(*addresses)
addresses = addresses.flatten
options = addresses.extract_options!
if options.key?(:cache_nils)
options[:skip_nil] = !options.delete(:cache_nils)
end
super(options)
unless [String, Dalli::Client, NilClass].include?(addresses.first.class)
raise ArgumentError, "First argument must be an empty array, address, or array of addresses."
end
@mem_cache_options = options.dup
# The value "compress: false" prevents duplicate compression within Dalli.
@mem_cache_options[:compress] = false
(OVERRIDDEN_OPTIONS - %i(compress)).each { |name| @mem_cache_options.delete(name) }
@data = self.class.build_mem_cache(*(addresses + [@mem_cache_options]))
end
Advertise cache versioning support.
Source code GitHub
# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 38
def self.supports_cache_versioning?
true
end
Public instance methods
Clear the entire cache on all memcached servers. This method should be used with care when shared cache is being used.
Source code GitHub
# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 171
def clear(options = nil)
rescue_error_with(nil) { @data.with { |c| c.flush_all } }
end
Decrement a cached integer value using the memcached decr atomic operator. Returns the updated value.
If the key is unset or has expired, it will be set to 0. Memcached does not support negative counters.
cache.decrement("foo") # => 0
To set a specific value, call write
passing raw: true
:
cache.write("baz", 5, raw: true)
cache.decrement("baz") # => 4
Decrementing a non-numeric value, or a value written without raw: true
, will fail and return nil
.
Source code GitHub
# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 158
def decrement(name, amount = 1, options = nil)
options = merged_options(options)
key = normalize_key(name, options)
instrument(:decrement, key, amount: amount) do
rescue_error_with nil do
@data.with { |c| c.decr(key, amount, options[:expires_in], 0) }
end
end
end
Increment a cached integer value using the memcached incr atomic operator. Returns the updated value.
If the key is unset or has expired, it will be set to amount
:
cache.increment("foo") # => 1
cache.increment("bar", 100) # => 100
To set a specific value, call write
passing raw: true
:
cache.write("baz", 5, raw: true)
cache.increment("baz") # => 6
Incrementing a non-numeric value, or a value written without raw: true
, will fail and return nil
.
Source code GitHub
# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 132
def increment(name, amount = 1, options = nil)
options = merged_options(options)
key = normalize_key(name, options)
instrument(:increment, key, amount: amount) do
rescue_error_with nil do
@data.with { |c| c.incr(key, amount, options[:expires_in], amount) }
end
end
end
Source code GitHub
# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 96
def inspect
instance = @data || @mem_cache_options
"#<#{self.class} options=#{options.inspect} mem_cache=#{instance.inspect}>"
end
Get the statistics from the memcached servers.
Source code GitHub
# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 176
def stats
@data.with { |c| c.stats }
end
Behaves the same as ActiveSupport::Cache::Store#write
, but supports additional options specific to memcached.
Additional Options
-
raw: true
- Sends the value directly to the server as raw bytes. The value must be a string or number. You can use memcached direct operations likeincrement
anddecrement
only on raw values. -
unless_exist: true
- Prevents overwriting an existing cache entry.