boourns-memcached

memcached

An interface to the libmemcached C client.

== License

Copyright 2009-2011 Cloudburst, LLC. Licensed under the AFL 3. See the included LICENSE file. Portions copyright 2007-2009 TangentOrg, Brian Aker, licensed under the BSD license, and used with permission.

== Features

• clean API
• robust access to all memcached features
• SASL support for the binary protocol
• multiple hashing modes, including consistent hashing
• ludicrous speed, including optional pipelined IO with no_reply

The memcached library wraps the pure-C libmemcached client via SWIG.

== Installation

You need Ruby 1.8.7 or Ruby 1.9.2. Other versions may work, but are not guaranteed. You also need the libsasl2-dev and gettext libraries, which should be provided through your system's package manager.

Install the gem: sudo gem install memcached --no-rdoc --no-ri

== Usage

Start a local networked memcached server: $ memcached -p 11211 &

Now, in Ruby, require the library and instantiate a Memcached object at a global level:

require 'memcached' $cache = Memcached.new("localhost:11211")

Now you can set things and get things:

value = 'hello' $cache.set 'test', value $cache.get 'test' #=> "hello"

You can set with an expiration timeout:

value = 'hello' $cache.set 'test', value, 1 sleep(2) $cache.get 'test' #=> raises Memcached::NotFound

You can get multiple values at once:

value = 'hello' $cache.set 'test', value $cache.set 'test2', value $cache.get ['test', 'test2', 'missing'] #=> {"test" => "hello", "test2" => "hello"}

You can set a counter and increment it. Note that you must initialize it with an integer, encoded as an unmarshalled ASCII string:

start = 1 $cache.set 'counter', start.to_s, 0, false $cache.increment 'counter' #=> 2 $cache.increment 'counter' #=> 3 $cache.get('counter', false).to_i #=> 3

You can get some server stats:

$cache.stats #=> {..., :bytes_written=>[62], :version=>["1.2.4"] ...}

Note that the API is not the same as that of Ruby-MemCache or memcache-client. In particular, nil is a valid record value. Memcached#get does not return nil on failure, rather it raises Memcached::NotFound. This is consistent with the behavior of memcached itself. For example:

$cache.set 'test', nil $cache.get 'test' #=> nil $cache.delete 'test' $cache.get 'test' #=> raises Memcached::NotFound

== Rails

config/environment.rb

require "memcached/rails" config.cache_store = Memcached::Rails.new(:servers => ['127.0.0.1'])

== Pipelining

Pipelining updates is extremely effective in memcached, leading to more than 25x write throughput than the default settings. Use the following options to enable it:

:no_block => true, :buffer_requests => true, :noreply => true, :binary_protocol => false

Currently #append, #prepend, #set, and #delete are pipelined. Note that when you perform a read, all pending writes are flushed to the servers.

== Threading

memcached is threadsafe, but each thread requires its own Memcached instance. Create a global Memcached, and then call Memcached#clone each time you spawn a thread.

thread = Thread.new do cache = $cache.clone # Perform operations on cache, not $cache cache.set 'example', 1 cache.get 'example' end

Join the thread so that exceptions don't get lost

thread.join

== Legacy applications

There is a compatibility wrapper for legacy applications called Memcached::Rails.

== Benchmarks

memcached, correctly configured, is at least twice as fast as memcache-client and dalli. See BENCHMARKS[link:files/BENCHMARKS.html] for details.

== Reporting problems

The support forum is here[http://github.com/evan/memcached/issues].

Patches and contributions are very welcome. Please note that contributors are required to assign copyright for their additions to Cloudburst, LLC.

== Further resources

• {Memcached wiki}[http://www.socialtext.net/memcached/index.cgi]
• {Libmemcached homepage}[http://tangent.org/552/libmemcached.html]