CL-MEMCACHED is a library to interface with the memcached object caching system.
What is Memcached?? According to the home page :
memcached is a high-performance, distributed memory object caching system, generic in nature, but intended for use in speeding up dynamic web applications by alleviating database load.
Danga Interactive developed memcached to enhance the speed of LiveJournal.com, a site which was already doing 20 million+ dynamic page views per day for 1 million users with a bunch of webservers and a bunch of database servers. memcached dropped the database load to almost nothing, yielding faster page load times for users, better resource utilization, and faster access to the databases on a memcache miss.
CL-MEMCACHED implements most of the memcached protocol. The code has been tested on Allegro CL and does not work on other Lisp's right now. See file compat.lisp to help.
We have used memcached (1.1.2) in production for over 20 months and have found it to give excellent performance and good stability. The CL-MEMCACHED has evolved over this period of time from a hack to it's current state. Our memcached servers have been up for over 60 days at a time having served over a terabyte of data to the network in this period.
Here are some sample performance statistics of CL-MEMCACHED and other memcached clients :
| client | lang implementation | 10,000 writes 1K data (in msec) | 10,000 reads 1K data (in msec) | 10,000 writes 10K data (in msec) | 10,000 reads 10K data (in msec) |
|---|---|---|---|---|---|
| cl-memcached | Allegro 8.0 (AMD64) | 950 | 830 | 2,130 | 1,330 |
| memcached-client-1.2.0 | ruby 1.8.5 | 727 | 874 | 1,129 | 1,296 |
| python-memcached-1.36 | python 2.5.1 | 892 | 951 | 1,092 | 1,259 |
| php-memcached-2.1.2 | php 4.3.9 | 507 | 513 | 400,000 | 660 |
The code comes with a BSD-style license so you can basically do with it whatever you want.
Download shortcut: cl-memcached-latest.tar.gz.
quick start
CL-USER> (asdf:oos 'asdf:load-op :cl-memcached)
CL-USER> (setf *my-cache* (cl-memcached:mc-make-memcache-instance :ip "127.0.0.1" :name "My test cache"))
#<CL-MEMCACHED:MEMCACHE My test cache on 127.0.0.1:11211 SIZE:64Mb>
CL-USER> (cl-memcached:mc-store "test-key" "This is Test-DATA" :memcache *my-cache* :use-pool t)
"STORED"
CL-USER> (cl-memcached:mc-get+ "test-key" :memcache *my-cache* :use-pool t)
"This is Test-DATA"
CL-USER> (cl-memcached:mc-get '("test-key") :memcache *my-cache* :use-pool t)
(("test-key"
#(84 104 105 115 32 105 115 32 84 101 115 116 45 68 65 84 65)))
CL-USER> (cl-memcached:mc-get '("test-key") :memcache *my-cache* :use-pool t :is-string t)
(("test-key" "This is Test-DATA"))
CL-USER> (cl-memcached:mc-store "test-key-2" "This is Test-DATA Again" :memcache *my-cache* :use-pool t)
"STORED"
CL-USER> (cl-memcached:mc-get '("test-key" "test-key-2") :memcache *my-cache* :use-pool t :is-string t)
(("test-key" "This is Test-DATA")
("test-key-2" "This is Test-DATA Again"))
[Special variable]
*memcache*
We can set the current memcache instance to this if there is only one in use.
[Special variable]
*use-pool*
This controls if we use the connection pool by default. One can set it at each call level, but it is also possible to set this global policy. Default value for the USE-POOL is nil, which means a new connection is make every request.
[Special variable]
*pool-get-trys?*
This controls the policy for the fetching connectors from the pool. There are two approaches : a) where we throw an error if pool is empty b) where we sleep an try again to see if one is available. The default value is nil which is the a) approach.
[Function]
mc-store key data &key memcache command timeout use-pool => result
Stores data in the memcached server.key - key by which the data is stored. this is of type SIMPLE-STRING data - data to be stored into the cache. data is a sequence of type (UNSIGNED-BYTE 8) length - size of data memcache - The instance of class memcache which represnts the memcached we want to use. command - The storage command we want to use. There are 3 available : set, add & replace. timeout - The time in seconds when this data expires. 0 is never expire.
[Function]
mc-get keys-list &key memcache use-pool is-string => result
Retrive value for key from memcached server.keys-list - is a list of the keys, seperated by whitespace, by which data is stored in memcached memcache - The instance of class memcache which represnts the memcached we want to use. Returns a list of lists where each list has two elements key and value key - is of type SIMPLE-STRING value is of type (UNSIGNED-BYTE 8)
[Function]
mc-get+ key-or-list-of-keys &key memcache use-pool => result
To be used for non-binary data only. If one key is given returns the response in string format
[Function]
mc-decr key &key memcache value use-pool => result
Implements the DECR command. Decrements the value of a key. Please read memcached documentation for more information
[Function]
mc-del key &key memcache time use-pool => result
Deletes a particular 'key' and it's associated data from the memcached server
[Function]
mc-incr key &key memcache value use-pool => result
Implements the INCR command. Increments the value of a key. Please read memcached documentation for more information
[Function]
mc-make-memcache-instance &key ip port name pool-size => result
Creates an instance of class MEMCACHE which represents a memcached server
[Function]
mc-pool-init &key memcache => result
Cleans up the pool for this particular instance of memcache & reinits it with POOL-SIZE number of objects required by this pool
[Function]
mc-server-check &key memcache => result
Performs some basic tests on the Memcache instance and outputs a status string
[Function]
mc-stats &key memcache use-pool => result
Returns a struct of type memcache-stats which contains internal statistics from the memcached server instance. Please refer to documentation of memcache-stats for detailed information about each slot.
[Structure]
memcache-stats
The structure which holds the statistics from the memcached server. The fields are :field-name accessor-function documentation ---------- ----------------- ------------- pid mc-stats-pid Process id of this server process uptime mc-stats-uptime Number of seconds this server has been running time mc-stats-time current UNIX time according to the server version mc-stats-version Version string of this server rusage-user mc-stats-rusage-user Accumulated user time for this process rusage-system mc-stats-rusage-system Accumulated system time for this process curr-items mc-stats-curr-items Current number of items stored by the server total-items mc-stats-total-items Total number of items stored by this server ever since it started bytes mc-stats-bytes Current number of bytes used by this server to store items curr-connections mc-stats-curr-connections Number of open connections total-connections mc-stats-total-connections Total number of connections opened since the server started running connection-structures mc-stats-connection-structures Number of connection structures allocated by the server cmd-get mc-stats-cmd-get Cumulative number of retrieval requests cmd-set mc-stats-cmd-set Cumulative number of storage requests get-hits mc-stats-get-hits Number of keys that have been requested and found present get-misses mc-stats-get-misses Number of items that have been requested and not found evictions mc-stats-evictions Number of items removed from cache because they passed their expiration time bytes-read mc-stats-bytes-read Total number of bytes read by this server from network bytes-written mc-stats-bytes-written Total number of bytes sent by this server to network limit-maxbytes mc-stats-limit-maxbytes Number of bytes this server is allowed to use for storage.
[Standard class]
memcache
This class represents an instance of the Memcached server(defclass memcache () ((name :initarg :name :reader name :type simple-string :documentation "Name of this Memcache instance") (ip :initarg :ip :initform "127.0.0.1" :accessor ip :type simple-string :documentation "The IP address of the Memcached server this instance represents") (port :initarg :port :initform 11211 :accessor port :type fixnum :documentation "The port on which the Memcached server this instance represents runs") (memcached-server-storage-size :initform 0 :reader memcached-server-storage-size :type fixnum :documentation "Memory allocated to the Memcached Server") (pool-size :initarg :pool-size :initform 2 :reader pool-size) (pool :reader pool)) (:documentation "This class represents an instance of the Memcached server"))
Abhijit 'quasi' Rao
Chaitanya Gupta
Thanks to Mr. Hrush Bhatt of Cleartrip for allowing us to make this library available under a BSD licence.
This documentation was prepared with the help of DOCUMENTATION-TEMPLATE.