在Windows中安裝Memcached

Memcached是一個高併發的內存鍵值對緩存系統，它的主要做用是將數據庫查詢結果，內容，以及其它一些耗時的計算結果緩存到系統內存中，從而加速Web應用程序的響應速度。

Memcached最開始是做爲Linux應用程序被安裝在Linux服務器上來使用的，不過自從開源以後，它又被從新編譯以適用於Windows環境。Jellycan和Northscale兩個站點都提供了Windows的二進制可執行文件下載，下面是下載的地址：

http://code.jellycan.com/files/memcached-1.2.5-win32-bin.zip

http://code.jellycan.com/files/memcached-1.2.6-win32-bin.zip

http://downloads.northscale.com/memcached-win32-1.4.4-14.zip

http://downloads.northscale.com/memcached-win64-1.4.4-14.zip

http://downloads.northscale.com/memcached-1.4.5-x86.zip

http://downloads.northscale.com/memcached-1.4.5-amd64.zip

在1.4.5版本以前，memcached能夠被安裝成一個服務，但以後的版本中該功能被移除了。所以memcached的安裝能夠分爲兩類，第一類是1.4.5以前的版本，另外一類是1.4.5以後的版本。

安裝memcached < 1.4.5:

1. 將下載的文件解壓到任意目錄。

2. 1.4.5以前版本的memcached會被安裝成一個服務，以administrator打開控制檯，運行下面的命令：

c:\memcached\memcached.exe -d install

* 注意將路徑c:\memcached\memcached.exe替換成你本地的安裝路徑。

3. 而後使用下面的命令啓動或中止memcached服務：

c:\memcached\memcached.exe -d start
c:\memcached\memcached.exe -d stop

4. 經過註冊表鍵值來修改memcached的配置項。在運行中輸入regedit.exe，而後導航到"HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\memcached"。修改其中的鍵值。例如你想增長memcached所使用的最大內存限制，能夠修改ImagePath的值：

"c:\memcached\memcached.exe" -d runservice -m 512

* 除了參數'-m 512'以外，你還可使用其它的參數。經過「c:\memcached\memcached.exe -h」能夠查看全部能使用的參數。

5. 若是要卸載memcached服務，可使用下面的命令：

c:\memcached\memcached.exe -d uninstall

 安裝memcached >= 1.4.5

1. 將下載的文件解壓到任意目錄。

2. 1.4.5以後版本的memcached不能做爲Windows服務來運行，必須使用Windows計劃任務來運行它。要將memcached配置成當Windows啓動時自動運行，在命令行運行下面的命令：

schtasks /create /sc onstart /tn memcached /tr "'c:\memcached\memcached.exe' -m 512"

* 注意將路徑c:\memcached\memcached.exe替換成你本地的安裝路徑。

** 除了參數'-m 512'以外，你還可使用其它的參數。經過「c:\memcached\memcached.exe -h」能夠查看全部能使用的參數。

3. 經過下面的命令將memcached從Windows計劃任務中移除：

schtasks /delete /tn memcached

在PHP中使用memcached

要在PHP中使用memcached，首先須要安裝memcache擴展包：

1. 查看你本地的PHP擴展包目錄裏是否有php_memcache.dll這個文件，若是沒有，從https://pecl.php.net/package/memcache下載（選擇windows dll文件），而後複製到PHP擴展包目錄裏。

2. 在php.ini中添加下面的代碼以啓用memcache擴展包：

extension=php_memcache.dll

3. 建立下面的php示例代碼進行測試：

<?php

$memcache = new Memcache;
$memcache->connect('localhost', 11211) or die ("Could not connect");

$version = $memcache->getVersion();
echo "Server's version: ".$version."<br/>\n";

$tmp_object = new stdClass;
$tmp_object->str_attr = 'test';
$tmp_object->int_attr = 123;

$memcache->set('key', $tmp_object, false, 10) or die ("Failed to save data at the server");
echo "Store data in the cache (data will expire in 10 seconds)<br/>\n";

$get_result = $memcache->get('key');
echo "Data from the cache:<br/>\n";

var_dump($get_result);

?>

在Python中使用memcached

要在Python中使用memcached，首先須要安裝memcached客戶端：

1. 執行下面的命令進行memcached客戶端的安裝。第一個適用於Python 2.x，第二個適用於Python 3.x。

pip install python-memcached
pip install python3-memcached

2. 建立下面的python示例代碼進行測試：

import memcache
mc = memcache.Client(['127.0.0.1:11211'], debug=0)
mc.set("some_key", "Some value")
value = mc.get("some_key")
mc.set("another_key", 3)
mc.delete("another_key")
mc.set("key", "1")   # note that the key used for incr/decr must be a string.
mc.incr("key")
mc.decr("key")

在Node.js中使用memcached

在Node.js中能夠經過memcached包來使用memcache，Github的地址https://github.com/3rd-Eden/memcached。下面是一段示例代碼：

var Memcached = require( 'memcached' );

// connect to our memcached server on host 10.211.55.5, port 11211
var memcached = new Memcached( "10.211.55.5:11211" );

memcached.set( "hello", 1, 10000, function( err, result ){
    if( err ) console.error( err );
    
    console.dir( result );
    memcached.end(); // as we are 100% certain we are not going to use the connection again, we are going to end it
});

memcached.get( "hello", function( err, result ){
    if( err ) console.error( err );
    
    console.dir( result );
    memcached.end(); // as we are 100% certain we are not going to use the connection again, we are going to end it
});

更詳細的使用方法能夠參考Github上的說明。

在Golang中使用memcached

package main

import (
	"fmt"
	"github.com/bradfitz/gomemcache/memcache"
)
var (
	server = "127.0.0.1:11211"
)
func main() {
	//create a handle
	mc := memcache.New(server)
	if mc == nil {
		fmt.Println("memcache New failed")
	}

	//set key-value
	mc.Set(&memcache.Item{Key: "foo", Value: []byte("my value")})

	//get key's value
	it, _ := mc.Get("foo")
	if string(it.Key) == "foo" {
		fmt.Println("value is ", string(it.Value))
	} else {
		fmt.Println("Get failed")
	}
	///Add a new key-value
	mc.Add(&memcache.Item{Key: "foo", Value: []byte("bluegogo")})
	it, err := mc.Get("foo")
	if err != nil {
		fmt.Println("Add failed")
	} else {
		if string(it.Key) == "foo" {
			fmt.Println("Add value is ", string(it.Value))
		} else {
			fmt.Println("Get failed")
		}
	}
	//replace a key's value
	mc.Replace(&memcache.Item{Key: "foo", Value: []byte("mobike")})
	it, err = mc.Get("foo")
	if err != nil {
		fmt.Println("Replace failed")
	} else {
		if string(it.Key) == "foo" {
			fmt.Println("Replace value is ", string(it.Value))
		} else {
			fmt.Println("Replace failed")
		}
	}
	//delete an exist key
	err = mc.Delete("foo")
	if err != nil {
		fmt.Println("Delete failed:", err.Error())
	}
	//incrby
	err = mc.Set(&memcache.Item{Key: "aaa", Value: []byte("1")})
	if err != nil {
		fmt.Println("Set failed :", err.Error())
	}
	it, err = mc.Get("foo")
	if err != nil {
		fmt.Println("Get failed ", err.Error())
	} else {
		fmt.Println("src value is:", it.Value)
	}
	value, err := mc.Increment("aaa", 7)
	if err != nil {
		fmt.Println("Increment failed")
	} else {
		fmt.Println("after increment the value is :", value)
	}
	//decrby
	value, err = mc.Decrement("aaa", 4)
	if err != nil {
		fmt.Println("Decrement failed", err.Error())
	} else {
		fmt.Println("after decrement the value is ", value)
	}
}

Memcached的數據統計

要查看memcached的數據統計，能夠經過telnet鏈接到memcached：

telnet 127.0.0.1 11211

* ip地址後面的數字爲memcached運行的端口號

** 在Windows 10中telnet組件默認並無添加，可經過Control Panel > Programs and Features > Turn Windows features on or off來添加。

而後使用stats來查看統計信息。下表列出了stats統計結果中各數據項的含義：

Name	Type	Meaning
pid	32u	Process id of this server process
uptime	32u	Number of secs since the server started
time	32u	current UNIX time according to the server
version	string	Version string of this server
pointer_size	32	Default size of pointers on the host OS (generally 32 or 64)
rusage_user	32u.32u	Accumulated user time for this process (seconds:microseconds)
rusage_system	32u.32u	Accumulated system time for this process (seconds:microseconds)
curr_items	32u	Current number of items stored
total_items	32u	Total number of items stored since the server started
bytes	64u	Current number of bytes used to store items
curr_connections	32u	Number of open connections
total_connections	32u	Total number of connections opened since the server started running
connection_structures	32u	Number of connection structures allocated by the server
reserved_fds	32u	Number of misc fds used internally
cmd_get	64u	Cumulative number of retrieval reqs
cmd_set	64u	Cumulative number of storage reqs
cmd_flush	64u	Cumulative number of flush reqs
cmd_touch	64u	Cumulative number of touch reqs
get_hits	64u	Number of keys that have been requested and found present
get_misses	64u	Number of items that have been requested and not found
delete_misses	64u	Number of deletions reqs for missing keys
delete_hits	64u	Number of deletion reqs resulting in an item being removed.
incr_misses	64u	Number of incr reqs against missing keys.
incr_hits	64u	Number of successful incr reqs.
decr_misses	64u	Number of decr reqs against missing keys.
decr_hits	64u	Number of successful decr reqs.
cas_misses	64u	Number of CAS reqs against missing keys.
cas_hits	64u	Number of successful CAS reqs.
cas_badval	64u	Number of CAS reqs for which a key was found, but the CAS value did not match.
touch_hits	64u	Numer of keys that have been touched with a new expiration time
touch_misses	64u	Numer of items that have been touched and not found
auth_cmds	64u	Number of authentication commands handled, success or failure.
auth_errors	64u	Number of failed authentications.
evictions	64u	Number of valid items removed from cache to free memory for new items
reclaimed	64u	Number of times an entry was stored using memory from an expired entry
bytes_read	64u	Total number of bytes read by this server from network
bytes_written	64u	Total number of bytes sent by this server to network
limit_maxbytes	32u	Number of bytes this server is allowed to use for storage.
threads	32u	Number of worker threads requested. (see doc/threads.txt)
conn_yields	64u	Number of times any connection yielded to another due to hitting the -R limit.
hash_power_level	32u	Current size multiplier for hash table
hash_bytes	64u	Bytes currently used by hash tables
hash_is_expanding	bool	Indicates if the hash table is being grown to a new size
expired_unfetched	64u	Items pulled from LRU that were never touched by get/incr/append/etc before expiring
evicted_unfetched	64u	Items evicted from LRU that were never touched by get/incr/append/etc.
slab_reassign_running	bool	If a slab page is being moved
slabs_moved	64u	Total slab pages moved
crawler_reclaimed	64u	Total items freed by LRU Crawler
lrutail_reflocked	64u	Times LRU tail was found with active ref. Items moved to head to avoid OOM errors.

更詳細的內容能夠查看這裏:https://github.com/memcached/memcached/blob/master/doc/protocol.txt

另外，有關Memcached的經常使用命令及使用說明也能夠參考這篇文章：http://www.cnblogs.com/jeffwongishandsome/archive/2011/11/06/2238265.html