PHP memcached client memcached_PHP tutorial-PHP Tutorial-php.cn

PHP memcached client memcached_PHP tutorial

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Release： 2016-07-21 15:27:58

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The official homepage of memcache: http://pecl.php.net/package/memcache
The official homepage of memcached: http://pecl.php.net/package/memcached

The following is how I installed Memcached Version of the process record of the PHP module:

wget http://download.tangent.org/libmemcached-0.48.tar.gz
tar zxf libmemcached-0.48.tar.gz
cd libmemcached- 0.48
./configure --prefix=/usr/local/libmemcached --with-memcached
make
make install

wget http://pecl.php.net/get/ memcached-1.0.2.tgz
tar zxf memcached-1.0.2.tgz
cd memcached-1.0.2
/usr/local/webserver/php/bin/phpize
./configure - -enable-memcached --with-php-config=/usr/local/webserver/php/bin/php-config --with-libmemcached-dir=/usr/local/libmemcached
make
make install

Add
extension=memcached.so to php.ini
Complete

Another:
When installing libmemcached, if you only use ./configure, you may be prompted:
checking for memcached… no
configure: error: “could not find memcached binary”

The two are almost identical in use.

Copy code The code is as follows:

 
$mem = new Memcache; 
$mem->addServer($memcachehost , '11211'); 
$mem->addServer($memcachehost, '11212'); 
$mem->set('hx','9enjoy'); 
echo $mem- >get('hx'); 

Copy code The code is as follows:

 
$md = new Memcached; 
$servers = array( 
array($memcachehost, '11211'), 
array($memcachehost, '11212') 
); 
$md->addServers ($servers); 
$md->set('hx','9enjoy'); 
echo $md->get('hx'); 

memcached There are many more methods than memcache, such as getMulti, getByKey, addServers, etc.
Memcached does not have the connect method of memcache, and it does not currently support long connections.
Memcached supports Binary Protocol, but memcache does not, which means memcached will have higher performance.
Memcache is implemented natively and supports the coexistence of OO and non-OO interfaces. memcached uses libmemcached and only supports OO interfaces.
More detailed differences: http://code.google.com/p/memcached/wiki/PHPClientComparison

The memcached server is a centralized caching system, and the distributed implementation method is Determined by the client.
The memcached distribution algorithm generally has two options:
1. According to the result of hash(key), the remainder of the modular connection number determines which node to store, that is, hash(key)% sessions.size(), This algorithm is simple, fast and performs well. However, this algorithm has a shortcoming, that is, when memcached nodes are added or deleted, the original cached data will become invalid on a large scale, and the hit rate will be greatly affected. If there are many nodes and cached data, the cost of rebuilding the cache will be too high, so With the second algorithm.
2. Consistent Hashing, consistent hashing algorithm, its node search process is as follows:
First find the hash value of the memcached server (node), and configure it to the circle (continuum) of 0~232 superior. Then use the same method to find the hash value of the key storing the data and map it to the circle. It then searches clockwise starting from the location where the data is mapped, and saves the data to the first server found. If the server is still not found after exceeding 2 to the power of 32, it will be saved to the first memcached server.

memcache uses the first method without any configuration. To implement the first method, memcached seems to use (unconfirmed):
$md->setOption(Memcached::OPT_HASH, Memcached::HASH_CRC);

The second consistent hash Algorithm:

memcache Add

Copy code The code is as follows:

 
Memcache.hash_strategy =consistent 
Memcache.hash_function =crc32 

Add memcached in the program (unconfirmed)

Copy code The code is as follows :

 
$md->setOption(Memcached::OPT_DISTRIBUTION, Memcached::DISTRIBUTION_CONSISTENT); 
$md->setOption(Memcached::OPT_HASH, Memcached::HASH_CRC); 
 or 
$mem->setOption(Memcached::OPT_DISTRIBUTION,Memcached::DISTRIBUTION_CONSISTENT); 
$mem->setOption(Memcached::OPT_LIBKETAMA_COMPATIBLE,true); 

Some reference documents:
memcached distribution test report (hash function selection in the case of consistent hashing):
http://www.iteye.com/topic/346682
php module memcache The difference with memcached: http://www.jb51.net/article/27366.htm
PHP module: Memcached > Memcache: http://www.jb51.net/article/27367.htm

20110509@@UPDATE:
If you install libmemcached, the following error message appears:
make[2]: *** [clients/ms_conn.o] Error 1
make[2]: Leaving directory `/www /soft/libmemcached-0.48'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/www/soft/libmemcached-0.48'
make: *** [all] Error 2

You can add --disable-64bit CFLAGS="-O3 -march=i686" when configure.
That is: ./configure --prefix=/usr/local /libmemcached --with-memcached --disable-64bit CFLAGS="-O3 -march=i686"