How to best use memcached

The difference between the two can be clearly seen in the official PHP manual

Memcache is developed entirely within the PHP framework, and Memecached uses libmemcached. From the manual, memcached will have several more methods than memcache, and the way to use them is similar.

Memcache is implemented natively, but Memached using libmemcached only supports OO interfaces, while Memcache is the coexistence of OO and non-OO interfaces, and this lib will definitely follow up as the memcached server side improves in the future. Memcache, on the other hand, may not be able to follow up on time.

Memcached, and another very commendable point, is that the flag is not set at the time of operation. Instead, there is a unified setoption(). memcached implements more of the memcached protocol (based on the libmemcached library, after all).

Here's another comparison table, and it's clear that using memcached is a lot more reassuring.

The big difference is that memcached supports binary protocol, while memcache does not, which means that memcached will have higher performance. However, it's also important to note that memcached doesn't support persistent connections at this time.

Key-value pairs are stored. It's essentially a big one.

The maximum length of a key is 255 characters and the maximum expiration time is 30 days.

2.Its memory model is as follows: MemCache pre-partitions the available memory space (slab), and each partition is divided into chunks with a maximum of 1 m, but the blocks in the same partition are large.

Small is fixed. Then, when inserting data, it will find the most suitable block according to the size of the data, and then insert it, of course, there will be some memory waste, but it can reduce memory fragmentation to a certain extent, and in general, the benefits are greater than.

Fraud. When the memory of memcache is full, it clears the old data based on the principle of lru idle and expired minimum access. And it uses lazy deletion, and it doesn't provide monitoring data expiration.

When the data of a certain key is queried, if it expires, it will be discarded directly.

3.Please refer to the details for details.

By default, PHP or MySQL are installed and called using plugins.

The atoms processed by memcached are each (key, value) pair (hereinafter referred to as kv pair), and the key will be converted into a hash-key through a hash algorithm, which is easy to find, compare, and hash as much as possible. At the same time, memcached uses a secondary hash, which is maintained by a large hash table.

Memcached consists of two core components: server and client, and in a memcached query, the client first calculates the hash value of the key to determine the server location of the kv pair. When the server is determined, the client sends a query request to the corresponding server to find the exact data.

For example, consider the following scenario, where there are three clients C1, C2, and C3, and three MSs are S1, S2, and S3

Set the kv pair.

c1 wants to set key="com" and value="iqiyi".

C1 gets the server list and converts the key to the hash, and determines the location of the KV pair according to the hash value.

S2 was chosen.

C1 connects to S2, and S2 receives the request and saves (key="com",value="iqiyi").

Get kv pairs.

c3 wants to get the value of key="com".

C3 uses the same hash algorithm to calculate the hash value and determines that the value of key="aa" exists on S2.

c3 connects to s2 and gets value="iqiyi" from s2

Any other request from c1, c2, c3 to get the value of key="com" will be sent to s2

Memcache is a type of caching server software, and the computer on which it is installed is called a caching server.

The memcache cache server is used to alleviate the load pressure of relational databases (such as MySQL), after accessing the MySQL database (select) for the first time, the obtained data is put into the cache server, a life cycle is set (for example, 7 days), and then all statements that access the data within 7 days do not need to be queried in the data, and are directly retrieved from the cache server.

The memcache in PHP you are asking about is a kind of client, and the client is used to access the server (e.g. with Internet Explorer to access **, IE is the client). To be more specific, MemCache in PHP is an extension that allows you to access the MemCache server using the MemCache class instance object and various methods of the Memcache object by enabling the Memcache extension in the configuration file of the PHP installation directory.

Example: $mem = new memcache(); Instantiate an object.

$mem->connect("IP address", port number); Connect to the memcache server.

mem->connect("localhost",11211);Connect to the memcache server.

Add data, if the key name already exists, the addition fails.

res = $mem->add('name','xiaoqian',memcache_compressed,3600);

var_dump($res);

Get the data. str = $mem->get('name');

var_dump($str);

For more information on how to open the follow-up of the extension, you can just take a look at it in this word document I uploaded.

Memcache itself is a distributed caching system, which resides in memory in the form of key-value, and is generally used for caching of ** or databases.

In particular, memcache is a good choice for caching in the following scenarios:

1.Frequently Accessed Data2Data with relatively low security requirements3Frequently updated small tables (such as user status tables, item inventory, etc.).