- 4 MySQL Native Driver (Mysqlnd)
- 4.1 Overview
- 4.2 Installation
- 4.3 Runtime Configuration
- 4.4 Incompatibilities
- 4.5 Persistent Connections
- 4.6 Statistics
- 4.7 Notes
- 4.8 MySQL Native Driver Plugin API
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Copyright 1997-2012 the PHP Documentation Group.
The MySQL Native Driver Plugin API is a feature of MySQL Native
Driver, or mysqlnd. Mysqlnd
plugins operate in the layer between PHP applications and the
MySQL server. This is comparable to MySQL Proxy. MySQL Proxy
operates on a layer between any MySQL client application, for
example, a PHP application and, the MySQL server.
Mysqlnd plugins can undertake typical MySQL
Proxy tasks such as load balancing, monitoring and performance
optimizations. Due to the different architecture and location,
mysqlnd plugins do not have some of MySQL
Proxy's disadvantages. For example, with plugins, there is no
single point of failure, no dedicated proxy server to deploy, and
no new programming language to learn (Lua).
A mysqlnd plugin can be thought of as an
extension to mysqlnd. Plugins can intercept the
majority of mysqlnd functions. The
mysqlnd functions are called by the PHP MySQL
extensions such as ext/mysql,
ext/mysqli, and PDO_MYSQL.
As a result, it is possible for a mysqlnd
plugin to intercept all calls made to these extensions from the
client application.
Internal mysqlnd function calls can also be
intercepted, or replaced. There are no restrictions on
manipulating mysqlnd internal function tables.
It is possible to set things up so that when certain
mysqlnd functions are called by the extensions
that use mysqlnd, the call is directed to the
appropriate function in the mysqlnd plugin. The
ability to manipulate mysqlnd internal function
tables in this way allows maximum flexibility for plugins.
Mysqlnd plugins are in fact PHP Extensions,
written in C, that use the mysqlnd plugin API
(which is built into MySQL Native Driver,
mysqlnd). Plugins can be made 100% transparent
to PHP applications. No application changes are needed because
plugins operate on a different layer. The
mysqlnd plugin can be thought of as operating
in a layer below mysqlnd.
The following list represents some possible applications of
mysqlnd plugins.
Load Balancing
Read/Write Splitting. An example of this is the PECL/mysqlnd_ms (Master Slave) extension. This extension splits read/write queries for a replication setup.
Failover
Round-Robin, least loaded
Monitoring
Query Logging
Query Analysis
Query Auditing. An example of this is the PECL/mysqlnd_sip (SQL Injection Protection) extension. This extension inspects queries and executes only those that are allowed according to a ruleset.
Performance
Caching. An example of this is the PECL/mysqlnd_qc (Query Cache) extension.
Throttling
Sharding. An example of this is the PECL/mysqlnd_mc (Multi Connect) extension. This extension will attempt to split a SELECT statement into n-parts, using SELECT ... LIMIT part_1, SELECT LIMIT part_n. It sends the queries to distinct MySQL servers and merges the result at the client.
MySQL Native Driver Plugins Available
There are a number of mysqlnd plugins already available. These include:
PECL/mysqlnd_mc - Multi Connect plugin.
PECL/mysqlnd_ms - Master Slave plugin.
PECL/mysqlnd_qc - Query Cache plugin.
PECL/mysqlnd_pscache - Prepared Statement Handle Cache plugin.
PECL/mysqlnd_sip - SQL Injection Protection plugin.
PECL/mysqlnd_uh - User Handler plugin.
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