In
software engineering
Software engineering is a systematic engineering approach to software development.
A software engineer is a person who applies the principles of software engineering to design, develop, maintain, test, and evaluate computer software. The term '' ...
, a connection pool is a
cache
Cache, caching, or caché may refer to:
Places United States
* Cache, Idaho, an unincorporated community
* Cache, Illinois, an unincorporated community
* Cache, Oklahoma, a city in Comanche County
* Cache, Utah, Cache County, Utah
* Cache County ...
of
database connection A database connection is a facility in computer science that allows client software to talk to database server software, whether on the same machine or not. A connection is required to send commands and receive answers, usually in the form of a r ...
s maintained so that the connections can be reused when future requests to the database are required.
Connection pools are used to enhance the performance of executing commands on a database. Opening and maintaining a database connection for each user, especially requests made to a dynamic database-driven
website
A website (also written as a web site) is a collection of web pages and related content that is identified by a common domain name and published on at least one web server. Examples of notable websites are Google, Facebook, Amazon, and Wi ...
application, is costly and wastes resources. In connection pooling, after a connection is created, it is placed in the pool and it is used again so that a new connection does not have to be established. If all the connections are being used, a new connection is made and is added to the pool. Connection pooling also cuts down on the amount of time a user must wait to establish a connection to the database.
Applications
Web-based and
enterprise applications use an
application server to handle connection pooling.
Dynamic web page
A server-side dynamic web page is a web page whose construction is controlled by an application server processing server-side scripts. In server-side scripting, parameters determine how the assembly of every new web page proceeds, and includi ...
s without connection pooling open connections to database services as required and close them when the page is done servicing a particular request. Pages that use connection pooling, on the other hand, maintain open connections in a pool. When the page requires access to the database, it simply uses an existing connection from the pool, and establishes a new connection only if no pooled connections are available. This reduces the overhead associated with connecting to the database to service individual requests.
Local applications that need frequent access to databases can also benefit from connection pooling. Open connections can be maintained in local applications that do not need to service separate remote requests like application servers, but implementations of connection pooling can become complicated. A number of available
libraries
A library is a collection of Document, materials, books or media that are accessible for use and not just for display purposes. A library provides physical (hard copies) or electronic media, digital access (soft copies) materials, and may be a ...
implement connection pooling and related
SQL query pooling, simplifying the implementation of connection pools in database-intensive applications.
Administrators can configure connection pools with restrictions on the numbers of minimum connections, maximum connections and idle connections to optimize the performance of pooling in specific problem contexts and in specific environments.
See also
*
Object pool pattern
References
{{reflist
External links
*
Properly Handling Pooled JDBC Connections, blog post by Christopher Schultz
Database management systems