Bug 968361 - Improve database plugin design to support connection pooling
Thomas Segismont
tsegismo at redhat.com
Thu Jan 2 13:32:16 UTC 2014
Hi everyone,
I just pushed commit 2b810f1c9fa247a9d8ddf08d2b9ba93c9e1cf2a6 to master.
This changeset introduces a new API for database plugins and deprecates
the previous one. Compatibility with the previous API will be maintained
until next major version of RHQ.
The 'rhq-database-plugin' was based on
org.rhq.plugins.database.DatabaseComponent interface which encouraged
plugin authors to share a single JDBC connection across database
components. This was wrong for various reasons (connection leaks,
concurrent JDBC calls... etc).
The new API introduces three important classes:
* org.rhq.plugins.database.PooledConnectionProvider
* org.rhq.plugins.database.BasePooledConnectionProvider
* org.rhq.plugins.database.ConnectionPoolingSupport
BasePooledConnectionProvider is a base implementation of a
PooledConnectionProvider. Plugin authors should create a concrete
implementation of BasePooledConnectionProvider which overrides the
#getDriverClass() method. This is important if a database plugin embeds
a JDBC driver: the database-specific driver class must be loaded by the
child plugin classloader.
ConnectionPoolingSupport helps to manage the compatibility with the old
API. It's a contract that all new database resource components should
obey to. It declares the following methods:
* #supportsConnectionPooling()
* #getPooledConnectionProvider()
Results of calls to #supportsConnectionPooling()
#getPooledConnectionProvider() must be consistent. In practice, a top
level server database component should be able to create a
PooledConnectionProvider instance, and child servers and services should
indicate they support connection pooling only if their parent component
does.
The 'rhq-database-plugin' embeds the BoneCP library (JDBC connection
pooling) and its dependencies (Google's Guava). Child plugins will have
all the classes accessible as soon as they have this node in their
plugin descriptor:
===
<depends plugin="Database" useClasses="true"/>
===
This changeset includes the necessary changes to support connection
pooling in the Oracle, Postgres and MySQL plugins.
Thanks to Elias Ross for contributing the original patch from which this
changeset is derived.
Regards,
Thomas
Happy new year!
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