C-JDBC is a database cluster middleware that allows any Java
™ application (standalone application, servlet or
EJB
™ container, ...) to transparently access a
cluster of databases through JDBC
™. You do not have
to modify client applications, application servers or database server software.
You just have to ensure that all database accesses are performed through
C-JDBC.
C-JDBC is a free
, open source
project of the ObjectWeb Consortium
. It is
licensed under the GNU Lesser General Public License
(LGPL).
1.2. What do I need to
use C-JDBC?
In order to use C-JDBC, you will need:
-
a client application that accesses a database through JDBC,
-
a JDK
™ 1.3 (or greater) compliant Java Virtual Machine
™ (JVM)[1
]
,
-
a database with a JDBC driver (type 1, 2, 3 or 4) or an ODBC driver used with
the JDBC-ODBC bridge.
-
a network supporting TCP/IP communications between your cluster
nodes.
|
Note
If your client application uses ODBC, it is possible to use an ODBC-JDBC
bridge such as the unixODBC
provided by Easysoft.
|
1.3. Why should I use
C-JDBC?
You have a Java application or a Java-based application server that accesses
one or several databases. The database tier becomes the bottleneck of your
application or it is a single point of failure or both. C-JDBC can help you
resolve these problems by providing:
-
performance scalability by adding database nodes and balacing the load among
these nodes.
-
high availability of the database tier, i.e. C-JDBC tolerates database
crashes and offers transparent failover using database replication
techniques.
-
improved performance with fine grain query caching and transparent connection
pooling.
-
SQL traffic logging for performance monitoring and analysis.
-
support for clusters of heterogenous database
engines.
C-JDBC provides a flexible architecture that allows you to achieve
scalability, high availability and failover with your database tier. C-JDBC
implements the concept of RAIDb: Redundant Array of
Inexpensive Databases
(see Section 10, “RAIDb Basics”
). The database is distributed
and replicated among several nodes and C-JDBC load balances the queries between
these nodes.
C-JDBC provides a generic JDBC driver to be used by the clients (see Section 4, “C-JDBC Driver”
).
This driver forwards the SQL requests to the C-JDBC controller (see Section 6, “C-JDBC
controller”
) that balances them on a cluster of databases (reads are load
balanced and writes are broadcasted). C-JDBC can be used with any RDBMS
(Relational DataBase Management System) providing a JDBC driver, that is to say
almost all existing open source and commercial databases. Figure 1, “C-JDBC principle”
gives an
overview of the C-JDBC principle.
C-JDBC allows to build any cluster configuration including mixing database
engines from different vendors. The main features provided by C-JDBC are
performance scalability, fault tolerance and high availability. Additional
features such as monitoring, logging, SQL requests caching are provided as
well.
The architecture is widely open to allow anyone to plug custom requests
schedulers, load balancers, connection managers, caching policies, ...
From a software point of view, C-JDBC is an open-source software licensed
under LGPL which means that it is free of charge for any usage (personal or
commercial). If you are using commercial RDBMS (such as Oracle, DB2, ...), you
will have to buy extra licenses for the nodes where you install replicas of the
database. But you can possibly use open-source databases to host replicas of
your main database.
You need to buy extra machines if you want more performance and more fault
tolerance. C-JDBC has been designed to work with standard off-the-shelf
workstations because it primarily targets low cost open-source solutions but it
can work as well with large SMP machines. A standard Ethernet network is
sufficient to achieve good performance.
1.6. What kind of
modifications are needed?
You do not have to change anything
to
your application or your database.
You only have to update the JDBC driver configuration used by your
application (usually it is just a configuration file update) and to setup a
C-JDBC configuration file (see Section 11, “Virtual database
configuration”
).
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