3.3. Deploying a Fan-In Topology
The fan-in topology is the logical opposite of a master/slave topology. In a
fan-in topology, the data from two masters is combined together on one
slave. Fan-in topologies are often in situations where you have satellite
databases, maybe for sales or retail operations, and need to combine that
information together in a single database for processing.
Within the fan-in topology:
Figure 3.3. Topologies: Fan-in
Some additional considerations need to be made when using fan-in topologies:
If the same tables from each each machine are being merged together, it
is possible to get collisions in the data where auto increment is used.
The effects can be minimized by using increment offsets within the MySQL
auto-increment-offset = 1
auto-increment-increment = 4
Fan-in can work more effectively, and be less prone to problems with the
corresponding data by configuring specific tables at different sites.
For example, with two sites in New York and San Jose databases and
tables can be prefixed with the site name, i.e.
Alternatively, a filter can be configured to rename the database
sales dynamically to the
corresponding location based tables. See
Section 11.4.31, “Rename Filter” for more information.
Statement-based replication will work for most instances, but where your
statements are updating data dynamically within the statement, in fan-in
the information may get increased according to the name of fan-in
masters. Update your configuration file to explicitly use row-based
replication by adding the following to your
binlog-format = row
Triggers can cause problems during fan-in replication if two different
statements from each master and replicated to the slave and cause the
operations to be triggered multiple times. Tungsten Replication cannot prevent
triggers from executing on the concentrator host and there is no way to
selectively disable triggers. Check at the trigger level whether you are
executing on a master or slave. For more information, see
Section C.3.1, “Triggers”.
To create the configuration the masters and services must be specified, the
topology specification takes care of the actual configuration:
./tools/tpm install epsilon \
The description of each of the options is shown below; click the icon to
hide this detail:
Click the icon to show a detailed description of each argument.
For additional options supported for configuration with
tpm, see Chapter 10, The tpm Deployment Command.
If the installation process fails, check the output of the
/tmp/tungsten-configure.log file for
more information about the root cause.
Once the installation has been completed, the service will be started and
ready to use.