GemFire XD supports propagating create, read, update, and delete operations across
multiple distributed systems. You can use this feature to keep multiple GemFire XD clusters in
synch with each other over a wide area network.
Note: DDL operations and procedure execution are not propagated across WAN boundaries. See Multi-site (WAN) Deployment for more information.
How Multi-site Systems Work
Each distributed system in a multi-site configuration operates independently of the other connected systems. Each system can be configured as necessary for the resources available at the local site, as well as the local topology (peer-to-peer and/or client-server).
A multi-site installation consists of two or more distributed systems. Each site is its own distributed system and has one or more logical connections to other sites, called gateways.
Managing Schema Changes
The GemFire XD WAN replication and DBSynchronizer features are designed to keep tables having identical schemas in sync with one another. However, DDL operations such as ALTER TABLE are never propagated over a WAN or to a configured back-end database. If you need to change the schema of a table after configuring WAN or DBSynchronizer replication, use this procedure to avoid excessive synchronization failures.
Resolving WAN Errors
You can optionally create a GatewayEventErrorHandler implementation to respond to errors that occur when GemFire XD cannot apply a DML event that was delivered from another site over a WAN, or an event that could not be applied using a DBSynchronizer configuration.
How Multi-site Event Distribution Works
In a multi-site configuration, GemFire XD distributes table DML operations between remote distributed systems, with a minimum impact on each system's performance. DML events are distributed only for the tables that you configure for replication by using a gateway receiver.