Apache Geode

How Distribution Works

To use distributed and replicated regions, you should understand how they work and your options for managing them.

Note: The management of replicated and distributed regions supplements the general information for managing data regions provided in Basic Configuration and Programming. See also org.apache.geode.cache.PartitionAttributes.

A distributed region automatically sends entry value updates to remote caches and receives updates from them.

• Distributed entry updates come from the Region put and create operations (the creation of an entry with a non-null value is seen as an update by remote caches that already have the entry key). Entry updates are distributed selectively - only to caches where the entry key is already defined. This provides a pull model of distribution, compared to the push model that you get with replication.
• Distribution alone does not cause new entries to be copied from remote caches.
• A distributed region shares cache loader and cache writer application event handler plug-ins across the cluster.

In a distributed region, new and updated entry values are automatically distributed to remote caches that already have the entries defined.

Step 1: The application updates or creates the entry. At this point, the entry in the M1 cache may not yet exist.

Step 2: The new value is automatically distributed to caches holding the entry.

Step 3: The entry’s value is the same throughout the cluster.