This is a simple example that demonstrates persistent regions.

The data for a region resides in memory in the JVM for the server. When a region is persistent, the data for that region is also preserved in a disk store. The disk store uses a directory in a file system to save the operations on regions. Unlike non-persistent regions, the data for a persistent region is available even after a period where no servers for that region are running.

This example assumes you have installed Java and Geode.

1. From the geode-examples/persistence directory, build the example, and run unit tests.

    $ ../gradlew build
   

2. Next start a locator, start a server, create a disk store, and create a persistent region.

    $ gfsh run --file=scripts/start.gfsh
   

3. Run the example to increment an entry the region.

    $ ../gradlew run
   

4. Observe that the first time an initial value is used.

    Initialized counter to 0
    Incremented counter to 1
   

5. Restart down the server.

    $ gfsh run --file=scripts/restart.gfsh
   

6. Run the example to increment an entry the region.

    $ ../gradlew run
   

7. Observe that the second time the previous value is used.

    Retrieved counter of 1
    Incremented counter to 2
   

8. Shut down the system.

    $ gfsh run --file=scripts/stop.gfsh