Publish Micrometer Metrics

This example demonstrates publishing metrics from GemFire to a monitoring system comprised of Prometheus and Grafana.

Steps to Run and Validate the Example

From the gemfire-examples/micrometerMetrics directory, run the start task to build the example and start a cluster. The cluster will have one locator, one server, and a single region. The locator and server will expose HTTP endpoints for Prometheus to scrape.
```
 $ ../gradlew start
```

Run the example to put entries into the region and verify that the HTTP endpoints are working.

 $ ../gradlew run

The previous command should produce output like the following:

 The entry count for region example-region on the server is 10.
 A Prometheus endpoint is running at http://localhost:9914.
 A Prometheus endpoint is running at http://localhost:9915.

To validate the example, navigate to the endpoints above in a browser. You should see text resembling the Prometheus exposition format.

(Optional) Viewing Metrics Using Prometheus and Grafana

Download and run Prometheus. Go to https://prometheus.io/download to download the latest release. Then, run the commands below to extract and run it:
```
 $ tar xvfz prometheus-*.tar.gz
 $ cd prometheus-*
 $ ./prometheus --config.file=../prometheus.yml
```
The provided prometheus.yml file configures Prometheus to scrape GemFire’s Prometheus endpoints at two-second intervals.
In a browser, navigate to http://localhost:9090/targets. This page shows GemFire’s Prometheus endpoints, and their state should be “UP” as shown below:
Navigate to http://localhost:9090/graph?g0.range_input=30m&g0.expr=geode_cache_entries&g0.tab=0. This page shows the result of the PromQL query geode_cache_entries over the last 30 minutes. It should show a value of “10” as the entry count for region example-region on the server:
Download and run Grafana. Add a new Prometheus data source with the address of the Prometheus server from the previous step. For detailed instructions, see Grafana’s Getting Started Guide.
Once you have added the Prometheus data source, you can import this dashboard from Grafana.com.

To import, select the “plus” icon on the left-hand side and choose the “Import” option. Use the ID from the link above for the dashboard and specify the Prometheus data source you created in the last step.

Clean Up

Shut down the cluster.
```
 $ cd ..
 $ ../gradlew stop
```