[docs] Document config properties required to set up presto-plan-checker-router-plugin

Author: pdabre12

presto-plan-checker-router-plugin/README.md

@@ -0,0 +1,32 @@
+# Example - Presto Plan Checker Router Scheduler Plugin
+This package contains a custom scheduler plugin - Presto Plan Checker Router Scheduler Plugin.
+
+## Add the Custom Scheduler Plugin to the Presto Router
+Place the plugin jar and all the dependent jars for the plugin in the `plugin` directory relative to the Presto install directory.
+
+Create a configuration file for this plugin. The file must be named `router-scheduler.properties` and must be in the `etc/router-config/` directory relative to the Presto install directory.
+
+Set the scheduler name to `CUSTOM_PLUGIN_SCHEDULER` in `etc/router-config.json`.  
+``scheduler``: ``CUSTOM_PLUGIN_SCHEDULER``
+
+## Main Classes:
+* `RouterSchedulerPlugin` - Custom Scheduler Plugin class to be loaded by the Router plugin manager.  
+  This class implements the interface `com.facebook.presto.spi.RouterPlugin`.
+* `PlanCheckerRouterPluginSchedulerFactory` - Factory for creating plan checker custom scheduler.  
+  This class implements the interface `com.facebook.presto.spi.SchedulerFactory`.
+* `PlanCheckerRouterPluginScheduler` - Plan checker custom scheduler implementing the scheduling logic for clusters.  
+  This class implements the interface `com.facebook.presto.spi.router.Scheduler`.  
+
+## Configuration:
+The following configuration properties must be set in `etc/router-config/router-scheduler.properties`:
+
+| Property Name            | Type   | Description                                                             |                   
+|--------------------------|--------|-------------------------------------------------------------------------|
+| router-scheduler.name    | String | The name of the custom scheduler factory                                |
+|                          |        | Example: `router-scheduler.name=plan-checker`                           |
+| plan-check-clusters-uris | String | The URIs of the plan checker clusters.                                  |                                           |
+| router-java-url          | String | The router URI dedicated to java clusters.                              |
+| router-native-url        | String | The router URI dedicated to native clusters.                            |
+| client-request-timeout   | String | The maximum time the client will wait for a response before timing out. |
+|                          |        | Default : `2 minutes`                                                   |
+