[Backport 2.x] Register system index descriptors through SystemIndexP…

…lugin.getSystemIndexDescriptors (#1594)

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alerting/src/main/kotlin/org/opensearch/alerting/AlertingPlugin.kt

@@ -15,6 +15,7 @@ import org.opensearch.alerting.action.GetRemoteIndexesAction
 import org.opensearch.alerting.action.SearchEmailAccountAction
 import org.opensearch.alerting.action.SearchEmailGroupAction
 import org.opensearch.alerting.alerts.AlertIndices
+import org.opensearch.alerting.alerts.AlertIndices.Companion.ALL_ALERT_INDEX_PATTERN
 import org.opensearch.alerting.comments.CommentsIndices
 import org.opensearch.alerting.core.JobSweeper
 import org.opensearch.alerting.core.ScheduledJobIndices
@@ -103,6 +104,7 @@ import org.opensearch.commons.alerting.model.DocumentLevelTrigger
 import org.opensearch.commons.alerting.model.Monitor
 import org.opensearch.commons.alerting.model.QueryLevelTrigger
 import org.opensearch.commons.alerting.model.ScheduledJob
+import org.opensearch.commons.alerting.model.ScheduledJob.Companion.SCHEDULED_JOBS_INDEX
 import org.opensearch.commons.alerting.model.SearchInput
 import org.opensearch.commons.alerting.model.Workflow
 import org.opensearch.commons.alerting.model.remote.monitors.RemoteMonitorTrigger
@@ -114,6 +116,7 @@ import org.opensearch.core.xcontent.XContentParser
 import org.opensearch.env.Environment
 import org.opensearch.env.NodeEnvironment
 import org.opensearch.index.IndexModule
+import org.opensearch.indices.SystemIndexDescriptor
 import org.opensearch.monitor.jvm.JvmStats
 import org.opensearch.painless.spi.PainlessExtension
 import org.opensearch.painless.spi.Whitelist
@@ -124,6 +127,7 @@ import org.opensearch.plugins.ExtensiblePlugin
 import org.opensearch.plugins.ReloadablePlugin
 import org.opensearch.plugins.ScriptPlugin
 import org.opensearch.plugins.SearchPlugin
+import org.opensearch.plugins.SystemIndexPlugin
 import org.opensearch.repositories.RepositoriesService
 import org.opensearch.rest.RestController
 import org.opensearch.rest.RestHandler
@@ -139,7 +143,8 @@ import java.util.function.Supplier
  * It also adds [Monitor.XCONTENT_REGISTRY], [SearchInput.XCONTENT_REGISTRY], [QueryLevelTrigger.XCONTENT_REGISTRY],
  * [BucketLevelTrigger.XCONTENT_REGISTRY], [ClusterMetricsInput.XCONTENT_REGISTRY] to the [NamedXContentRegistry] so that we are able to deserialize the custom named objects.
  */
-internal class AlertingPlugin : PainlessExtension, ActionPlugin, ScriptPlugin, ReloadablePlugin, SearchPlugin, PercolatorPluginExt() {
+internal class AlertingPlugin : PainlessExtension, ActionPlugin, ScriptPlugin, ReloadablePlugin,
+    SearchPlugin, SystemIndexPlugin, PercolatorPluginExt() {
 
     override fun getContextWhitelists(): Map<ScriptContext<*>, List<Whitelist>> {
         val whitelist = WhitelistLoader.loadFromResourceFiles(javaClass, "org.opensearch.alerting.txt")
@@ -435,6 +440,13 @@ internal class AlertingPlugin : PainlessExtension, ActionPlugin, ScriptPlugin, R
         return listOf(TriggerScript.CONTEXT)
     }
 
+    override fun getSystemIndexDescriptors(settings: Settings): Collection<SystemIndexDescriptor> {
+        return listOf(
+            SystemIndexDescriptor(ALL_ALERT_INDEX_PATTERN, "Alerting Plugin system index pattern"),
+            SystemIndexDescriptor(SCHEDULED_JOBS_INDEX, "Alerting Plugin Configuration index")
+        )
+    }
+
     override fun reload(settings: Settings) {
         runner.reloadDestinationSettings(settings)
     }