alias in rollup target_index field

src/main/kotlin/org/opensearch/indexmanagement/IndexManagementPlugin.kt

@@ -372,7 +372,7 @@ class IndexManagementPlugin : JobSchedulerExtension, NetworkPlugin, ActionPlugin
         this.indexNameExpressionResolver = indexNameExpressionResolver
 
         val skipFlag = SkipExecution(client)
-        RollupFieldValueExpressionResolver.registerScriptService(scriptService)
+        RollupFieldValueExpressionResolver.registerServices(scriptService, clusterService)
         val rollupRunner = RollupRunner
             .registerClient(client)
             .registerClusterService(clusterService)

src/main/kotlin/org/opensearch/indexmanagement/rollup/RollupMapperService.kt

@@ -14,13 +14,16 @@ import org.opensearch.action.admin.indices.create.CreateIndexRequest
 import org.opensearch.action.admin.indices.create.CreateIndexResponse
 import org.opensearch.action.admin.indices.mapping.get.GetMappingsRequest
 import org.opensearch.action.admin.indices.mapping.get.GetMappingsResponse
+import org.opensearch.action.admin.indices.mapping.put.PutMappingRequest
+import org.opensearch.action.admin.indices.settings.put.UpdateSettingsRequest
 import org.opensearch.action.support.IndicesOptions
 import org.opensearch.action.support.master.AcknowledgedResponse
 import org.opensearch.client.Client
 import org.opensearch.cluster.metadata.IndexNameExpressionResolver
 import org.opensearch.cluster.metadata.MappingMetadata
 import org.opensearch.cluster.service.ClusterService
 import org.opensearch.common.settings.Settings
+import org.opensearch.common.xcontent.XContentType
 import org.opensearch.indexmanagement.IndexManagementIndices
 import org.opensearch.indexmanagement.common.model.dimension.DateHistogram
 import org.opensearch.indexmanagement.common.model.dimension.Histogram
@@ -33,7 +36,9 @@ import org.opensearch.indexmanagement.rollup.model.RollupJobValidationResult
 import org.opensearch.indexmanagement.rollup.settings.LegacyOpenDistroRollupSettings
 import org.opensearch.indexmanagement.rollup.settings.RollupSettings
 import org.opensearch.indexmanagement.rollup.util.RollupFieldValueExpressionResolver
+import org.opensearch.indexmanagement.rollup.util.getRollupJobs
 import org.opensearch.indexmanagement.rollup.util.isRollupIndex
+import org.opensearch.indexmanagement.rollup.util.isTargetIndexAlias
 import org.opensearch.indexmanagement.util.IndexUtils.Companion._META
 import org.opensearch.indexmanagement.util.IndexUtils.Companion.getFieldFromMappings
 import org.opensearch.transport.RemoteTransportException
@@ -53,26 +58,70 @@ class RollupMapperService(
     // If the index already exists we need to verify it's a rollup index,
     // confirm it does not conflict with existing jobs and is a valid job
     @Suppress("ReturnCount")
-    private suspend fun validateAndAttemptToUpdateTargetIndex(rollup: Rollup, targetIndexResolvedName: String): RollupJobValidationResult {
-        if (!isRollupIndex(targetIndexResolvedName, clusterService.state())) {
+    private suspend fun validateAndAttemptToUpdateTargetIndex(
+        rollup: Rollup,
+        targetIndexResolvedName: String,
+        hasLegacyPlugin: Boolean
+    ): RollupJobValidationResult {
+        /**
+         * Target Index is valid alias if either all backing indices have this job in _meta
+         * or there isn't any rollup job present in _meta
+         */
+        var isValidAlias = isTargetIndexValidAlias(rollup, targetIndexResolvedName)
+        if (rollup.isTargetIndexAlias() && isValidAlias) {
+            // During first run on alias, backing index is not prepared. We should set it up here. (settings, mappings, _meta)
+            if (!isRollupIndex(targetIndexResolvedName, clusterService.state())) {
+                return prepareTargetIndex(rollup, targetIndexResolvedName, hasLegacyPlugin)
+            }
+        } else if (rollup.isTargetIndexAlias() && !isValidAlias) {
+            return RollupJobValidationResult.Failure("Target index alias [${rollup.targetIndex}] validation failed")
+        } else if (!isRollupIndex(targetIndexResolvedName, clusterService.state())) {
             return RollupJobValidationResult.Invalid("Target index [$targetIndexResolvedName] is a non rollup index")
         }
-
         return when (val jobExistsResult = jobExistsInRollupIndex(rollup, targetIndexResolvedName)) {
             is RollupJobValidationResult.Valid -> jobExistsResult
             is RollupJobValidationResult.Invalid -> updateRollupIndexMappings(rollup, targetIndexResolvedName)
             is RollupJobValidationResult.Failure -> jobExistsResult
         }
     }
 
+    @Suppress("ReturnCount")
+    suspend fun isTargetIndexValidAlias(rollup: Rollup, targetIndexResolvedName: String): Boolean {
+
+        if (!RollupFieldValueExpressionResolver.indexAliasUtils.hasAlias(targetIndexResolvedName)) {
+            return false
+        }
+
+        val rollupJobs = clusterService.state().metadata.index(targetIndexResolvedName).getRollupJobs()
+        if (rollupJobs != null &&
+            (rollupJobs.size > 1 || rollupJobs[0].id != rollup.id)
+        ) {
+            logger.error("If target_index is alias, backing index must be empty: $targetIndexResolvedName")
+            return false
+        }
+
+        // All other backing indices have to have this rollup job in _META field and it has to be the only one!
+        val backingIndices = RollupFieldValueExpressionResolver.indexAliasUtils.getBackingIndicesForAlias(rollup.targetIndex)
+        backingIndices?.forEach {
+            if (it.index.name != targetIndexResolvedName) {
+                val rollupJobs = clusterService.state().metadata.index(it.index.name).getRollupJobs()
+                if (rollupJobs == null || rollupJobs.size > 1 || rollupJobs[0].id != rollup.id) {
+                    logger.error("If target_index is alias, all backing indicies must have only this rollup job present in _meta!")
+                    return false
+                }
+            }
+        }
+        return true
+    }
+
     // This creates the target index if it doesn't already else validate the target index is rollup index
     // If the target index mappings doesn't contain rollup job attempts to update the mappings.
     // TODO: error handling
     @Suppress("ReturnCount")
     suspend fun attemptCreateRollupTargetIndex(job: Rollup, hasLegacyPlugin: Boolean): RollupJobValidationResult {
         val targetIndexResolvedName = RollupFieldValueExpressionResolver.resolve(job, job.targetIndex)
         if (indexExists(targetIndexResolvedName)) {
-            return validateAndAttemptToUpdateTargetIndex(job, targetIndexResolvedName)
+            return validateAndAttemptToUpdateTargetIndex(job, targetIndexResolvedName, hasLegacyPlugin)
         } else {
             val errorMessage = "Failed to create target index [$targetIndexResolvedName]"
             return try {
@@ -96,6 +145,52 @@ class RollupMapperService(
         }
     }
 
+    suspend fun addRollupSettingToIndex(targetIndexResolvedName: String, hasLegacyPlugin: Boolean): Boolean {
+        val settings = if (hasLegacyPlugin) {
+            Settings.builder().put(LegacyOpenDistroRollupSettings.ROLLUP_INDEX.key, true).build()
+        } else {
+            Settings.builder().put(RollupSettings.ROLLUP_INDEX.key, true).build()
+        }
+        val resp: AcknowledgedResponse = client.admin().indices().suspendUntil {
+            updateSettings(UpdateSettingsRequest(settings, targetIndexResolvedName), it)
+        }
+        return resp.isAcknowledged
+    }
+    @Suppress("ReturnCount")
+    suspend fun prepareTargetIndex(rollup: Rollup, targetIndexResolvedName: String, hasLegacyPlugin: Boolean): RollupJobValidationResult {
+        var errorMessage = ""
+        try {
+            // 1. First we need to add index.plugins.rollup_index setting to index
+            if (addRollupSettingToIndex(targetIndexResolvedName, hasLegacyPlugin) == false) {
+                return RollupJobValidationResult.Invalid("Failed to update rollup settings for target index: [$targetIndexResolvedName]")
+            }
+
+            // 2. Put rollup mappings
+            val putMappingRequest: PutMappingRequest =
+                PutMappingRequest(targetIndexResolvedName).source(IndexManagementIndices.rollupTargetMappings, XContentType.JSON)
+            val respMappings: AcknowledgedResponse = client.admin().indices().suspendUntil {
+                putMapping(putMappingRequest, it)
+            }
+            if (!respMappings.isAcknowledged) {
+                return RollupJobValidationResult.Invalid("Failed to put initial rollup mappings for target index [$targetIndexResolvedName]")
+            }
+            // 3.
+            errorMessage = "Failed to update mappings for target index [$targetIndexResolvedName]"
+            updateRollupIndexMappings(rollup, targetIndexResolvedName)
+        } catch (e: RemoteTransportException) {
+            val unwrappedException = ExceptionsHelper.unwrapCause(e) as Exception
+            logger.error(errorMessage, unwrappedException)
+            RollupJobValidationResult.Failure(errorMessage, unwrappedException)
+        } catch (e: OpenSearchSecurityException) {
+            logger.error("$errorMessage because ", e)
+            RollupJobValidationResult.Failure("$errorMessage - missing required cluster permissions: ${e.localizedMessage}", e)
+        } catch (e: Exception) {
+            logger.error("$errorMessage because ", e)
+            RollupJobValidationResult.Failure(errorMessage, e)
+        }
+        return RollupJobValidationResult.Valid
+    }
+
     private suspend fun createTargetIndex(targetIndexName: String, hasLegacyPlugin: Boolean): CreateIndexResponse {
         val settings = if (hasLegacyPlugin) {
             Settings.builder().put(LegacyOpenDistroRollupSettings.ROLLUP_INDEX.key, true).build()

src/main/kotlin/org/opensearch/indexmanagement/rollup/settings/RollupSettings.kt

@@ -39,7 +39,7 @@ class RollupSettings {
             "index.plugins.rollup_index",
             LegacyOpenDistroRollupSettings.ROLLUP_INDEX,
             Setting.Property.IndexScope,
-            Setting.Property.InternalIndex
+            Setting.Property.Dynamic
         )
 
         val ROLLUP_INGEST_BACKOFF_MILLIS: Setting<TimeValue> = Setting.positiveTimeSetting(

src/main/kotlin/org/opensearch/indexmanagement/rollup/util/RollupFieldValueExpressionResolver.kt

@@ -5,6 +5,9 @@
 
 package org.opensearch.indexmanagement.rollup.util
 
+import org.opensearch.cluster.metadata.IndexAbstraction
+import org.opensearch.cluster.metadata.IndexMetadata
+import org.opensearch.cluster.service.ClusterService
 import org.opensearch.common.xcontent.XContentFactory
 import org.opensearch.indexmanagement.indexstatemanagement.util.XCONTENT_WITHOUT_TYPE
 import org.opensearch.indexmanagement.opensearchapi.toMap
@@ -19,22 +22,58 @@ object RollupFieldValueExpressionResolver {
     private val validTopContextFields = setOf(Rollup.SOURCE_INDEX_FIELD)
 
     private lateinit var scriptService: ScriptService
-
+    private lateinit var clusterService: ClusterService
+    lateinit var indexAliasUtils: IndexAliasUtils
     fun resolve(rollup: Rollup, fieldValue: String): String {
         val script = Script(ScriptType.INLINE, Script.DEFAULT_TEMPLATE_LANG, fieldValue, mapOf())
 
         val contextMap = rollup.toXContent(XContentFactory.jsonBuilder(), XCONTENT_WITHOUT_TYPE)
             .toMap()
             .filterKeys { key -> key in validTopContextFields }
 
-        val compiledValue = scriptService.compile(script, TemplateScript.CONTEXT)
+        var compiledValue = scriptService.compile(script, TemplateScript.CONTEXT)
             .newInstance(script.params + mapOf("ctx" to contextMap))
             .execute()
 
-        return if (compiledValue.isBlank()) fieldValue else compiledValue
+        if (indexAliasUtils.isAlias(compiledValue)) {
+            compiledValue = indexAliasUtils.getWriteIndexNameForAlias(compiledValue)
+        }
+
+        return if (compiledValue.isNullOrBlank()) fieldValue else compiledValue
+    }
+
+    fun registerServices(scriptService: ScriptService, clusterService: ClusterService) {
+        this.scriptService = scriptService
+        this.clusterService = clusterService
+        this.indexAliasUtils = IndexAliasUtils(clusterService)
     }
 
-    fun registerScriptService(scriptService: ScriptService) {
+    fun registerServices(scriptService: ScriptService, clusterService: ClusterService, indexAliasUtils: IndexAliasUtils) {
         this.scriptService = scriptService
+        this.clusterService = clusterService
+        this.indexAliasUtils = indexAliasUtils
+    }
+
+    open class IndexAliasUtils(val clusterService: ClusterService) {
+
+        open fun hasAlias(index: String): Boolean {
+            val aliases = this.clusterService.state().metadata().indices.get(index)?.aliases
+            if (aliases != null) {
+                return aliases.size() > 0
+            }
+            return false
+        }
+
+        open fun isAlias(index: String): Boolean {
+            return this.clusterService.state().metadata().indicesLookup?.get(index) is IndexAbstraction.Alias
+        }
+
+        open fun getWriteIndexNameForAlias(alias: String): String? {
+            return this.clusterService.state().metadata().indicesLookup?.get(alias)?.writeIndex?.index?.name
+        }
+
+        open fun getBackingIndicesForAlias(alias: String): MutableList<IndexMetadata>? {
+            return this.clusterService.state().metadata().indicesLookup?.get(alias)?.indices
+        }
     }
 }

src/main/kotlin/org/opensearch/indexmanagement/rollup/util/RollupUtils.kt

@@ -73,6 +73,10 @@ fun isRollupIndex(index: String, clusterState: ClusterState): Boolean {
     return false
 }
 
+fun Rollup.isTargetIndexAlias(): Boolean {
+    return RollupFieldValueExpressionResolver.indexAliasUtils.isAlias(targetIndex)
+}
+
 fun Rollup.getRollupSearchRequest(metadata: RollupMetadata): SearchRequest {
     val query = if (metadata.continuous != null) {
         RangeQueryBuilder(this.getDateHistogram().sourceField)