Expose Engine.Searcher provider to ingest plugins.

server/src/main/java/org/elasticsearch/ingest/IngestService.java

@@ -30,11 +30,13 @@
 import org.elasticsearch.action.index.IndexRequest;
 import org.elasticsearch.action.ingest.DeletePipelineRequest;
 import org.elasticsearch.action.ingest.PutPipelineRequest;
+import org.elasticsearch.action.support.IndicesOptions;
 import org.elasticsearch.action.support.master.AcknowledgedResponse;
 import org.elasticsearch.cluster.AckedClusterStateUpdateTask;
 import org.elasticsearch.cluster.ClusterChangedEvent;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.ClusterStateApplier;
+import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
 import org.elasticsearch.cluster.metadata.MetaData;
 import org.elasticsearch.cluster.node.DiscoveryNode;
 import org.elasticsearch.cluster.service.ClusterService;
@@ -45,8 +47,12 @@
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.env.Environment;
 import org.elasticsearch.gateway.GatewayService;
+import org.elasticsearch.index.Index;
+import org.elasticsearch.index.IndexService;
 import org.elasticsearch.index.VersionType;
 import org.elasticsearch.index.analysis.AnalysisRegistry;
+import org.elasticsearch.index.shard.IndexShard;
+import org.elasticsearch.indices.IndicesService;
 import org.elasticsearch.plugins.IngestPlugin;
 import org.elasticsearch.script.ScriptService;
 import org.elasticsearch.threadpool.ThreadPool;
@@ -86,17 +92,43 @@ public class IngestService implements ClusterStateApplier {
 
     public IngestService(ClusterService clusterService, ThreadPool threadPool,
                          Environment env, ScriptService scriptService, AnalysisRegistry analysisRegistry,
-                         List<IngestPlugin> ingestPlugins) {
+                         List<IngestPlugin> ingestPlugins, IndicesService indicesService) {
         this.clusterService = clusterService;
         this.scriptService = scriptService;
+        final IndexNameExpressionResolver resolver = new IndexNameExpressionResolver();
         this.processorFactories = processorFactories(
             ingestPlugins,
             new Processor.Parameters(
                 env, scriptService, analysisRegistry,
                 threadPool.getThreadContext(), threadPool::relativeTimeInMillis,
                 (delay, command) -> threadPool.schedule(
                     command, TimeValue.timeValueMillis(delay), ThreadPool.Names.GENERIC
-                ), this
+                ), this, indexExpression -> {
+                    ClusterState state = clusterService.state();
+                    Index[] resolvedIndices = resolver.concreteIndices(state, IndicesOptions.STRICT_EXPAND_OPEN, indexExpression);
+                    if (resolvedIndices.length != 1) {
+                        throw new IllegalStateException("expression [" + indexExpression + "] can only point to a single concrete index");
+                    }
+                    Index index = resolvedIndices[0];
+
+                    // check if indexExpression matches with an alias that has a filter
+                    // There is no guarantee that alias filters are applied, so fail if this is the case.
+                    Set<String> indicesAndAliases = resolver.resolveExpressions(state, indexExpression);
+                    String[] aliasesWithFilter = resolver.filteringAliases(state, index.getName(), indicesAndAliases);
+                    if (aliasesWithFilter != null && aliasesWithFilter.length > 0) {
+                        throw new IllegalStateException("expression [" + indexExpression + "] points an alias with a filter");
+                    }
+
+                    IndexService indexService = indicesService.indexServiceSafe(index);
+                    int numShards = indexService.getMetaData().getNumberOfShards();
+                    if (numShards != 1) {
+                        throw new IllegalStateException("index [" + index.getName() + "] must have 1 shard, but has " + numShards +
+                            " shards");
+                    }
+
+                    IndexShard indexShard = indexService.getShard(0);
+                    return indexShard.acquireSearcher("ingest");
+                }
             )
         );
         this.threadPool = threadPool;

server/src/main/java/org/elasticsearch/ingest/Processor.java

@@ -22,11 +22,13 @@
 import org.elasticsearch.common.util.concurrent.ThreadContext;
 import org.elasticsearch.env.Environment;
 import org.elasticsearch.index.analysis.AnalysisRegistry;
+import org.elasticsearch.index.engine.Engine;
 import org.elasticsearch.script.ScriptService;
 import org.elasticsearch.threadpool.Scheduler;
 
 import java.util.Map;
 import java.util.function.BiFunction;
+import java.util.function.Function;
 import java.util.function.LongSupplier;
 
 /**
@@ -110,16 +112,24 @@ class Parameters {
          */
         public final BiFunction<Long, Runnable, Scheduler.ScheduledCancellable> scheduler;
 
+        /**
+         * Provides access to an engine searcher of a locally allocated index specified for the provided index.
+         *
+         * The locally allocated index must be have a single primary shard.
+         */
+        public final Function<String, Engine.Searcher> localShardSearcher;
+
         public Parameters(Environment env, ScriptService scriptService, AnalysisRegistry analysisRegistry,  ThreadContext threadContext,
                           LongSupplier relativeTimeSupplier, BiFunction<Long, Runnable, Scheduler.ScheduledCancellable> scheduler,
-            IngestService ingestService) {
+                          IngestService ingestService, Function<String, Engine.Searcher> localShardSearcher) {
             this.env = env;
             this.scriptService = scriptService;
             this.threadContext = threadContext;
             this.analysisRegistry = analysisRegistry;
             this.relativeTimeSupplier = relativeTimeSupplier;
             this.scheduler = scheduler;
             this.ingestService = ingestService;
+            this.localShardSearcher = localShardSearcher;
         }
 
     }

server/src/main/java/org/elasticsearch/node/Node.java

@@ -350,8 +350,6 @@ protected Node(
             final ClusterService clusterService = new ClusterService(settings, settingsModule.getClusterSettings(), threadPool);
             clusterService.addStateApplier(scriptModule.getScriptService());
             resourcesToClose.add(clusterService);
-            final IngestService ingestService = new IngestService(clusterService, threadPool, this.environment,
-                scriptModule.getScriptService(), analysisModule.getAnalysisRegistry(), pluginsService.filterPlugins(IngestPlugin.class));
             final DiskThresholdMonitor listener = new DiskThresholdMonitor(settings, clusterService::state,
                 clusterService.getClusterSettings(), client);
             final ClusterInfoService clusterInfoService = newClusterInfoService(settings, clusterService, threadPool, client,
@@ -421,6 +419,10 @@ protected Node(
                             threadPool, settingsModule.getIndexScopedSettings(), circuitBreakerService, bigArrays,
                             scriptModule.getScriptService(), client, metaStateService, engineFactoryProviders, indexStoreFactories);
 
+            final IngestService ingestService = new IngestService(clusterService, threadPool, this.environment,
+                scriptModule.getScriptService(), analysisModule.getAnalysisRegistry(),
+                pluginsService.filterPlugins(IngestPlugin.class), indicesService);
+
             final AliasValidator aliasValidator = new AliasValidator();
 
             final MetaDataCreateIndexService metaDataCreateIndexService = new MetaDataCreateIndexService(