[Search pipelines] Pass "adhocness" flag to processor factories

A named search pipeline may be created with a PUT request, while
an "anonymous" or "ad hoc" search pipeline can be defined in the
search request source. In the latter case, we don't want to create any
"resource-heavy" processors, since they're potentially increasing the
cost of every search request, whereas names pipeline processors get
reused.

This change passes a configuration flag to a processor factory if it's
being called as part of an ad hoc pipeline. The factory can use that
information to avoid allocating expensive resources (maybe by throwing
an exception instead).

Signed-off-by: Michael Froh <froh@amazon.com>

CHANGELOG.md

@@ -120,6 +120,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Compress and cache cluster state during validate join request ([#7321](https://github.com/opensearch-project/OpenSearch/pull/7321))
 - [Snapshot Interop] Add Changes in Create Snapshot Flow for remote store interoperability. ([#7118](https://github.com/opensearch-project/OpenSearch/pull/7118))
 - Allow insecure string settings to warn-log usage and advise to migration of a newer secure variant ([#5496](https://github.com/opensearch-project/OpenSearch/pull/5496))
+- [Search Pipelines] Pass "adhocness" flag to processor factories ([#8164](https://github.com/opensearch-project/OpenSearch/pull/8164))
 
 ### Deprecated
 

modules/search-pipeline-common/src/main/java/org/opensearch/search/pipeline/common/FilterQueryRequestProcessor.java

@@ -13,12 +13,12 @@
 import org.opensearch.common.xcontent.LoggingDeprecationHandler;
 import org.opensearch.common.xcontent.XContentType;
 import org.opensearch.common.xcontent.json.JsonXContent;
-import org.opensearch.core.ParseField;
 import org.opensearch.core.xcontent.NamedXContentRegistry;
 import org.opensearch.core.xcontent.XContentBuilder;
 import org.opensearch.core.xcontent.XContentParser;
 import org.opensearch.index.query.BoolQueryBuilder;
 import org.opensearch.index.query.QueryBuilder;
+import org.opensearch.ingest.ConfigurationUtils;
 import org.opensearch.search.builder.SearchSourceBuilder;
 import org.opensearch.search.pipeline.Processor;
 import org.opensearch.search.pipeline.SearchRequestProcessor;
@@ -89,8 +89,8 @@ public SearchRequest processRequest(SearchRequest request) throws Exception {
     }
 
     static class Factory implements Processor.Factory<SearchRequestProcessor> {
+        private static final String QUERY_KEY = "query";
         private final NamedXContentRegistry namedXContentRegistry;
-        public static final ParseField QUERY_FIELD = new ParseField("query");
 
         Factory(NamedXContentRegistry namedXContentRegistry) {
             this.namedXContentRegistry = namedXContentRegistry;
@@ -103,28 +103,18 @@ public FilterQueryRequestProcessor create(
             String description,
             Map<String, Object> config
         ) throws Exception {
+            Map<String, Object> query = ConfigurationUtils.readOptionalMap(TYPE, tag, config, QUERY_KEY);
+            if (query == null) {
+                throw new IllegalArgumentException("Did not specify the " + QUERY_KEY + " property in processor of type " + TYPE);
+            }
             try (
-                XContentBuilder builder = XContentBuilder.builder(JsonXContent.jsonXContent).map(config);
+                XContentBuilder builder = XContentBuilder.builder(JsonXContent.jsonXContent).map(query);
                 InputStream stream = BytesReference.bytes(builder).streamInput();
                 XContentParser parser = XContentType.JSON.xContent()
                     .createParser(namedXContentRegistry, LoggingDeprecationHandler.INSTANCE, stream)
             ) {
-                XContentParser.Token token = parser.nextToken();
-                assert token == XContentParser.Token.START_OBJECT;
-                String currentFieldName = null;
-                while ((token = parser.nextToken()) != XContentParser.Token.END_OBJECT) {
-                    if (token == XContentParser.Token.FIELD_NAME) {
-                        currentFieldName = parser.currentName();
-                    } else if (token == XContentParser.Token.START_OBJECT) {
-                        if (QUERY_FIELD.match(currentFieldName, parser.getDeprecationHandler())) {
-                            return new FilterQueryRequestProcessor(tag, description, parseInnerQueryBuilder(parser));
-                        }
-                    }
-                }
+                return new FilterQueryRequestProcessor(tag, description, parseInnerQueryBuilder(parser));
             }
-            throw new IllegalArgumentException(
-                "Did not specify the " + QUERY_FIELD.getPreferredName() + " property in processor of type " + TYPE
-            );
         }
     }
 }

modules/search-pipeline-common/src/test/java/org/opensearch/search/pipeline/common/FilterQueryRequestProcessorTests.java

@@ -16,6 +16,7 @@
 import org.opensearch.test.AbstractBuilderTestCase;
 
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.Map;
 
 public class FilterQueryRequestProcessorTests extends AbstractBuilderTestCase {
@@ -37,12 +38,8 @@ public void testFilterQuery() throws Exception {
 
     public void testFactory() throws Exception {
         FilterQueryRequestProcessor.Factory factory = new FilterQueryRequestProcessor.Factory(this.xContentRegistry());
-        FilterQueryRequestProcessor processor = factory.create(
-            Collections.emptyMap(),
-            null,
-            null,
-            Map.of("query", Map.of("term", Map.of("field", "value")))
-        );
+        Map<String, Object> configMap = new HashMap<>(Map.of("query", Map.of("term", Map.of("field", "value"))));
+        FilterQueryRequestProcessor processor = factory.create(Collections.emptyMap(), null, null, configMap);
         assertEquals(new TermQueryBuilder("field", "value"), processor.filterQuery);
 
         // Missing "query" parameter:

server/src/main/java/org/opensearch/search/pipeline/Pipeline.java

@@ -67,19 +67,20 @@ static Pipeline create(
         Map<String, Object> config,
         Map<String, Processor.Factory<SearchRequestProcessor>> requestProcessorFactories,
         Map<String, Processor.Factory<SearchResponseProcessor>> responseProcessorFactories,
-        NamedWriteableRegistry namedWriteableRegistry
+        NamedWriteableRegistry namedWriteableRegistry,
+        boolean isAdHoc
     ) throws Exception {
         String description = ConfigurationUtils.readOptionalStringProperty(null, null, config, DESCRIPTION_KEY);
         Integer version = ConfigurationUtils.readIntProperty(null, null, config, VERSION_KEY, null);
         List<Map<String, Object>> requestProcessorConfigs = ConfigurationUtils.readOptionalList(null, null, config, REQUEST_PROCESSORS_KEY);
-        List<SearchRequestProcessor> requestProcessors = readProcessors(requestProcessorFactories, requestProcessorConfigs);
+        List<SearchRequestProcessor> requestProcessors = readProcessors(requestProcessorFactories, requestProcessorConfigs, isAdHoc);
         List<Map<String, Object>> responseProcessorConfigs = ConfigurationUtils.readOptionalList(
             null,
             null,
             config,
             RESPONSE_PROCESSORS_KEY
         );
-        List<SearchResponseProcessor> responseProcessors = readProcessors(responseProcessorFactories, responseProcessorConfigs);
+        List<SearchResponseProcessor> responseProcessors = readProcessors(responseProcessorFactories, responseProcessorConfigs, isAdHoc);
         if (config.isEmpty() == false) {
             throw new OpenSearchParseException(
                 "pipeline ["
@@ -93,7 +94,8 @@ static Pipeline create(
 
     private static <T extends Processor> List<T> readProcessors(
         Map<String, Processor.Factory<T>> processorFactories,
-        List<Map<String, Object>> requestProcessorConfigs
+        List<Map<String, Object>> requestProcessorConfigs,
+        boolean isAdHoc
     ) throws Exception {
         List<T> processors = new ArrayList<>();
         if (requestProcessorConfigs == null) {
@@ -106,9 +108,25 @@ private static <T extends Processor> List<T> readProcessors(
                     throw new IllegalArgumentException("Invalid processor type " + type);
                 }
                 Map<String, Object> config = (Map<String, Object>) entry.getValue();
+                if (isAdHoc) {
+                    config.put(Processor.AD_HOC_PIPELINE, true);
+                }
                 String tag = ConfigurationUtils.readOptionalStringProperty(null, null, config, TAG_KEY);
                 String description = ConfigurationUtils.readOptionalStringProperty(null, tag, config, DESCRIPTION_KEY);
                 processors.add(processorFactories.get(type).create(processorFactories, tag, description, config));
+                config.remove(Processor.AD_HOC_PIPELINE);
+                if (config.isEmpty() == false) {
+                    String processorName = type;
+                    if (tag != null) {
+                        processorName = processorName + ":" + tag;
+                    }
+                    throw new OpenSearchParseException(
+                        "processor ["
+                            + processorName
+                            + "] doesn't support one or more provided configuration parameters "
+                            + Arrays.toString(config.keySet().toArray())
+                    );
+                }
             }
         }
         return Collections.unmodifiableList(processors);

server/src/main/java/org/opensearch/search/pipeline/Processor.java

@@ -33,6 +33,12 @@
  * @opensearch.internal
  */
 public interface Processor {
+    /**
+     * Processor configuration key to let the factory know that the pipeline is defined in a search request.
+     * For processors whose creation is expensive (e.g. creates a connection pool), the factory can reject
+     * the request or create a more lightweight (but possibly less efficient) version of the processor.
+     */
+    String AD_HOC_PIPELINE = "ad_hoc_pipeline";
 
     /**
      * Gets the type of processor

server/src/main/java/org/opensearch/search/pipeline/SearchPipelineService.java

@@ -177,7 +177,8 @@ void innerUpdatePipelines(SearchPipelineMetadata newSearchPipelineMetadata) {
                     newConfiguration.getConfigAsMap(),
                     requestProcessorFactories,
                     responseProcessorFactories,
-                    namedWriteableRegistry
+                    namedWriteableRegistry,
+                    false
                 );
                 newPipelines.put(newConfiguration.getId(), new PipelineHolder(newConfiguration, newPipeline));
 
@@ -276,7 +277,8 @@ void validatePipeline(Map<DiscoveryNode, SearchPipelineInfo> searchPipelineInfos
             pipelineConfig,
             requestProcessorFactories,
             responseProcessorFactories,
-            namedWriteableRegistry
+            namedWriteableRegistry,
+            false
         );
         List<Exception> exceptions = new ArrayList<>();
         for (SearchRequestProcessor processor : pipeline.getSearchRequestProcessors()) {
@@ -372,7 +374,8 @@ public PipelinedRequest resolvePipeline(SearchRequest searchRequest) throws Exce
                     searchRequest.source().searchPipelineSource(),
                     requestProcessorFactories,
                     responseProcessorFactories,
-                    namedWriteableRegistry
+                    namedWriteableRegistry,
+                    true
                 );
             } catch (Exception e) {
                 throw new SearchPipelineProcessingException(e);

server/src/test/java/org/opensearch/search/pipeline/SearchPipelineServiceTests.java

@@ -35,6 +35,7 @@
 import org.opensearch.common.xcontent.XContentType;
 import org.opensearch.index.IndexSettings;
 import org.opensearch.index.query.TermQueryBuilder;
+import org.opensearch.ingest.ConfigurationUtils;
 import org.opensearch.plugins.SearchPipelinePlugin;
 import org.opensearch.search.SearchHit;
 import org.opensearch.search.SearchHits;
@@ -786,4 +787,38 @@ public void testExceptionOnResponseProcessing() throws Exception {
         // Exception thrown when processing response
         expectThrows(SearchPipelineProcessingException.class, () -> pipelinedRequest.transformResponse(response));
     }
+
+    public void testAdHocRejectingProcessor() {
+        String processorType = "ad_hoc_rejecting";
+        Map<String, Processor.Factory<SearchRequestProcessor>> requestProcessorFactories = Map.of(processorType, (pf, t, d, c) -> {
+            if (ConfigurationUtils.readBooleanProperty(processorType, t, c, Processor.AD_HOC_PIPELINE, false)) {
+                throw new IllegalArgumentException(processorType + " cannot be created as part of a pipeline defined in a search request");
+            }
+            return new FakeRequestProcessor(processorType, t, d, r -> {});
+        });
+
+        SearchPipelineService searchPipelineService = createWithProcessors(requestProcessorFactories, Collections.emptyMap());
+
+        String id = "_id";
+        SearchPipelineService.PipelineHolder pipeline = searchPipelineService.getPipelines().get(id);
+        assertNull(pipeline);
+        ClusterState clusterState = ClusterState.builder(new ClusterName("_name")).build();
+        PutSearchPipelineRequest putRequest = new PutSearchPipelineRequest(
+            id,
+            new BytesArray("{\"request_processors\":[" + " { \"" + processorType + "\": {}}" + "]}"),
+            XContentType.JSON
+        );
+        ClusterState previousClusterState = clusterState;
+        clusterState = SearchPipelineService.innerPut(putRequest, clusterState);
+        // The following line successfully creates the pipeline:
+        searchPipelineService.applyClusterState(new ClusterChangedEvent("", clusterState, previousClusterState));
+
+        Map<String, Object> pipelineSourceMap = new HashMap<>();
+        pipelineSourceMap.put(Pipeline.REQUEST_PROCESSORS_KEY, List.of(Map.of(processorType, Collections.emptyMap())));
+
+        SearchSourceBuilder sourceBuilder = SearchSourceBuilder.searchSource().searchPipelineSource(pipelineSourceMap);
+        SearchRequest searchRequest = new SearchRequest().source(sourceBuilder);
+        expectThrows(SearchPipelineProcessingException.class, () -> searchPipelineService.resolvePipeline(searchRequest));
+
+    }
 }