ChrisSamo632 commented on a change in pull request #5193:
URL: https://github.com/apache/nifi/pull/5193#discussion_r676480488



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File path: 
nifi-nar-bundles/nifi-elasticsearch-bundle/nifi-elasticsearch-restapi-processors/src/main/java/org/apache/nifi/processors/elasticsearch/AbstractJsonQueryElasticsearch.java
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@@ -0,0 +1,293 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.nifi.processors.elasticsearch;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.apache.nifi.annotation.lifecycle.OnScheduled;
+import org.apache.nifi.annotation.lifecycle.OnStopped;
+import org.apache.nifi.components.AllowableValue;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.elasticsearch.ElasticSearchClientService;
+import org.apache.nifi.elasticsearch.SearchResponse;
+import org.apache.nifi.expression.ExpressionLanguageScope;
+import org.apache.nifi.flowfile.FlowFile;
+import org.apache.nifi.flowfile.attributes.CoreAttributes;
+import org.apache.nifi.processor.AbstractProcessor;
+import org.apache.nifi.processor.ProcessContext;
+import org.apache.nifi.processor.ProcessSession;
+import org.apache.nifi.processor.Relationship;
+import org.apache.nifi.processors.elasticsearch.api.JsonQueryParameters;
+import org.apache.nifi.util.StopWatch;
+import org.apache.nifi.util.StringUtils;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicReference;
+
+public abstract class AbstractJsonQueryElasticsearch<Q extends 
JsonQueryParameters> extends AbstractProcessor implements 
ElasticsearchRestProcessor {
+    public static final Relationship REL_ORIGINAL = new 
Relationship.Builder().name("original")
+            .description("All original flowfiles that don't cause an error to 
occur go to this relationship.").build();
+    public static final Relationship REL_HITS = new 
Relationship.Builder().name("hits")
+            .description("Search hits are routed to this relationship.")
+            .build();
+    public static final Relationship REL_AGGREGATIONS = new 
Relationship.Builder().name("aggregations")
+            .description("Aggregations are routed to this relationship.")
+            .build();
+
+    public static final AllowableValue SPLIT_UP_YES = new AllowableValue(
+            "splitUp-yes",
+            "Yes",
+            "Split up results."
+    );
+    public static final AllowableValue SPLIT_UP_NO = new AllowableValue(
+            "splitUp-no",
+            "No",
+            "Don't split up results."
+    );
+
+    public static final PropertyDescriptor SPLIT_UP_HITS = new 
PropertyDescriptor.Builder()
+            .name("el-rest-split-up-hits")
+            .displayName("Split up search results")
+            .description("Split up search results into one flowfile per 
result.")
+            .allowableValues(SPLIT_UP_NO, SPLIT_UP_YES)
+            .defaultValue(SPLIT_UP_NO.getValue())
+            .required(true)
+            .expressionLanguageSupported(ExpressionLanguageScope.NONE)
+            .build();
+    public static final PropertyDescriptor SPLIT_UP_AGGREGATIONS = new 
PropertyDescriptor.Builder()
+            .name("el-rest-split-up-aggregations")
+            .displayName("Split up aggregation results")
+            .description("Split up aggregation results into one flowfile per 
result.")
+            .allowableValues(SPLIT_UP_NO, SPLIT_UP_YES)
+            .defaultValue(SPLIT_UP_NO.getValue())
+            .required(true)
+            .expressionLanguageSupported(ExpressionLanguageScope.NONE)
+            .build();
+
+    private static final Set<Relationship> relationships;
+    private static final List<PropertyDescriptor> propertyDescriptors;
+
+    AtomicReference<ElasticSearchClientService> clientService;
+    String splitUpHits;
+    private String splitUpAggregations;
+
+    final ObjectMapper mapper = new ObjectMapper();
+
+    static {
+        final Set<Relationship> rels = new HashSet<>();
+        rels.add(REL_ORIGINAL);
+        rels.add(REL_FAILURE);
+        rels.add(REL_HITS);
+        rels.add(REL_AGGREGATIONS);
+        relationships = Collections.unmodifiableSet(rels);
+
+        final List<PropertyDescriptor> descriptors = new ArrayList<>();
+        descriptors.add(QUERY);
+        descriptors.add(QUERY_ATTRIBUTE);
+        descriptors.add(INDEX);
+        descriptors.add(TYPE);
+        descriptors.add(CLIENT_SERVICE);
+        descriptors.add(SPLIT_UP_HITS);
+        descriptors.add(SPLIT_UP_AGGREGATIONS);
+
+        propertyDescriptors = Collections.unmodifiableList(descriptors);
+    }
+
+    @Override
+    public Set<Relationship> getRelationships() {
+        return relationships;
+    }
+
+    @Override
+    public List<PropertyDescriptor> getSupportedPropertyDescriptors() {
+        return propertyDescriptors;
+    }
+
+    @OnScheduled
+    public void onScheduled(final ProcessContext context) {
+        clientService = new 
AtomicReference<>(context.getProperty(CLIENT_SERVICE).asControllerService(ElasticSearchClientService.class));
+
+        splitUpHits = context.getProperty(SPLIT_UP_HITS).getValue();
+        splitUpAggregations = 
context.getProperty(SPLIT_UP_AGGREGATIONS).getValue();
+    }
+
+    @OnStopped
+    public void onStopped() {
+        this.clientService = null;
+    }
+
+    @Override
+    public void onTrigger(final ProcessContext context, final ProcessSession 
session) {
+        FlowFile input = null;
+        if (context.hasIncomingConnection()) {
+            input = session.get();
+
+            if (input == null && context.hasNonLoopConnection()) {
+                return;
+            }
+        }
+
+        try {
+            final Q queryJsonParameters = buildJsonQueryParameters(input, 
context, session);
+
+            List<FlowFile> hitsFlowFiles = new ArrayList<>();
+            final StopWatch stopWatch = new StopWatch(true);
+            final SearchResponse response = doQuery(queryJsonParameters, 
hitsFlowFiles, session, input, stopWatch);
+
+            finishQuery(input, queryJsonParameters, session, response);
+        } catch (Exception ex) {
+            getLogger().error("Error processing flowfile.", ex);
+            if (input != null) {
+                session.transfer(input, REL_FAILURE);
+            }
+            context.yield();
+        }
+    }
+
+    abstract Q buildJsonQueryParameters(final FlowFile input, final 
ProcessContext context, final ProcessSession session) throws IOException;
+
+    void populateCommonJsonQueryParameters(final Q queryJsonParameters, final 
FlowFile input, final ProcessContext context,
+                                           final ProcessSession session) 
throws IOException {
+        final String query = getQuery(input, context, session);
+        final String index = 
context.getProperty(INDEX).evaluateAttributeExpressions(input).getValue();
+        final String type = 
context.getProperty(TYPE).evaluateAttributeExpressions(input).getValue();
+        final String queryAttr = context.getProperty(QUERY_ATTRIBUTE).isSet()
+                ? 
context.getProperty(QUERY_ATTRIBUTE).evaluateAttributeExpressions(input).getValue()
+                : null;
+
+        queryJsonParameters.setQuery(query);
+        queryJsonParameters.setIndex(index);
+        queryJsonParameters.setType(type);
+        queryJsonParameters.setQueryAttr(queryAttr);
+    }
+
+    abstract SearchResponse doQuery(final Q queryJsonParameters, final 
List<FlowFile> hitsFlowFiles, final ProcessSession session,
+                                    final FlowFile input, final StopWatch 
stopWatch) throws IOException;
+
+    abstract void finishQuery(final FlowFile input, final Q queryParameters, 
final ProcessSession session,
+                              final SearchResponse response) throws 
IOException;
+
+    FlowFile createChildFlowFile(final ProcessSession session, final FlowFile 
parent) {
+        return parent != null ? session.create(parent) : session.create();
+    }
+
+    private FlowFile writeAggregationFlowFileContents(final String name, final 
Integer number, final String json,
+                                                      final ProcessSession 
session, final FlowFile aggFlowFile,
+                                                      final Map<String, 
String> attributes) {
+        FlowFile ff = session.write(aggFlowFile, out -> 
out.write(json.getBytes()));
+        ff = session.putAllAttributes(ff, new HashMap<String, String>(){{
+            if (name != null) {
+                put("aggregation.name", name);
+            }
+            if (number != null) {
+                put("aggregation.number", number.toString());
+            }
+        }});
+
+        return session.putAllAttributes(ff, attributes);
+    }
+
+    private void handleAggregations(final Map<String, Object> aggregations, 
final ProcessSession session,
+                                    final FlowFile parent, final Map<String, 
String> attributes,
+                                    final String transitUri, final StopWatch 
stopWatch) throws IOException {
+        if (aggregations != null && !aggregations.isEmpty()) {
+            final List<FlowFile> aggsFlowFiles = new ArrayList<>();
+            if (splitUpAggregations.equals(SPLIT_UP_YES.getValue())) {
+                int aggCount = 0;
+                for (final Map.Entry<String, Object> agg : 
aggregations.entrySet()) {
+                    final FlowFile aggFlowFile = createChildFlowFile(session, 
parent);
+                    final String aggJson = 
mapper.writeValueAsString(agg.getValue());
+                    
aggsFlowFiles.add(writeAggregationFlowFileContents(agg.getKey(), ++aggCount, 
aggJson, session, aggFlowFile, attributes));
+                }
+            } else {
+                final FlowFile aggFlowFile = createChildFlowFile(session, 
parent);
+                final String json = mapper.writeValueAsString(aggregations);
+                aggsFlowFiles.add(writeAggregationFlowFileContents(null, null, 
json, session, aggFlowFile, attributes));
+            }
+
+            if (!aggsFlowFiles.isEmpty()) {
+                session.transfer(aggsFlowFiles, REL_AGGREGATIONS);
+                aggsFlowFiles.forEach(ff -> 
session.getProvenanceReporter().receive(ff, transitUri, 
stopWatch.getElapsed(TimeUnit.MILLISECONDS)));
+            }
+        }
+    }
+
+    private FlowFile writeHitFlowFile(final int count, final String json, 
final ProcessSession session,
+                                      final FlowFile hitFlowFile, final 
Map<String, String> attributes) {
+        final FlowFile ff = session.write(hitFlowFile, out -> 
out.write(json.getBytes()));
+        attributes.put("hit.count", Integer.toString(count));
+
+        return session.putAllAttributes(ff, attributes);
+    }
+
+    List<FlowFile> handleHits(final List<Map<String, Object>> hits, final Q 
queryJsonParameters, final ProcessSession session,
+                              final FlowFile parent, final Map<String, String> 
attributes, final List<FlowFile> hitsFlowFiles,
+                              final String transitUri, final StopWatch 
stopWatch) throws IOException {
+        if (hits != null && !hits.isEmpty()) {
+            if (SPLIT_UP_YES.getValue().equals(splitUpHits)) {
+                for (final Map<String, Object> hit : hits) {
+                    final FlowFile hitFlowFile = createChildFlowFile(session, 
parent);
+                    final String json = mapper.writeValueAsString(hit);
+                    hitsFlowFiles.add(writeHitFlowFile(1, json, session, 
hitFlowFile, attributes));
+                }
+            } else {
+                final FlowFile hitFlowFile = createChildFlowFile(session, 
parent);
+                final String json = mapper.writeValueAsString(hits);
+                hitsFlowFiles.add(writeHitFlowFile(hits.size(), json, session, 
hitFlowFile, attributes));
+            }
+        }
+
+        // output any results
+        if (!hitsFlowFiles.isEmpty()) {

Review comment:
       It will always be empty for processing non-combined results of paginated 
queries.
   
   It's used for combining the hits between pages of results with the 
`List<FlowFile>` being returned by `handleHits` => `handleResponse` => 
`doQuery` to be sent back through that chain on the next iteration through 
`doQuery` so that the existing `FlowFile` can be reused to append new hits into.
   
   I agree this is a little confusing when reading the 
`AbstractJsonQueryElasticsearch#handleHits` method code on its own - maybe some 
comments here would be useful? Could alternatively consider refactoring the 
method into separate methods for the `combined` vs. `non-combined` result 
handling and not return anything for those cases - I'm not sure how much 
complexity that might add (or aleviate) as the whole chain of method calls will 
be impacted, so will give it a quick try and then resort to some comments 
otherwise




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