Github user markap14 commented on a diff in the pull request:
https://github.com/apache/nifi/pull/2130#discussion_r137855135
--- Diff:
nifi-nar-bundles/nifi-standard-services/nifi-lookup-services-bundle/nifi-lookup-services/src/main/java/org/apache/nifi/lookup/CSVRecordLookupService.java
---
@@ -0,0 +1,232 @@
+/*
+ * 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.lookup;
+
+import org.apache.commons.csv.CSVFormat;
+import org.apache.commons.csv.CSVParser;
+import org.apache.commons.csv.CSVRecord;
+import org.apache.commons.lang3.StringUtils;
+import org.apache.nifi.annotation.documentation.CapabilityDescription;
+import org.apache.nifi.annotation.documentation.Tags;
+import org.apache.nifi.annotation.lifecycle.OnEnabled;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.controller.AbstractControllerService;
+import org.apache.nifi.controller.ConfigurationContext;
+import org.apache.nifi.controller.ControllerServiceInitializationContext;
+import org.apache.nifi.logging.ComponentLog;
+import org.apache.nifi.processor.util.StandardValidators;
+import org.apache.nifi.reporting.InitializationException;
+import org.apache.nifi.serialization.SimpleRecordSchema;
+import org.apache.nifi.serialization.record.MapRecord;
+import org.apache.nifi.serialization.record.Record;
+import org.apache.nifi.serialization.record.RecordField;
+import org.apache.nifi.serialization.record.RecordFieldType;
+import org.apache.nifi.serialization.record.RecordSchema;
+import org.apache.nifi.util.file.monitor.LastModifiedMonitor;
+import org.apache.nifi.util.file.monitor.SynchronousFileWatcher;
+
+import java.io.FileNotFoundException;
+import java.io.FileReader;
+import java.io.IOException;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+@Tags({"lookup", "cache", "enrich", "join", "csv", "reloadable", "key",
"value", "record"})
+@CapabilityDescription("A reloadable CSV file-based lookup service. When
the lookup key is found in the CSV file, the remaining columns are returned as
a Record.")
--- End diff --
We also need to make sure that we document that the coordinates passed to
the lookup must contain the key 'key' and that this is how the lookup is
performed. If a user has a CSV file with 3 columns, "id", "name", and
"description" for instance, I imagine that some users will be tempted to
perform a lookup using coordinates "id" = "3" instead of "key" = "3".
Alternatively, you could also consider making the coordinates use the 'Lookup
Key Column' instead of the string "key". For instance, if the "Lookup Key
Column" is set to "id" then require that the "id" coordinate be passed in. I
think either approach is reasonable but needs to be documented.
---
