Github user bbende commented on a diff in the pull request: https://github.com/apache/nifi/pull/2639#discussion_r194424610 --- Diff: nifi-nar-bundles/nifi-hadoop-bundle/nifi-hdfs-processors/src/main/java/org/apache/nifi/processors/hadoop/GetHDFSFileInfo.java --- @@ -0,0 +1,803 @@ +/* + * 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.hadoop; + +import java.io.IOException; +import java.security.PrivilegedExceptionAction; +import java.util.ArrayList; +import java.util.Collection; +import java.util.HashMap; +import java.util.HashSet; +import java.util.LinkedList; +import java.util.List; +import java.util.Map; +import java.util.Set; +import java.util.concurrent.TimeUnit; +import java.util.regex.Pattern; + +import org.apache.commons.lang3.StringUtils; +import org.apache.hadoop.fs.FileStatus; +import org.apache.hadoop.fs.FileSystem; +import org.apache.hadoop.fs.Path; +import org.apache.hadoop.fs.permission.FsAction; +import org.apache.hadoop.fs.permission.FsPermission; +import org.apache.hadoop.security.UserGroupInformation; +import org.apache.nifi.annotation.behavior.InputRequirement; +import org.apache.nifi.annotation.behavior.InputRequirement.Requirement; +import org.apache.nifi.annotation.behavior.TriggerSerially; +import org.apache.nifi.annotation.behavior.TriggerWhenEmpty; +import org.apache.nifi.annotation.behavior.WritesAttribute; +import org.apache.nifi.annotation.behavior.WritesAttributes; +import org.apache.nifi.annotation.documentation.CapabilityDescription; +import org.apache.nifi.annotation.documentation.SeeAlso; +import org.apache.nifi.annotation.documentation.Tags; +import org.apache.nifi.components.AllowableValue; +import org.apache.nifi.components.PropertyDescriptor; +import org.apache.nifi.components.PropertyValue; +import org.apache.nifi.components.ValidationContext; +import org.apache.nifi.components.ValidationResult; +import org.apache.nifi.expression.ExpressionLanguageScope; +import org.apache.nifi.flowfile.FlowFile; +import org.apache.nifi.processor.ProcessContext; +import org.apache.nifi.processor.ProcessSession; +import org.apache.nifi.processor.ProcessorInitializationContext; +import org.apache.nifi.processor.Relationship; +import org.apache.nifi.processor.exception.ProcessException; +import org.apache.nifi.processor.util.StandardValidators; +import org.apache.nifi.processors.hadoop.GetHDFSFileInfo.HDFSFileInfoRequest.Groupping; + +@TriggerSerially +@TriggerWhenEmpty --- End diff -- @TriggerWhenEmpty is used to make the framework trigger the processor when there is an empty incoming connection, is that necessary in this case? You typically use this if there is a case where you need to perform some kind of check/clean-up even when no flow files are available.
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