Github user pvillard31 commented on a diff in the pull request:
https://github.com/apache/nifi/pull/1328#discussion_r95009109
--- Diff:
nifi-nar-bundles/nifi-stateful-analysis-bundle/nifi-stateful-analysis-processors/src/main/java/org/apache/nifi/processors/stateful/analysis/AttributeRollingWindow.java
---
@@ -0,0 +1,325 @@
+/*
+ * 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.stateful.analysis;
+
+import org.apache.nifi.annotation.behavior.InputRequirement;
+import org.apache.nifi.annotation.behavior.Stateful;
+import org.apache.nifi.annotation.behavior.TriggerSerially;
+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.Tags;
+import org.apache.nifi.annotation.lifecycle.OnScheduled;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.components.state.Scope;
+import org.apache.nifi.components.state.StateManager;
+import org.apache.nifi.components.state.StateMap;
+import org.apache.nifi.flowfile.FlowFile;
+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.processor.exception.ProcessException;
+import org.apache.nifi.processor.util.StandardValidators;
+
+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 static
org.apache.nifi.processors.stateful.analysis.AttributeRollingWindow.ROLLING_WINDOW_COUNT_KEY;
+import static
org.apache.nifi.processors.stateful.analysis.AttributeRollingWindow.ROLLING_WINDOW_VALUE_KEY;
+
+@TriggerSerially
+@InputRequirement(InputRequirement.Requirement.INPUT_REQUIRED)
+@Tags({"Attribute Expression Language", "state", "data science",
"rolling", "window"})
+@CapabilityDescription("Track a Rolling Window based on evaluating an
Expression Language expression on each FlowFile and add that value to the
processor's state. Each FlowFile will be emitted " +
+ "with the count of FlowFiles and total aggregate value of values
processed in the current time window.")
+@WritesAttributes({
+ @WritesAttribute(attribute = ROLLING_WINDOW_VALUE_KEY, description
= "The rolling window value (sum of all the values stored)."),
+ @WritesAttribute(attribute = ROLLING_WINDOW_COUNT_KEY, description
= "The count of the number of FlowFiles seen in the rolling window.")
--- End diff --
I know this would be a really easy UpdateAttribute step to add... but could
we also write another attribute containing the mean? I believe this could be
useful to ensure some kind of data quality and check that some data is staying
within a given range.
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