NIFI-15477 Added recordGauge method to ProcessSession

This closes #49.

Signed-off-by: Pierre Villard <[email protected]>

Author: exceptionfactory

src/main/java/org/apache/nifi/processor/ProcessSession.java

@@ -37,6 +37,7 @@
 import org.apache.nifi.processor.io.InputStreamCallback;
 import org.apache.nifi.processor.io.OutputStreamCallback;
 import org.apache.nifi.processor.io.StreamCallback;
+import org.apache.nifi.processor.metrics.CommitTiming;
 import org.apache.nifi.provenance.ProvenanceReporter;
 import org.apache.nifi.provenance.ProvenanceEventType;
 
@@ -253,6 +254,18 @@ default void commitAsync(Runnable onSuccess) {
      */
     void adjustCounter(String name, long delta, boolean immediate);
 
+    /**
+     * Record measurement value for the named Gauge, registering the named Gauge when not present in the system.
+     * Gauges represent a measurement at a point in time, unlike counters that track cumulative values.
+     *
+     * @param name Gauge name to update or register
+     * @param value Measurement value to record
+     * @param commitTiming Timing for when the measurement value should be committed
+     */
+    default void recordGauge(String name, double value, CommitTiming commitTiming) {
+
+    }
+
     /**
      * Returns the {@link FlowFile} from the work queue that is next highest priority to process.
      * If no FlowFiles are available, returns {@code null}.

src/main/java/org/apache/nifi/processor/metrics/CommitTiming.java

@@ -0,0 +1,28 @@
+/*
+ * 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.processor.metrics;
+
+/**
+ * Enumeration of timing options for committing metrics
+ */
+public enum CommitTiming {
+    /** Commit metrics immediately regardless of session transaction status */
+    NOW,
+
+    /** Commit metrics on successful commit of session transaction */
+    SESSION_COMMITTED
+}