add double summary gauge to track statistics directly

nb-api/src/main/java/io/nosqlbench/api/engine/metrics/ActivityMetrics.java

@@ -29,6 +29,7 @@ import org.apache.logging.log4j.Logger;
 import java.io.File;
 import java.io.PrintStream;
 import java.util.ArrayList;
+import java.util.DoubleSummaryStatistics;
 import java.util.List;
 import java.util.ServiceLoader;
 import java.util.concurrent.TimeUnit;
@@ -189,11 +190,32 @@ public class ActivityMetrics {
         return registry;
     }
 
+    /**
+     * This variant creates a named metric for all of the stats which may be needed, name with metricname_average,
+     * and so on. It uses the same data reservoir for all views, but only returns one of them as a handle to the metric.
+     * This has the effect of leaving some of the metric objects unreferencable from the caller side. This may need
+     * to be changed in a future update in the even that full inventory management is required on metric objects here.
+     * @param parent The labeled element the metric pertains to
+     * @param metricFamilyName The name of the measurement
+     * @return One of the created metrics, suitable for calling {@link DoubleSummaryGauge#accept(double)} on.
+     */
+    public static DoubleSummaryGauge summaryGauge(NBLabeledElement parent, String metricFamilyName) {
+        DoubleSummaryStatistics stats = new DoubleSummaryStatistics();
+        DoubleSummaryGauge anyGauge = null;
+        for (DoubleSummaryGauge.Stat statName: DoubleSummaryGauge.Stat.values()){
+            final NBLabels labels = parent.getLabels()
+                .andTypes("name",sanitize(metricFamilyName))
+                .modifyValue("name", n -> n+"_"+statName.name().toLowerCase());
+            anyGauge= (DoubleSummaryGauge) register(labels, () -> new DoubleSummaryGauge(labels,statName,stats));
+        }
+        return anyGauge;
+    }
+
     @SuppressWarnings("unchecked")
     public static <T> Gauge<T> gauge(NBLabeledElement parent, String metricFamilyName, Gauge<T> gauge) {
         final NBLabels labels = parent.getLabels().andTypes("name",sanitize(metricFamilyName));
 
-        return (Gauge<T>) register(labels, () -> new NBMetricGauge(labels,gauge));
+        return (Gauge<T>) register(labels, () -> new NBMetricGaugeWrapper<>(labels,gauge));
     }
 
     private static MetricRegistry lookupRegistry() {

nb-api/src/main/java/io/nosqlbench/api/engine/metrics/DoubleSummaryGauge.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2023 nosqlbench
+ *
+ * Licensed 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 io.nosqlbench.api.engine.metrics;
+
+import io.nosqlbench.api.config.NBLabels;
+import io.nosqlbench.api.engine.metrics.instruments.NBMetricGauge;
+
+import java.util.DoubleSummaryStatistics;
+
+
+/**
+ * Create a discrete stat reservoir as a gauge.
+ */
+public class DoubleSummaryGauge implements NBMetricGauge<Double> {
+    private final NBLabels labels;
+    private final Stat stat;
+    private final DoubleSummaryStatistics stats;
+
+    public enum Stat {
+        Min,
+        Max,
+        Average,
+        Count,
+        Sum
+    }
+
+    public DoubleSummaryGauge(NBLabels labels, Stat stat, DoubleSummaryStatistics stats) {
+        this.labels = labels;
+        this.stat = stat;
+        this.stats = stats;
+    }
+
+    public DoubleSummaryGauge(NBLabels labels, Stat stat) {
+        this.labels = labels;
+        this.stat = stat;
+        this.stats = new DoubleSummaryStatistics();
+    }
+
+    public synchronized void accept(double value) {
+        stats.accept(value);
+    }
+    @Override
+    public synchronized Double getValue() {
+        return switch(stat) {
+            case Min -> stats.getMin();
+            case Max -> stats.getMax();
+            case Average -> stats.getAverage();
+            case Count -> (double) stats.getCount();
+            case Sum -> stats.getSum();
+        };
+    }
+
+    @Override
+    public NBLabels getLabels() {
+        return labels;
+    }
+
+}

nb-api/src/main/java/io/nosqlbench/api/engine/metrics/instruments/NBMetricGauge.java

@@ -18,25 +18,7 @@ package io.nosqlbench.api.engine.metrics.instruments;
 
 import com.codahale.metrics.Gauge;
 import io.nosqlbench.api.config.NBLabeledElement;
-import io.nosqlbench.api.config.NBLabels;
 
-public class NBMetricGauge<T> implements Gauge<T>, NBLabeledElement {
+public interface NBMetricGauge<T> extends Gauge<T>, NBLabeledElement {
 
-    private final Gauge<? extends T> gauge;
-    private final NBLabels labels;
-
-    public NBMetricGauge(NBLabels labels, Gauge<? extends T> gauge) {
-        this.gauge = gauge;
-        this.labels = labels;
-    }
-
-    @Override
-    public T getValue() {
-        return gauge.getValue();
-    }
-
-    @Override
-    public NBLabels getLabels() {
-        return labels;
-    }
 }

nb-api/src/main/java/io/nosqlbench/api/engine/metrics/instruments/NBMetricGaugeWrapper.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2023 nosqlbench
+ *
+ * Licensed 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 io.nosqlbench.api.engine.metrics.instruments;
+
+import com.codahale.metrics.Gauge;
+import io.nosqlbench.api.config.NBLabels;
+
+public class NBMetricGaugeWrapper<T> implements NBMetricGauge<T> {
+
+    private final Gauge<? extends T> gauge;
+    private final NBLabels labels;
+
+    public NBMetricGaugeWrapper(NBLabels labels, Gauge<? extends T> gauge) {
+        this.gauge = gauge;
+        this.labels = labels;
+    }
+
+    @Override
+    public T getValue() {
+        return gauge.getValue();
+    }
+
+    @Override
+    public NBLabels getLabels() {
+        return labels;
+    }
+}