ENH: Add ProfileLocation - Part 2 - performance metrics for transactions with label and profileLocation

src/main/java/io/ebeaninternal/server/profile/DTimedMetric.java

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+package io.ebeaninternal.server.profile;
+
+import io.ebean.meta.MetaTimedMetric;
+import io.ebeaninternal.metric.TimedMetric;
+
+import java.util.List;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.atomic.LongAccumulator;
+import java.util.concurrent.atomic.LongAdder;
+
+/**
+ * Used to collect timed execution statistics.
+ * <p>
+ * It is intended for high concurrent updates to the statistics and relatively infrequent reads.
+ * </p>
+ */
+class DTimedMetric implements TimedMetric {
+
+  protected final String name;
+
+  protected final LongAdder count = new LongAdder();
+
+  protected final LongAdder total = new LongAdder();
+
+  protected final LongAccumulator max = new LongAccumulator(Math::max, Long.MIN_VALUE);
+
+  protected final AtomicLong startTime = new AtomicLong(System.currentTimeMillis());
+
+  DTimedMetric(String name) {
+    this.name = name;
+  }
+
+  /**
+   * Add a value. Usually the value is Time or Bytes etc.
+   */
+  @Override
+  public void add(long value) {
+
+    count.increment();
+    total.add(value);
+    max.accumulate(value);
+  }
+
+  @Override
+  public boolean isEmpty() {
+    return count.sum() == 0;
+  }
+
+  @Override
+  public void collect(boolean reset, List<MetaTimedMetric> result) {
+    DTimeMetricStats metric = collect(reset);
+    if (metric != null) {
+      result.add(metric);
+    }
+  }
+
+//  @Override
+  public DTimeMetricStats collect(boolean reset) {
+    boolean empty = count.sum() == 0;
+    if (empty) {
+      if (reset) {
+        startTime.set(System.currentTimeMillis());
+      }
+      return null;
+    } else {
+      return getStatistics(reset);
+    }
+  }
+
+  /**
+   * Return the current statistics resetting the internal values if reset is true.
+   */
+  public DTimeMetricStats getStatistics(boolean reset) {
+
+    if (reset) {
+      // Note these values are not guaranteed to be consistent wrt each other
+      // but should be reasonably consistent (small time between count and total)
+      final long maxVal = max.getThenReset();
+      final long totalVal = total.sumThenReset();
+      final long countVal = count.sumThenReset();
+      final long startTimeVal = startTime.getAndSet(System.currentTimeMillis());
+      return new DTimeMetricStats(name, startTimeVal, countVal, totalVal, maxVal);
+
+    } else {
+      return new DTimeMetricStats(name, startTime.get(), count.sum(), total.sum(), max.get());
+    }
+  }
+
+  /**
+   * Reset all the internal counters and start time.
+   */
+  public void reset() {
+    startTime.set(System.currentTimeMillis());
+    max.reset();
+    count.reset();
+    total.reset();
+  }
+
+  /**
+   * Return the start time.
+   */
+  public long getStartTime() {
+    return startTime.get();
+  }
+
+  /**
+   * Return the count of values.
+   */
+  public long getCount() {
+    return count.sum();
+  }
+
+  /**
+   * Return the total of values.
+   */
+  public long getTotal() {
+    return total.sum();
+  }
+
+  /**
+   * Return the max value.
+   */
+  public long getMax() {
+    return max.get();
+  }
+
+}