NicoK commented on a change in pull request #8887: [FLINK-12982][metrics]
improve DescriptiveStatisticsHistogramStatistics performance
URL: https://github.com/apache/flink/pull/8887#discussion_r314405857
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File path:
flink-runtime/src/main/java/org/apache/flink/runtime/metrics/DescriptiveStatisticsHistogramStatistics.java
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@@ -19,53 +19,174 @@
import org.apache.flink.metrics.HistogramStatistics;
+import org.apache.commons.math3.exception.MathIllegalArgumentException;
import org.apache.commons.math3.stat.descriptive.DescriptiveStatistics;
+import org.apache.commons.math3.stat.descriptive.UnivariateStatistic;
+import org.apache.commons.math3.stat.descriptive.moment.SecondMoment;
+import org.apache.commons.math3.stat.descriptive.moment.StandardDeviation;
+import org.apache.commons.math3.stat.descriptive.rank.Percentile;
+import org.apache.commons.math3.stat.ranking.NaNStrategy;
import java.util.Arrays;
/**
* DescriptiveStatistics histogram statistics implementation returned by
{@link DescriptiveStatisticsHistogram}.
- * The statistics class wraps a {@link DescriptiveStatistics} instance and
forwards the method calls accordingly.
+ *
+ * <p>The statistics takes a point-in-time snapshot of a {@link
DescriptiveStatistics} instance and
+ * allows optimised metrics retrieval from this.
*/
public class DescriptiveStatisticsHistogramStatistics extends
HistogramStatistics {
- private final DescriptiveStatistics descriptiveStatistics;
+ private final CommonMetricsSnapshot statisticsSummary = new
CommonMetricsSnapshot();
public DescriptiveStatisticsHistogramStatistics(DescriptiveStatistics
latencyHistogram) {
- this.descriptiveStatistics = latencyHistogram;
+ latencyHistogram.apply(statisticsSummary);
}
@Override
public double getQuantile(double quantile) {
- return descriptiveStatistics.getPercentile(quantile * 100);
+ return statisticsSummary.getPercentile(quantile * 100);
}
@Override
public long[] getValues() {
- return
Arrays.stream(descriptiveStatistics.getValues()).mapToLong(i -> (long)
i).toArray();
+ return Arrays.stream(statisticsSummary.getValues()).mapToLong(i
-> (long) i).toArray();
}
@Override
public int size() {
- return (int) descriptiveStatistics.getN();
+ return (int) statisticsSummary.getCount();
}
@Override
public double getMean() {
- return descriptiveStatistics.getMean();
+ return statisticsSummary.getMean();
}
@Override
public double getStdDev() {
- return descriptiveStatistics.getStandardDeviation();
+ return statisticsSummary.getStandardDeviation();
}
@Override
public long getMax() {
- return (long) descriptiveStatistics.getMax();
+ return (long) statisticsSummary.getMax();
}
@Override
public long getMin() {
- return (long) descriptiveStatistics.getMin();
+ return (long) statisticsSummary.getMin();
+ }
+
+ /**
+ * Function to extract several commonly used metrics in an optimised
way, i.e. with as few runs
+ * over the data / calculations as possible.
+ *
+ * <p>Note that calls to {@link #evaluate(double[])} or {@link
#evaluate(double[], int, int)}
+ * will not return a value but instead populate this class so that
further values can be
+ * retrieved from it.
+ */
+ private static class CommonMetricsSnapshot implements
UnivariateStatistic {
+ long count = 0;
+ double min = Double.NaN;
+ double max = Double.NaN;
+ double mean = Double.NaN;
+ double stddev = Double.NaN;
+ private Percentile percentilesImpl = new
Percentile().withNaNStrategy(NaNStrategy.FIXED);
Review comment:
cannot be due to the `copy()` method
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