[GitHub] [flink] zentol commented on a change in pull request #14340: [FLINK-20533][datadog] Add Histogram support

[GitBox <gi...@apache.org>]

zentol commented on a change in pull request #14340:
URL: https://github.com/apache/flink/pull/14340#discussion_r540933465



##########
File path: flink-metrics/flink-metrics-datadog/src/main/java/org/apache/flink/metrics/datadog/DHistogram.java
##########
@@ -0,0 +1,61 @@
+/*
+ * 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.flink.metrics.datadog;
+
+import org.apache.flink.metrics.Histogram;
+import org.apache.flink.metrics.HistogramStatistics;
+
+import java.util.List;
+
+/**
+ * Maps histograms to datadog gauges.
+ *
+ * <p>Note: We cannot map them to datadog histograms because the HTTP API does not support them.
+ */
+public class DHistogram {
+	private final Histogram histogram;
+	private final MetricMetaData metaData;
+
+	public DHistogram(Histogram histogram, String metricName, String host, List<String> tags, Clock clock) {
+		this.histogram = histogram;
+		this.metaData = new MetricMetaData(MetricType.gauge, metricName, host, tags, clock);
+	}
+
+	public void addTo(DSeries series) {
+		final HistogramStatistics statistics = histogram.getStatistics();
+
+		// this selection is based on https://docs.datadoghq.com/developers/metrics/types/?tab=histogram
+		// we only exclude 'sum' (which is optional), because we cannot compute it
+		// the semantics for count are also slightly different, because we don't reset it after a report
+		series.add(new StaticDMetric(statistics.getMean(), withMetricNameSuffix(metaData, "avg")));
+		series.add(new StaticDMetric(histogram.getCount(), withMetricNameSuffix(metaData, "count")));
+		series.add(new StaticDMetric(statistics.getQuantile(.5), withMetricNameSuffix(metaData, "median")));
+		series.add(new StaticDMetric(statistics.getQuantile(.95), withMetricNameSuffix(metaData, "95percentile")));
+		series.add(new StaticDMetric(statistics.getMin(), withMetricNameSuffix(metaData, "min")));
+		series.add(new StaticDMetric(statistics.getMax(), withMetricNameSuffix(metaData, "max")));

Review comment:
       Yes, we should do this only once in the constructor; it's a waste of resources to do this every time.




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