Add HistogramFlavorPerMeterLookup and MaxBucketsPerMeterLookup

jonatan-ivanov · jonatan-ivanov · commit 9807805c8989 · 2025-04-11T17:56:47.000-07:00
diff --git a/implementations/micrometer-registry-otlp/src/main/java/io/micrometer/registry/otlp/OtlpConfig.java b/implementations/micrometer-registry-otlp/src/main/java/io/micrometer/registry/otlp/OtlpConfig.java
@@ -231,38 +231,23 @@ default HistogramFlavor histogramFlavor() {
     /**
      * Configures the histogram flavor mapping to use on a per-meter level. This can
      * override the {@link #histogramFlavor()} configuration for matching Meters. By
-     * default, {@link #histogramFlavorPerMeter(Meter.Id)} uses the result of this method
-     * to look up the {@link HistogramFlavor} by {@link Meter.Id} (exact match on the
-     * Meter's name by default). This means that this method provides the data while
-     * {@link #histogramFlavorPerMeter(Meter.Id)} provides the logic for the lookup, and
-     * you can override them independently.
+     * default, {@link OtlpMeterRegistry} (through
+     * {@link io.micrometer.registry.otlp.OtlpMeterRegistry.HistogramFlavorPerMeterLookup})
+     * uses the result of this method to look up the {@link HistogramFlavor} by
+     * {@link Meter.Id} (prefix match on the Meter's name by default). This means that
+     * this method provides the data while
+     * {@link io.micrometer.registry.otlp.OtlpMeterRegistry.HistogramFlavorPerMeterLookup}
+     * provides the logic for the lookup, and you can override them independently.
      * @return mapping of meter name to histogram flavor
      * @since 1.15.0
-     * @see #histogramFlavorPerMeter(Meter.Id)
+     * @see io.micrometer.registry.otlp.OtlpMeterRegistry.HistogramFlavorPerMeterLookup
      * @see #histogramFlavor()
      */
     default Map<String, HistogramFlavor> histogramFlavorPerMeter() {
         return getStringMap(this, "histogramFlavorPerMeter", HistogramFlavor::fromString)
             .orElse(Collections.emptyMap());
     }
 
-    /**
-     * Looks up the histogram flavor to use on a per-meter level. This will override the
-     * {@link #histogramFlavor()} lookup behavior for matching Meters. By default, the key
-     * is used to do an exact match on the Meter's name in the map that
-     * {@link #histogramFlavorPerMeter()} returns. This means that
-     * {@link #histogramFlavorPerMeter()} provides the data while this method provides the
-     * logic for the lookup, and you can override them independently.
-     * @param id the {@link Meter.Id} the {@link HistogramFlavor} is configured for
-     * @return the histogram flavor mapped to the {@link Meter.Id}
-     * @since 1.15.0
-     * @see #histogramFlavorPerMeter()
-     * @see #histogramFlavor()
-     */
-    default HistogramFlavor histogramFlavorPerMeter(Meter.Id id) {
-        return histogramFlavorPerMeter().getOrDefault(id.getName(), histogramFlavor());
-    }
-
     /**
      * Max scale to use for exponential histograms, if configured.
      * @return maxScale
@@ -291,39 +276,24 @@ default int maxBucketCount() {
     /**
      * Configures the max bucket count mapping to use on a per-meter level. This can
      * override the {@link #maxBucketCount()} configuration for matching Meters. By
-     * default {@link #maxBucketsPerMeter(Meter.Id)} uses the result of this method to
-     * look up the max bucket count by {@link Meter.Id} (exact match on the Meter's name
-     * by default). This means that this method provides the data while
-     * {@link #maxBucketsPerMeter(Meter.Id)} provides the logic for the lookup, and you
-     * can override them independently. This has no effect on a meter if it does not have
-     * an exponential bucket histogram configured.
+     * default, {@link OtlpMeterRegistry} (through
+     * {@link io.micrometer.registry.otlp.OtlpMeterRegistry.MaxBucketsPerMeterLookup})
+     * uses the result of this method to look up the max bucket count by {@link Meter.Id}
+     * (prefix match on the Meter's name by default). This means that this method provides
+     * the data while
+     * {@link io.micrometer.registry.otlp.OtlpMeterRegistry.MaxBucketsPerMeterLookup}
+     * provides the logic for the lookup, and you can override them independently. This
+     * has no effect on a meter if it does not have an exponential bucket histogram
+     * configured.
      * @return mapping of meter name to max bucket count
      * @since 1.15.0
-     * @see #maxBucketsPerMeter(Meter.Id)
+     * @see io.micrometer.registry.otlp.OtlpMeterRegistry.MaxBucketsPerMeterLookup
      * @see #maxBucketCount()
      */
     default Map<String, Integer> maxBucketsPerMeter() {
         return getStringMap(this, "maxBucketsPerMeter", Integer::parseInt).orElse(Collections.emptyMap());
     }
 
-    /**
-     * Looks up the max bucket count to use on a per-meter level. This will override the
-     * {@link #maxBucketCount()} lookup behavior for matching Meters. By default, the key
-     * is used to do an exact match on the Meter's name in the map that
-     * {@link #maxBucketsPerMeter()} returns. This means that
-     * {@link #maxBucketsPerMeter()} provides the data while this method provides the
-     * logic for the lookup, and you can override them independently. This has no effect
-     * on a meter if it does not have an exponential bucket histogram configured.
-     * @param id the {@link Meter.Id} the max bucket count is configured for
-     * @return the max bucket count mapped to the {@link Meter.Id}
-     * @since 1.15.0
-     * @see #maxBucketsPerMeter()
-     * @see #maxBucketCount()
-     */
-    default Integer maxBucketsPerMeter(Meter.Id id) {
-        return maxBucketsPerMeter().getOrDefault(id.getName(), maxBucketCount());
-    }
-
     @Override
     default Validated<?> validate() {
         return checkAll(this, c -> PushRegistryConfig.validate(c), checkRequired("url", OtlpConfig::url),
diff --git a/implementations/micrometer-registry-otlp/src/main/java/io/micrometer/registry/otlp/OtlpMeterRegistry.java b/implementations/micrometer-registry-otlp/src/main/java/io/micrometer/registry/otlp/OtlpMeterRegistry.java
@@ -82,6 +82,10 @@ public class OtlpMeterRegistry extends PushMeterRegistry {
 
     private final OtlpMetricsSender metricsSender;
 
+    private final HistogramFlavorPerMeterLookup histogramFlavorPerMeterLookup;
+
+    private final MaxBucketsPerMeterLookup maxBucketsPerMeterLookup;
+
     private final Resource resource;
 
     private final AggregationTemporality aggregationTemporality;
@@ -111,15 +115,19 @@ public OtlpMeterRegistry(OtlpConfig config, Clock clock) {
      * @since 1.14.0
      */
     public OtlpMeterRegistry(OtlpConfig config, Clock clock, ThreadFactory threadFactory) {
-        this(config, clock, threadFactory, new OtlpHttpMetricsSender(new HttpUrlConnectionSender()));
+        this(config, clock, threadFactory, new OtlpHttpMetricsSender(new HttpUrlConnectionSender()),
+                OtlpMeterRegistry::histogramFlavorPerMeter, OtlpMeterRegistry::maxBucketsPerMeter);
     }
 
     private OtlpMeterRegistry(OtlpConfig config, Clock clock, ThreadFactory threadFactory,
-            OtlpMetricsSender metricsSender) {
+            OtlpMetricsSender metricsSender, HistogramFlavorPerMeterLookup histogramFlavorPerMeterLookup,
+            MaxBucketsPerMeterLookup maxBucketsPerMeterLookup) {
         super(config, clock);
         this.config = config;
         this.baseTimeUnit = config.baseTimeUnit();
         this.metricsSender = metricsSender;
+        this.histogramFlavorPerMeterLookup = histogramFlavorPerMeterLookup;
+        this.maxBucketsPerMeterLookup = maxBucketsPerMeterLookup;
         this.resource = Resource.newBuilder().addAllAttributes(getResourceAttributes()).build();
         this.aggregationTemporality = config.aggregationTemporality();
         config().namingConvention(NamingConvention.dot);
@@ -430,16 +438,12 @@ private Histogram getHistogram(Meter.Id id, DistributionStatisticConfig distribu
     }
 
     private int getMaxBuckets(Meter.Id id) {
-        Integer perMeterMaxBuckets = config.maxBucketsPerMeter(id);
-        return perMeterMaxBuckets == null ? config.maxBucketCount() : perMeterMaxBuckets;
+        return maxBucketsPerMeterLookup.getMaxBuckets(config, id);
     }
 
     private HistogramFlavor histogramFlavor(Meter.Id id, OtlpConfig otlpConfig,
             DistributionStatisticConfig distributionStatisticConfig) {
-        HistogramFlavor preferredHistogramFlavor = otlpConfig.histogramFlavorPerMeter(id);
-        preferredHistogramFlavor = preferredHistogramFlavor == null ? otlpConfig.histogramFlavor()
-                : preferredHistogramFlavor;
-
+        HistogramFlavor preferredHistogramFlavor = histogramFlavorPerMeterLookup.getHistogramFlavor(otlpConfig, id);
         final double[] serviceLevelObjectiveBoundaries = distributionStatisticConfig
             .getServiceLevelObjectiveBoundaries();
         if (distributionStatisticConfig.isPublishingHistogram()
@@ -499,6 +503,76 @@ static double[] getSloWithPositiveInf(DistributionStatisticConfig distributionSt
         return sloWithPositiveInf;
     }
 
+    private static HistogramFlavor histogramFlavorPerMeter(OtlpConfig config, Meter.Id id) {
+        for (Map.Entry<String, HistogramFlavor> entry : config.histogramFlavorPerMeter().entrySet()) {
+            if (id.getName().startsWith(entry.getKey())) {
+                return entry.getValue();
+            }
+        }
+        return config.histogramFlavor();
+    }
+
+    private static Integer maxBucketsPerMeter(OtlpConfig config, Meter.Id id) {
+        for (Map.Entry<String, Integer> entry : config.maxBucketsPerMeter().entrySet()) {
+            if (id.getName().startsWith(entry.getKey())) {
+                return entry.getValue();
+            }
+        }
+        return config.maxBucketCount();
+    }
+
+    /**
+     * Overridable lookup mechanism for {@link HistogramFlavor}.
+     *
+     * @since 1.15.0
+     */
+    @FunctionalInterface
+    public interface HistogramFlavorPerMeterLookup {
+
+        /**
+         * Looks up the histogram flavor to use on a per-meter level. This will override
+         * the {@link OtlpConfig#histogramFlavor()} for matching Meters. The default
+         * implementation in {@link OtlpMeterRegistry} does a prefix match on the Meter's
+         * name in the map that {@link OtlpConfig#histogramFlavorPerMeter()} returns. This
+         * means that {@link OtlpConfig#histogramFlavorPerMeter()} provides the data while
+         * this method provides the logic for the lookup, and you can override them
+         * independently.
+         * @param id the {@link Meter.Id} the {@link HistogramFlavor} is configured for
+         * @return the histogram flavor mapped to the {@link Meter.Id}
+         * @see OtlpConfig#histogramFlavorPerMeter()
+         * @see OtlpConfig#histogramFlavor()
+         */
+        HistogramFlavor getHistogramFlavor(OtlpConfig config, Meter.Id id);
+
+    }
+
+    /**
+     * Overridable lookup mechanism for max bucket count. This has no effect on a meter if
+     * it does not have an exponential bucket histogram configured.
+     *
+     * @since 1.15.0
+     */
+    @FunctionalInterface
+    public interface MaxBucketsPerMeterLookup {
+
+        /**
+         * Looks up the max bucket count to use on a per-meter level. This will override
+         * the {@link OtlpConfig#maxBucketCount()} for matching Meters. The default
+         * implementation in {@link OtlpMeterRegistry} does a prefix match on the Meter's
+         * name in the map that {@link OtlpConfig#maxBucketsPerMeter()} returns. This
+         * means that {@link OtlpConfig#maxBucketsPerMeter()} provides the data while this
+         * method provides the logic for the lookup, and you can override them
+         * independently. This has no effect on a meter if it does not have an exponential
+         * bucket histogram configured.
+         * @param id the {@link Meter.Id} the max bucket count is configured for
+         * @return the max bucket count mapped to the {@link Meter.Id}
+         * @see OtlpConfig#maxBucketsPerMeter()
+         * @see OtlpConfig#maxBucketCount()
+         */
+        Integer getMaxBuckets(OtlpConfig config, Meter.Id id);
+
+    }
+
     /**
      * Builder for {@link OtlpMeterRegistry}.
      *
@@ -514,9 +588,15 @@ public static class Builder {
 
         private OtlpMetricsSender metricsSender;
 
+        private HistogramFlavorPerMeterLookup histogramFlavorPerMeterLookup;
+
+        private MaxBucketsPerMeterLookup maxBucketsPerMeterLookup;
+
         private Builder(OtlpConfig otlpConfig) {
             this.otlpConfig = otlpConfig;
             this.metricsSender = new OtlpHttpMetricsSender(new HttpUrlConnectionSender());
+            this.histogramFlavorPerMeterLookup = OtlpMeterRegistry::histogramFlavorPerMeter;
+            this.maxBucketsPerMeterLookup = OtlpMeterRegistry::maxBucketsPerMeter;
         }
 
         /** Override the default clock. */
@@ -542,8 +622,19 @@ public Builder metricsSender(OtlpMetricsSender metricsSender) {
             return this;
         }
 
+        public Builder histogramFlavorPerMeterLookup(HistogramFlavorPerMeterLookup histogramFlavorPerMeterLookup) {
+            this.histogramFlavorPerMeterLookup = histogramFlavorPerMeterLookup;
+            return this;
+        }
+
+        public Builder maxBucketsPerMeterLookup(MaxBucketsPerMeterLookup maxBucketsPerMeterLookup) {
+            this.maxBucketsPerMeterLookup = maxBucketsPerMeterLookup;
+            return this;
+        }
+
         public OtlpMeterRegistry build() {
-            return new OtlpMeterRegistry(otlpConfig, clock, threadFactory, metricsSender);
+            return new OtlpMeterRegistry(otlpConfig, clock, threadFactory, metricsSender, histogramFlavorPerMeterLookup,
+                    maxBucketsPerMeterLookup);
         }
 
     }
diff --git a/implementations/micrometer-registry-otlp/src/test/java/io/micrometer/registry/otlp/OtlpConfigTest.java b/implementations/micrometer-registry-otlp/src/test/java/io/micrometer/registry/otlp/OtlpConfigTest.java
@@ -15,8 +15,6 @@
  */
 package io.micrometer.registry.otlp;
 
-import io.micrometer.core.instrument.Meter;
-import io.micrometer.core.instrument.Tags;
 import io.micrometer.core.instrument.config.InvalidConfigurationException;
 import org.junit.jupiter.api.Test;
 
@@ -27,8 +25,9 @@
 import java.util.concurrent.TimeUnit;
 import java.util.stream.Stream;
 
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static io.micrometer.registry.otlp.HistogramFlavor.BASE2_EXPONENTIAL_BUCKET_HISTOGRAM;
+import static io.micrometer.registry.otlp.HistogramFlavor.EXPLICIT_BUCKET_HISTOGRAM;
+import static org.assertj.core.api.Assertions.*;
 import static uk.org.webcompere.systemstubs.SystemStubs.withEnvironmentVariable;
 import static uk.org.webcompere.systemstubs.SystemStubs.withEnvironmentVariables;
 
@@ -258,24 +257,22 @@ void histogramPreference() {
 
         OtlpConfig otlpConfig = properties::get;
         assertThat(otlpConfig.validate().isValid()).isTrue();
-        assertThat(otlpConfig.histogramFlavor()).isEqualTo(HistogramFlavor.BASE2_EXPONENTIAL_BUCKET_HISTOGRAM);
+        assertThat(otlpConfig.histogramFlavor()).isEqualTo(BASE2_EXPONENTIAL_BUCKET_HISTOGRAM);
     }
 
     @Test
     void histogramPreferenceConfigTakesPrecedenceOverEnvVars() throws Exception {
         OtlpConfig config = k -> "base2_exponential_bucket_histogram";
         withEnvironmentVariable("OTEL_EXPORTER_OTLP_METRICS_DEFAULT_HISTOGRAM_AGGREGATION", "explicit_bucket_histogram")
-            .execute(() -> assertThat(config.histogramFlavor())
-                .isEqualTo(HistogramFlavor.BASE2_EXPONENTIAL_BUCKET_HISTOGRAM));
+            .execute(() -> assertThat(config.histogramFlavor()).isEqualTo(BASE2_EXPONENTIAL_BUCKET_HISTOGRAM));
     }
 
     @Test
     void histogramPreferenceUseEnvVarWhenConfigNotSet() throws Exception {
         OtlpConfig config = k -> null;
         withEnvironmentVariable("OTEL_EXPORTER_OTLP_METRICS_DEFAULT_HISTOGRAM_AGGREGATION",
                 "base2_exponential_bucket_histogram")
-            .execute(() -> assertThat(config.histogramFlavor())
-                .isEqualTo(HistogramFlavor.BASE2_EXPONENTIAL_BUCKET_HISTOGRAM));
+            .execute(() -> assertThat(config.histogramFlavor()).isEqualTo(BASE2_EXPONENTIAL_BUCKET_HISTOGRAM));
     }
 
     @Test
@@ -285,41 +282,8 @@ void histogramFlavorPerMeter() {
                 "a.b.c=explicit_bucket_histogram ,expo =base2_exponential_bucket_histogram");
         OtlpConfig otlpConfig = properties::get;
         assertThat(otlpConfig.validate().isValid()).isTrue();
-        assertThat(otlpConfig.histogramFlavorPerMeter(idWithName("a.b.c")))
-            .isEqualTo(HistogramFlavor.EXPLICIT_BUCKET_HISTOGRAM);
-        assertThat(otlpConfig.histogramFlavorPerMeter(idWithName("expo")))
-            .isEqualTo(HistogramFlavor.BASE2_EXPONENTIAL_BUCKET_HISTOGRAM);
-    }
-
-    @Test
-    void customHistogramFlavorPerMeterFunction() {
-        Map<String, String> properties = new HashMap<>();
-        properties.put("otlp.histogramFlavorPerMeter",
-                "a.b.c=explicit_bucket_histogram,expo=base2_exponential_bucket_histogram");
-        OtlpConfig otlpConfig = new OtlpConfig() {
-            @Override
-            public String get(String key) {
-                return properties.get(key);
-            }
-
-            @Override
-            public HistogramFlavor histogramFlavorPerMeter(Meter.Id id) {
-                for (Map.Entry<String, HistogramFlavor> entry : histogramFlavorPerMeter().entrySet()) {
-                    if (id.getName().startsWith(entry.getKey())) {
-                        return entry.getValue();
-                    }
-                }
-                return histogramFlavor();
-            }
-        };
-        assertThat(otlpConfig.validate().isValid()).isTrue();
-        assertThat(otlpConfig.histogramFlavorPerMeter(idWithName("something"))).isEqualTo(otlpConfig.histogramFlavor());
-        assertThat(otlpConfig.histogramFlavorPerMeter(idWithName("a.b.c")))
-            .isEqualTo(HistogramFlavor.EXPLICIT_BUCKET_HISTOGRAM);
-        assertThat(otlpConfig.histogramFlavorPerMeter(idWithName("expo")))
-            .isEqualTo(HistogramFlavor.BASE2_EXPONENTIAL_BUCKET_HISTOGRAM);
-        assertThat(otlpConfig.histogramFlavorPerMeter(idWithName("expo.other")))
-            .isEqualTo(HistogramFlavor.BASE2_EXPONENTIAL_BUCKET_HISTOGRAM);
+        assertThat(otlpConfig.histogramFlavorPerMeter()).containsExactly(entry("a.b.c", EXPLICIT_BUCKET_HISTOGRAM),
+                entry("expo", BASE2_EXPONENTIAL_BUCKET_HISTOGRAM));
     }
 
     @Test
@@ -328,11 +292,7 @@ void maxBucketsPerMeter() {
         properties.put("otlp.maxBucketsPerMeter", "a.b.c = 10");
         OtlpConfig otlpConfig = properties::get;
         assertThat(otlpConfig.validate().isValid()).isTrue();
-        assertThat(otlpConfig.maxBucketsPerMeter(idWithName("a.b.c"))).isEqualTo(10);
-    }
-
-    Meter.Id idWithName(String name) {
-        return new Meter.Id(name, Tags.empty(), null, null, Meter.Type.OTHER);
+        assertThat(otlpConfig.maxBucketsPerMeter()).containsExactly(entry("a.b.c", 10));
     }
 
 }
diff --git a/implementations/micrometer-registry-otlp/src/test/java/io/micrometer/registry/otlp/OtlpMeterRegistryTest.java b/implementations/micrometer-registry-otlp/src/test/java/io/micrometer/registry/otlp/OtlpMeterRegistryTest.java
