Make per-meter OTLP configuration more flexible (#6102)

The previous logic for matching required the exact meter name, which was straightforward but cumbersome for configuring groups of meters. This changes the default matching for the per-meter config to use the longest dot-separated segments match. See the updated JavaDocs on the OtlpConfig methods.

Co-authored-by: Jonatan Ivanov <[email protected]>

Author: shakuzen

Diff for: implementations/micrometer-registry-otlp/src/main/java/io/micrometer/registry/otlp/OtlpConfig.java

@@ -15,12 +15,13 @@
  */
 package io.micrometer.registry.otlp;
 
+import io.micrometer.core.instrument.Meter;
 import io.micrometer.core.instrument.config.InvalidConfigurationException;
 import io.micrometer.core.instrument.config.validate.Validated;
 import io.micrometer.core.instrument.push.PushRegistryConfig;
 
-import java.time.Duration;
 import java.net.URLDecoder;
+import java.time.Duration;
 import java.util.*;
 import java.util.concurrent.TimeUnit;
 import java.util.stream.Collectors;
@@ -228,10 +229,16 @@ default HistogramFlavor histogramFlavor() {
     }
 
     /**
-     * Configures the histogram flavor to use on a per-meter level. This will override the
-     * {@link #histogramFlavor()} configuration for matching Meters. The key is used to do
-     * an exact match on the Meter's name.
-     * @return mapping of meter name to histogram flavor
+     * Configures the histogram flavor mapping to use on a per-meter level. This can
+     * override the {@link #histogramFlavor()} configuration for matching Meters.
+     * {@link OtlpMeterRegistry} uses the result of this method to look up the
+     * {@link HistogramFlavor} by {@link Meter.Id}. The longest dot-separated match wins.
+     * For example, if the returned Map has keys {@literal http} and
+     * {@literal http.server}, an ID with a name {@literal http.server.requests} would
+     * match with the entry having key {@literal http.server}, whereas an ID with name
+     * {@literal http.client.requests} would match with the entry having the key
+     * {@literal http}.
+     * @return mapping of meter name (or prefix) to histogram flavor
      * @since 1.15.0
      * @see #histogramFlavor()
      */
@@ -266,10 +273,15 @@ default int maxBucketCount() {
     }
 
     /**
-     * Configures the max bucket count to use on a per-meter level. This will override the
-     * {@link #maxBucketCount()} configuration for matching Meters. The key is used to do
-     * an exact match on the Meter's name. This has no effect on a meter if it does not
-     * have an exponential bucket histogram configured.
+     * Configures the max bucket count mapping to use on a per-meter level. This can
+     * override the {@link #maxBucketCount()} configuration for matching Meters.
+     * {@link OtlpMeterRegistry} uses the result of this method to look up the max bucket
+     * count by {@link Meter.Id}. The longest dot-separated match wins. For example, if
+     * the returned Map has keys {@literal http} and {@literal http.server}, an ID with a
+     * name {@literal http.server.requests} would match with the entry having key
+     * {@literal http.server}, whereas an ID with name {@literal http.client.requests}
+     * would match with the entry having the key {@literal http}. 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 #maxBucketCount()

Diff for: implementations/micrometer-registry-otlp/src/main/java/io/micrometer/registry/otlp/OtlpMeterRegistry.java

@@ -16,10 +16,11 @@
 package io.micrometer.registry.otlp;
 
 import io.micrometer.common.lang.Nullable;
+import io.micrometer.common.util.StringUtils;
 import io.micrometer.common.util.internal.logging.InternalLogger;
 import io.micrometer.common.util.internal.logging.InternalLoggerFactory;
-import io.micrometer.core.instrument.Timer;
 import io.micrometer.core.instrument.*;
+import io.micrometer.core.instrument.Timer;
 import io.micrometer.core.instrument.config.NamingConvention;
 import io.micrometer.core.instrument.distribution.*;
 import io.micrometer.core.instrument.distribution.pause.PauseDetector;
@@ -82,6 +83,10 @@ 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;
@@ -120,6 +125,8 @@ private OtlpMeterRegistry(OtlpConfig config, Clock clock, ThreadFactory threadFa
         this.config = config;
         this.baseTimeUnit = config.baseTimeUnit();
         this.metricsSender = metricsSender;
+        this.histogramFlavorPerMeterLookup = HistogramFlavorPerMeterLookup.DEFAULT;
+        this.maxBucketsPerMeterLookup = MaxBucketsPerMeterLookup.DEFAULT;
         this.resource = Resource.newBuilder().addAllAttributes(getResourceAttributes()).build();
         this.aggregationTemporality = config.aggregationTemporality();
         config().namingConvention(NamingConvention.dot);
@@ -430,14 +437,16 @@ private Histogram getHistogram(Meter.Id id, DistributionStatisticConfig distribu
     }
 
     private int getMaxBuckets(Meter.Id id) {
-        return config.maxBucketsPerMeter().getOrDefault(id.getName(), config.maxBucketCount());
+        Integer maxBuckets = maxBucketsPerMeterLookup.getMaxBuckets(config.maxBucketsPerMeter(), id);
+        return (maxBuckets == null) ? config.maxBucketCount() : maxBuckets;
     }
 
     private HistogramFlavor histogramFlavor(Meter.Id id, OtlpConfig otlpConfig,
             DistributionStatisticConfig distributionStatisticConfig) {
-        HistogramFlavor preferredHistogramFlavor = otlpConfig.histogramFlavorPerMeter()
-            .getOrDefault(id.getName(), otlpConfig.histogramFlavor());
-
+        HistogramFlavor preferredHistogramFlavor = histogramFlavorPerMeterLookup
+            .getHistogramFlavor(otlpConfig.histogramFlavorPerMeter(), id);
+        preferredHistogramFlavor = preferredHistogramFlavor == null ? otlpConfig.histogramFlavor()
+                : preferredHistogramFlavor;
         final double[] serviceLevelObjectiveBoundaries = distributionStatisticConfig
             .getServiceLevelObjectiveBoundaries();
         if (distributionStatisticConfig.isPublishingHistogram()
@@ -497,6 +506,91 @@ static double[] getSloWithPositiveInf(DistributionStatisticConfig distributionSt
         return sloWithPositiveInf;
     }
 
+    /**
+     * Overridable lookup mechanism for {@link HistogramFlavor}.
+     */
+    // VisibleForTesting
+    @FunctionalInterface
+    interface HistogramFlavorPerMeterLookup {
+
+        /**
+         * Default implementation.
+         */
+        HistogramFlavorPerMeterLookup DEFAULT = OtlpMeterRegistry::lookup;
+
+        /**
+         * Looks up the histogram flavor to use on a per-meter level. This will override
+         * the default {@link OtlpConfig#histogramFlavor()} for matching Meters.
+         * {@link OtlpConfig#histogramFlavorPerMeter()} provides the data while this
+         * method provides the logic for the lookup, and you can override them
+         * independently.
+         * @param perMeterMapping configured mapping data
+         * @param id the {@link Meter.Id} the {@link HistogramFlavor} is configured for
+         * @return the histogram flavor mapped to the {@link Meter.Id} or {@code null} if
+         * mapping is undefined
+         * @see OtlpConfig#histogramFlavorPerMeter()
+         * @see OtlpConfig#histogramFlavor()
+         */
+        @Nullable
+        HistogramFlavor getHistogramFlavor(Map<String, HistogramFlavor> perMeterMapping, 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.
+     */
+    // VisibleForTesting
+    @FunctionalInterface
+    interface MaxBucketsPerMeterLookup {
+
+        /**
+         * Default implementation.
+         */
+        MaxBucketsPerMeterLookup DEFAULT = OtlpMeterRegistry::lookup;
+
+        /**
+         * Looks up the max bucket count to use on a per-meter level. This will override
+         * the default {@link OtlpConfig#maxBucketCount()} for matching Meters.
+         * {@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 perMeterMapping configured mapping data
+         * @param id the {@link Meter.Id} the max bucket count is configured for
+         * @return the max bucket count mapped to the {@link Meter.Id} or {@code null} if
+         * the mapping is undefined
+         * @see OtlpConfig#maxBucketsPerMeter()
+         * @see OtlpConfig#maxBucketCount()
+         */
+        @Nullable
+        Integer getMaxBuckets(Map<String, Integer> perMeterMapping, Meter.Id id);
+
+    }
+
+    @Nullable
+    private static <T> T lookup(Map<String, T> values, Meter.Id id) {
+        if (values.isEmpty()) {
+            return null;
+        }
+        return doLookup(values, id);
+    }
+
+    @Nullable
+    private static <T> T doLookup(Map<String, T> values, Meter.Id id) {
+        String name = id.getName();
+        while (StringUtils.isNotEmpty(name)) {
+            T result = values.get(name);
+            if (result != null) {
+                return result;
+            }
+            int lastDot = name.lastIndexOf('.');
+            name = (lastDot != -1) ? name.substring(0, lastDot) : "";
+        }
+
+        return null;
+    }
+
     /**
      * Builder for {@link OtlpMeterRegistry}.
      *

Diff for: implementations/micrometer-registry-otlp/src/test/java/io/micrometer/registry/otlp/OtlpConfigTest.java

@@ -25,9 +25,9 @@
 import java.util.concurrent.TimeUnit;
 import java.util.stream.Stream;
 
-import static java.util.Map.entry;
-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;
 
@@ -257,24 +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
@@ -284,9 +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()).containsExactly(
-                entry("a.b.c", HistogramFlavor.EXPLICIT_BUCKET_HISTOGRAM),
-                entry("expo", HistogramFlavor.BASE2_EXPONENTIAL_BUCKET_HISTOGRAM));
+        assertThat(otlpConfig.histogramFlavorPerMeter()).containsExactly(entry("a.b.c", EXPLICIT_BUCKET_HISTOGRAM),
+                entry("expo", BASE2_EXPONENTIAL_BUCKET_HISTOGRAM));
     }
 
     @Test