feat: support metric name filtering in OpenTelemetry exporter

docs/content/otel/otlp.md

@@ -44,6 +44,9 @@ By default, the `OpenTelemetryExporter` will push metrics every 60 seconds to
 the [OpenTelemetryExporter.Builder][builder-javadoc], or at runtime via
 [`io.prometheus.exporter.opentelemetry.*`][otel-properties] properties.
 
+The OpenTelemetry exporter also honors the shared [`io.prometheus.exporter.filter.*`][exporter-filter-properties] metric-name
+filter properties.
+
 In addition to the Prometheus Java client configuration, the exporter also recognizes standard
 OpenTelemetry configuration. For example, you can set
 the [OTEL_EXPORTER_OTLP_METRICS_ENDPOINT](https://opentelemetry.io/docs/concepts/sdk-configuration/otlp-exporter-configuration/#otel_exporter_otlp_metrics_endpoint)
@@ -62,4 +65,5 @@ OTel collector, and a Prometheus server.
 [builder-javadoc]: /client_java/api/io/prometheus/metrics/exporter/opentelemetry/OpenTelemetryExporter.Builder.html
 [opentelemetry-example]: https://github.com/prometheus/client_java/tree/main/examples/example-exporter-opentelemetry
 [otel-pipeline]: /client_java/images/otel-pipeline.png
+[exporter-filter-properties]: {{< relref "../config/config.md#exporter-filter-properties" >}}
 [otel-properties]: {{< relref "../config/config.md#exporter-opentelemetry-properties" >}}

prometheus-metrics-exporter-opentelemetry/src/main/java/io/prometheus/metrics/exporter/opentelemetry/OtelAutoConfig.java

@@ -40,8 +40,10 @@ static MetricReader createReader(
     MetricReader reader = requireNonNull(readerRef.get());
     boolean preserveNames = resolvePreserveNames(builder, config);
     reader.register(
-        new PrometheusMetricProducer(
-            registry, instrumentationScopeInfo, getResourceField(sdk), preserveNames));
+        PrometheusMetricProducer.builder(
+                registry, instrumentationScopeInfo, getResourceField(sdk), preserveNames)
+            .exporterFilterProperties(config.getExporterFilterProperties())
+            .build());
     return reader;
   }
 

prometheus-metrics-exporter-opentelemetry/src/main/java/io/prometheus/metrics/exporter/opentelemetry/PrometheusMetricProducer.java

@@ -7,7 +7,9 @@
 import io.opentelemetry.sdk.metrics.export.CollectionRegistration;
 import io.opentelemetry.sdk.resources.Resource;
 import io.opentelemetry.sdk.resources.ResourceBuilder;
+import io.prometheus.metrics.config.ExporterFilterProperties;
 import io.prometheus.metrics.exporter.opentelemetry.otelmodel.MetricDataFactory;
+import io.prometheus.metrics.model.registry.MetricNameFilter;
 import io.prometheus.metrics.model.registry.PrometheusRegistry;
 import io.prometheus.metrics.model.snapshots.CounterSnapshot;
 import io.prometheus.metrics.model.snapshots.GaugeSnapshot;
@@ -22,6 +24,7 @@
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
+import java.util.function.Predicate;
 import javax.annotation.Nullable;
 
 class PrometheusMetricProducer implements CollectionRegistration {
@@ -30,29 +33,65 @@ class PrometheusMetricProducer implements CollectionRegistration {
   private final Resource resource;
   private final InstrumentationScopeInfo instrumentationScopeInfo;
   private final boolean preserveNames;
+  @Nullable private final Predicate<String> nameFilter;
 
-  public PrometheusMetricProducer(
+  private PrometheusMetricProducer(
       PrometheusRegistry registry,
       InstrumentationScopeInfo instrumentationScopeInfo,
       Resource resource,
-      boolean preserveNames) {
+      boolean preserveNames,
+      @Nullable Predicate<String> nameFilter) {
     this.registry = registry;
     this.instrumentationScopeInfo = instrumentationScopeInfo;
     this.resource = resource;
     this.preserveNames = preserveNames;
+    this.nameFilter = nameFilter;
+  }
+
+  /**
+   * Creates a builder for a producer with no metric name filtering by default, i.e. all metrics in
+   * {@code registry} are exported unless filter properties are configured on the builder.
+   */
+  static Builder builder(
+      PrometheusRegistry registry,
+      InstrumentationScopeInfo instrumentationScopeInfo,
+      Resource resource,
+      boolean preserveNames) {
+    return new Builder(registry, instrumentationScopeInfo, resource, preserveNames);
+  }
+
+  /**
+   * Builds a name filter from {@code io.prometheus.exporter.filter.*} properties, mirroring how
+   * {@code PrometheusScrapeHandler} builds its filter for the Servlet/HTTPServer exporters so that
+   * filtering config behaves consistently across exporters.
+   *
+   * <p>OpenTelemetry's own Views API also supports filtering and aggregation, and may be preferable
+   * for OpenTelemetry-specific deployments; this filter is intended for users who want the same
+   * {@code io.prometheus.exporter.filter.*} config to apply regardless of which exporter they use.
+   *
+   * @return {@code null} if no filter properties are set, to avoid the overhead of testing every
+   *     metric name against a filter that matches everything.
+   */
+  @Nullable
+  private static Predicate<String> makeNameFilter(ExporterFilterProperties props) {
+    if (props.getAllowedMetricNames() == null
+        && props.getExcludedMetricNames() == null
+        && props.getAllowedMetricNamePrefixes() == null
+        && props.getExcludedMetricNamePrefixes() == null) {
+      return null;
+    }
+    return MetricNameFilter.builder()
+        .nameMustBeEqualTo(props.getAllowedMetricNames())
+        .nameMustNotBeEqualTo(props.getExcludedMetricNames())
+        .nameMustStartWith(props.getAllowedMetricNamePrefixes())
+        .nameMustNotStartWith(props.getExcludedMetricNamePrefixes())
+        .build();
   }
 
   @Override
   public Collection<MetricData> collectAllMetrics() {
-    // Note: Currently all metrics from the registry are exported. To add metric filtering
-    // similar to the Servlet exporter, one could:
-    // 1. Add filter properties to ExporterOpenTelemetryProperties (allowedNames, excludedNames,
-    // etc.)
-    // 2. Convert these properties to a Predicate<String> using MetricNameFilter.builder()
-    // 3. Call registry.scrape(filter) instead of registry.scrape()
-    // OpenTelemetry also provides its own Views API for filtering and aggregation, which may be
-    // preferred for OpenTelemetry-specific deployments.
-    MetricSnapshots snapshots = registry.scrape();
+    MetricSnapshots snapshots =
+        nameFilter != null ? registry.scrape(nameFilter) : registry.scrape();
     Resource resourceWithTargetInfo = resource.merge(resourceFromTargetInfo(snapshots));
     InstrumentationScopeInfo scopeFromInfo = instrumentationScopeFromOtelScopeInfo(snapshots);
     List<MetricData> result = new ArrayList<>(snapshots.size());
@@ -142,4 +181,37 @@ private void addUnlessNull(List<MetricData> result, @Nullable MetricData data) {
       result.add(data);
     }
   }
+
+  static class Builder {
+    private final PrometheusRegistry registry;
+    private final Resource resource;
+    private final InstrumentationScopeInfo instrumentationScopeInfo;
+    private final boolean preserveNames;
+    private ExporterFilterProperties filterProperties = ExporterFilterProperties.builder().build();
+
+    private Builder(
+        PrometheusRegistry registry,
+        InstrumentationScopeInfo instrumentationScopeInfo,
+        Resource resource,
+        boolean preserveNames) {
+      this.registry = registry;
+      this.instrumentationScopeInfo = instrumentationScopeInfo;
+      this.resource = resource;
+      this.preserveNames = preserveNames;
+    }
+
+    Builder exporterFilterProperties(ExporterFilterProperties filterProperties) {
+      this.filterProperties = filterProperties;
+      return this;
+    }
+
+    PrometheusMetricProducer build() {
+      return new PrometheusMetricProducer(
+          registry,
+          instrumentationScopeInfo,
+          resource,
+          preserveNames,
+          makeNameFilter(filterProperties));
+    }
+  }
 }

prometheus-metrics-exporter-opentelemetry/src/test/java/io/prometheus/metrics/exporter/opentelemetry/ExportTest.java

@@ -12,6 +12,7 @@
 import io.opentelemetry.sdk.testing.assertj.OpenTelemetryAssertions;
 import io.opentelemetry.sdk.testing.exporter.InMemoryMetricReader;
 import io.opentelemetry.sdk.testing.junit5.OpenTelemetryExtension;
+import io.prometheus.metrics.config.ExporterFilterProperties;
 import io.prometheus.metrics.core.metrics.Counter;
 import io.prometheus.metrics.core.metrics.Gauge;
 import io.prometheus.metrics.core.metrics.Histogram;
@@ -46,11 +47,12 @@ void setUp() throws IllegalAccessException, NoSuchFieldException {
     MetricReader reader = (MetricReader) field.get(testing);
 
     PrometheusMetricProducer prometheusMetricProducer =
-        new PrometheusMetricProducer(
-            registry,
-            InstrumentationScopeInfo.create("test"),
-            Resource.create(Attributes.builder().put("staticRes", "value").build()),
-            false);
+        PrometheusMetricProducer.builder(
+                registry,
+                InstrumentationScopeInfo.create("test"),
+                Resource.create(Attributes.builder().put("staticRes", "value").build()),
+                false)
+            .build();
 
     reader.register(prometheusMetricProducer);
   }
@@ -332,11 +334,12 @@ void preserveNamesWithUnit() {
     InMemoryMetricReader reader = InMemoryMetricReader.create();
     PrometheusRegistry preserveRegistry = new PrometheusRegistry();
     reader.register(
-        new PrometheusMetricProducer(
-            preserveRegistry,
-            InstrumentationScopeInfo.create("test"),
-            Resource.create(Attributes.builder().put("staticRes", "value").build()),
-            true));
+        PrometheusMetricProducer.builder(
+                preserveRegistry,
+                InstrumentationScopeInfo.create("test"),
+                Resource.create(Attributes.builder().put("staticRes", "value").build()),
+                true)
+            .build());
 
     Counter.builder().name("req").unit(Unit.BYTES).register(preserveRegistry).inc();
 
@@ -350,11 +353,12 @@ void preserveNamesWithUnitAlreadyInName() {
     InMemoryMetricReader reader = InMemoryMetricReader.create();
     PrometheusRegistry preserveRegistry = new PrometheusRegistry();
     reader.register(
-        new PrometheusMetricProducer(
-            preserveRegistry,
-            InstrumentationScopeInfo.create("test"),
-            Resource.create(Attributes.builder().put("staticRes", "value").build()),
-            true));
+        PrometheusMetricProducer.builder(
+                preserveRegistry,
+                InstrumentationScopeInfo.create("test"),
+                Resource.create(Attributes.builder().put("staticRes", "value").build()),
+                true)
+            .build());
 
     Counter.builder().name("req_bytes").unit(Unit.BYTES).register(preserveRegistry).inc();
 
@@ -368,11 +372,12 @@ void preserveNamesWithoutUnit() {
     InMemoryMetricReader reader = InMemoryMetricReader.create();
     PrometheusRegistry preserveRegistry = new PrometheusRegistry();
     reader.register(
-        new PrometheusMetricProducer(
-            preserveRegistry,
-            InstrumentationScopeInfo.create("test"),
-            Resource.create(Attributes.builder().put("staticRes", "value").build()),
-            true));
+        PrometheusMetricProducer.builder(
+                preserveRegistry,
+                InstrumentationScopeInfo.create("test"),
+                Resource.create(Attributes.builder().put("staticRes", "value").build()),
+                true)
+            .build());
 
     Counter.builder().name("events_total").register(preserveRegistry).inc();
 
@@ -381,6 +386,50 @@ void preserveNamesWithoutUnit() {
     OpenTelemetryAssertions.assertThat(metrics.get(0)).hasName("events_total");
   }
 
+  @Test
+  void metricNameFilterExcludedNames() {
+    InMemoryMetricReader reader = InMemoryMetricReader.create();
+    PrometheusRegistry filteredRegistry = new PrometheusRegistry();
+    reader.register(
+        PrometheusMetricProducer.builder(
+                filteredRegistry,
+                InstrumentationScopeInfo.create("test"),
+                Resource.create(Attributes.builder().put("staticRes", "value").build()),
+                false)
+            .exporterFilterProperties(
+                ExporterFilterProperties.builder().excludedNames("secret_total").build())
+            .build());
+
+    Counter.builder().name("secret").register(filteredRegistry).inc();
+    Counter.builder().name("public").register(filteredRegistry).inc();
+
+    List<MetricData> metrics = new ArrayList<>(reader.collectAllMetrics());
+    assertThat(metrics).hasSize(1);
+    OpenTelemetryAssertions.assertThat(metrics.get(0)).hasName("public");
+  }
+
+  @Test
+  void metricNameFilterAllowedPrefixes() {
+    InMemoryMetricReader reader = InMemoryMetricReader.create();
+    PrometheusRegistry filteredRegistry = new PrometheusRegistry();
+    reader.register(
+        PrometheusMetricProducer.builder(
+                filteredRegistry,
+                InstrumentationScopeInfo.create("test"),
+                Resource.create(Attributes.builder().put("staticRes", "value").build()),
+                false)
+            .exporterFilterProperties(
+                ExporterFilterProperties.builder().allowedPrefixes("http_").build())
+            .build());
+
+    Counter.builder().name("http_requests").register(filteredRegistry).inc();
+    Counter.builder().name("jvm_threads").register(filteredRegistry).inc();
+
+    List<MetricData> metrics = new ArrayList<>(reader.collectAllMetrics());
+    assertThat(metrics).hasSize(1);
+    OpenTelemetryAssertions.assertThat(metrics.get(0)).hasName("http_requests");
+  }
+
   private MetricAssert metricAssert() {
     List<MetricData> metrics = testing.getMetrics();
     assertThat(metrics).hasSize(1);