Allow Prometheus exporter to add resource attributes to metric attrib…

…utes (#6179)

exporters/prometheus/src/main/java/io/opentelemetry/exporter/prometheus/PrometheusHttpServer.java

@@ -23,6 +23,7 @@
 import java.net.InetSocketAddress;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.TimeUnit;
+import java.util.function.Predicate;
 import javax.annotation.Nullable;
 
 /**
@@ -55,8 +56,10 @@ public static PrometheusHttpServerBuilder builder() {
       int port,
       @Nullable ExecutorService executor,
       PrometheusRegistry prometheusRegistry,
-      boolean otelScopeEnabled) {
-    this.prometheusMetricReader = new PrometheusMetricReader(otelScopeEnabled);
+      boolean otelScopeEnabled,
+      @Nullable Predicate<String> allowedResourceAttributesFilter) {
+    this.prometheusMetricReader =
+        new PrometheusMetricReader(otelScopeEnabled, allowedResourceAttributesFilter);
     this.host = host;
     this.prometheusRegistry = prometheusRegistry;
     prometheusRegistry.register(prometheusMetricReader);

exporters/prometheus/src/main/java/io/opentelemetry/exporter/prometheus/PrometheusHttpServerBuilder.java

@@ -10,6 +10,7 @@
 
 import io.prometheus.metrics.model.registry.PrometheusRegistry;
 import java.util.concurrent.ExecutorService;
+import java.util.function.Predicate;
 import javax.annotation.Nullable;
 
 /** A builder for {@link PrometheusHttpServer}. */
@@ -22,7 +23,7 @@ public final class PrometheusHttpServerBuilder {
   private int port = DEFAULT_PORT;
   private PrometheusRegistry prometheusRegistry = new PrometheusRegistry();
   private boolean otelScopeEnabled = true;
-
+  @Nullable private Predicate<String> allowedResourceAttributesFilter;
   @Nullable private ExecutorService executor;
 
   /** Sets the host to bind to. If unset, defaults to {@value #DEFAULT_HOST}. */
@@ -60,12 +61,34 @@ public PrometheusHttpServerBuilder setOtelScopeEnabled(boolean otelScopeEnabled)
     return this;
   }
 
+  /**
+   * Set if the resource attributes should be added as labels on each exported metric.
+   *
+   * <p>If set, resource attributes will be added as labels on each exported metric if their key
+   * tests positive (true) when passed through {@code resourceAttributesFilter}.
+   *
+   * @param resourceAttributesFilter a predicate that returns true if the resource attribute should
+   *     be added as a label on each exported metric. The predicates input is the resource attribute
+   *     key.
+   */
+  public PrometheusHttpServerBuilder setAllowedResourceAttributesFilter(
+      Predicate<String> resourceAttributesFilter) {
+    this.allowedResourceAttributesFilter = requireNonNull(resourceAttributesFilter);
+    return this;
+  }
+
   /**
    * Returns a new {@link PrometheusHttpServer} with the configuration of this builder which can be
    * registered with a {@link io.opentelemetry.sdk.metrics.SdkMeterProvider}.
    */
   public PrometheusHttpServer build() {
-    return new PrometheusHttpServer(host, port, executor, prometheusRegistry, otelScopeEnabled);
+    return new PrometheusHttpServer(
+        host,
+        port,
+        executor,
+        prometheusRegistry,
+        otelScopeEnabled,
+        allowedResourceAttributesFilter);
   }
 
   PrometheusHttpServerBuilder() {}

exporters/prometheus/src/main/java/io/opentelemetry/exporter/prometheus/PrometheusMetricReader.java

@@ -12,6 +12,8 @@
 import io.opentelemetry.sdk.metrics.export.MetricReader;
 import io.prometheus.metrics.model.registry.MultiCollector;
 import io.prometheus.metrics.model.snapshots.MetricSnapshots;
+import java.util.function.Predicate;
+import javax.annotation.Nullable;
 
 /**
  * This is the bridge between Prometheus and OpenTelemetry.
@@ -26,9 +28,12 @@ public class PrometheusMetricReader implements MetricReader, MultiCollector {
   private volatile CollectionRegistration collectionRegistration = CollectionRegistration.noop();
   private final Otel2PrometheusConverter converter;
 
-  /** See {@link Otel2PrometheusConverter#Otel2PrometheusConverter(boolean)}. */
-  public PrometheusMetricReader(boolean otelScopeEnabled) {
-    this.converter = new Otel2PrometheusConverter(otelScopeEnabled);
+  // TODO: refactor to public static create or builder pattern to align with project style
+  /** See {@link Otel2PrometheusConverter#Otel2PrometheusConverter(boolean, Predicate)}. */
+  public PrometheusMetricReader(
+      boolean otelScopeEnabled, @Nullable Predicate<String> allowedResourceAttributesFilter) {
+    this.converter =
+        new Otel2PrometheusConverter(otelScopeEnabled, allowedResourceAttributesFilter);
   }
 
   @Override

exporters/prometheus/src/main/java/io/opentelemetry/exporter/prometheus/internal/PrometheusMetricReaderProvider.java

@@ -31,6 +31,7 @@ public MetricReader createMetricReader(ConfigProperties config) {
     if (host != null) {
       prometheusBuilder.setHost(host);
     }
+
     return prometheusBuilder.build();
   }