Address review comments

Author: steverao

docs/apidiffs/current_vs_latest/opentelemetry-instrumentation-api.txt

@@ -1,18 +1,10 @@
 Comparing source compatibility of opentelemetry-instrumentation-api-2.17.0-SNAPSHOT.jar against opentelemetry-instrumentation-api-2.16.0.jar
-+++  NEW INTERFACE: PUBLIC(+) ABSTRACT(+) io.opentelemetry.instrumentation.api.instrumenter.AttributesExtractorCustomizer  (not serializable)
++++  NEW INTERFACE: PUBLIC(+) ABSTRACT(+) io.opentelemetry.instrumentation.api.instrumenter.InstrumentationCustomizer  (not serializable)
 	+++  CLASS FILE FORMAT VERSION: 52.0 <- n.a.
 	+++  NEW SUPERCLASS: java.lang.Object
-	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) io.opentelemetry.instrumentation.api.instrumenter.AttributesExtractor<REQUEST,RESPONSE> get()
+	+++  NEW METHOD: PUBLIC(+) io.opentelemetry.instrumentation.api.instrumenter.AttributesExtractor<REQUEST,RESPONSE> getAttributesExtractor()
 		GENERIC TEMPLATES: +++ REQUEST:java.lang.Object, +++ RESPONSE:java.lang.Object
-	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) java.util.List<java.lang.String> instrumentationNames()
-+++  NEW INTERFACE: PUBLIC(+) ABSTRACT(+) io.opentelemetry.instrumentation.api.instrumenter.ContextCustomizerCustomizer  (not serializable)
-	+++  CLASS FILE FORMAT VERSION: 52.0 <- n.a.
-	+++  NEW SUPERCLASS: java.lang.Object
-	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) io.opentelemetry.instrumentation.api.instrumenter.ContextCustomizer<REQUEST> get()
+	+++  NEW METHOD: PUBLIC(+) io.opentelemetry.instrumentation.api.instrumenter.ContextCustomizer<REQUEST> getContextCustomizer()
 		GENERIC TEMPLATES: +++ REQUEST:java.lang.Object
-	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) java.util.List<java.lang.String> instrumentationNames()
-+++  NEW INTERFACE: PUBLIC(+) ABSTRACT(+) io.opentelemetry.instrumentation.api.instrumenter.OperationMetricsCustomizer  (not serializable)
-	+++  CLASS FILE FORMAT VERSION: 52.0 <- n.a.
-	+++  NEW SUPERCLASS: java.lang.Object
-	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) io.opentelemetry.instrumentation.api.instrumenter.OperationMetrics get()
-	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) java.util.List<java.lang.String> instrumentationNames()
+	+++  NEW METHOD: PUBLIC(+) io.opentelemetry.instrumentation.api.instrumenter.OperationMetrics getOperationMetrics()
+	+++  NEW METHOD: PUBLIC(+) ABSTRACT(+) java.util.function.Predicate<java.lang.String> instrumentationNamePredicate()

instrumentation-api/src/main/java/io/opentelemetry/instrumentation/api/instrumenter/AttributesExtractorCustomizer.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.instrumentation.api.instrumenter;
+
+import java.util.function.Predicate;
+
+/**
+ * A service provider interface (SPI) for providing customizations for instrumentation, including
+ * operation metrics, attributes extraction, and context customization.
+ *
+ * <p>This allows external modules or plugins to contribute custom logic for specific instrumented
+ * libraries, without modifying core instrumentation code.
+ */
+public interface InstrumentationCustomizer {
+
+  /**
+   * Returns a predicate that determines whether this customizer supports a given instrumentation
+   * name.
+   *
+   * <p>The customizer will only be applied if the current instrumentation name matches the
+   * predicate. For example, the predicate might match names like "io.opentelemetry.netty-3.8" or
+   * "io.opentelemetry.apache-httpclient-4.3".
+   *
+   * @return a predicate for supported instrumentation names
+   */
+  Predicate<String> instrumentationNamePredicate();
+
+  /**
+   * Returns a new instance of an {@link OperationMetrics} that will record metrics for the
+   * instrumented operation.
+   *
+   * @return an operation metrics instance, or null if not applicable
+   */
+  default OperationMetrics getOperationMetrics() {
+    return null;
+  }
+
+  /**
+   * Returns a new instance of an {@link AttributesExtractor} that will extract attributes from
+   * requests and responses during the instrumentation process.
+   *
+   * @param <REQUEST> the type of request object used by the instrumented library
+   * @param <RESPONSE> the type of response object used by the instrumented library
+   * @return an attributes extractor instance, or null if not applicable
+   */
+  default <REQUEST, RESPONSE> AttributesExtractor<REQUEST, RESPONSE> getAttributesExtractor() {
+    return null;
+  }
+
+  /**
+   * Returns a new instance of a {@link ContextCustomizer} that will customize the tracing context
+   * during request processing.
+   *
+   * @param <REQUEST> the type of request object used by the instrumented library
+   * @return a context customizer instance, or null if not applicable
+   */
+  default <REQUEST> ContextCustomizer<REQUEST> getContextCustomizer() {
+    return null;
+  }
+}

instrumentation-api/src/main/java/io/opentelemetry/instrumentation/api/instrumenter/ContextCustomizerCustomizer.java

@@ -32,6 +32,7 @@
 import java.util.Map;
 import java.util.ServiceLoader;
 import java.util.Set;
+import java.util.function.Predicate;
 import java.util.logging.Logger;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
@@ -72,43 +73,18 @@ public final class InstrumenterBuilder<REQUEST, RESPONSE> {
   boolean propagateOperationListenersToOnEnd = false;
   boolean enabled = true;
 
-  private static final Map<String, List<ContextCustomizerCustomizer>> CONTEXT_CUSTOMIZER_MAP =
-      new HashMap<>();
-  private static final Map<String, List<AttributesExtractorCustomizer>> ATTRIBUTES_EXTRACTOR_MAP =
-      new HashMap<>();
-  private static final Map<String, List<OperationMetricsCustomizer>> OPERATION_METRICS_MAP =
-      new HashMap<>();
+  private static final Map<Predicate<String>, List<InstrumentationCustomizer>>
+      INSTRUMENTATION_CUSTOMIZER_MAP = new HashMap<>();
 
   static {
-    ServiceLoader.load(ContextCustomizerCustomizer.class)
-        .forEach(
-            customizers -> {
-              for (String name : customizers.instrumentationNames()) {
-                CONTEXT_CUSTOMIZER_MAP
-                    .computeIfAbsent(name, k -> new ArrayList<>())
-                    .add(customizers);
-              }
-            });
-
-    ServiceLoader.load(AttributesExtractorCustomizer.class)
-        .forEach(
-            customizers -> {
-              for (String name : customizers.instrumentationNames()) {
-                ATTRIBUTES_EXTRACTOR_MAP
-                    .computeIfAbsent(name, k -> new ArrayList<>())
-                    .add(customizers);
-              }
-            });
-
-    ServiceLoader.load(OperationMetricsCustomizer.class)
-        .forEach(
-            customizers -> {
-              for (String name : customizers.instrumentationNames()) {
-                OPERATION_METRICS_MAP
-                    .computeIfAbsent(name, k -> new ArrayList<>())
-                    .add(customizers);
-              }
-            });
+    ServiceLoader<InstrumentationCustomizer> serviceLoader =
+        ServiceLoader.load(InstrumentationCustomizer.class);
+
+    for (InstrumentationCustomizer customizer : serviceLoader) {
+      INSTRUMENTATION_CUSTOMIZER_MAP
+          .computeIfAbsent(customizer.instrumentationNamePredicate(), k -> new ArrayList<>())
+          .add(customizer);
+    }
   }
 
   InstrumenterBuilder(
@@ -120,30 +96,6 @@ public final class InstrumenterBuilder<REQUEST, RESPONSE> {
     this.spanNameExtractor = spanNameExtractor;
     this.instrumentationVersion =
         EmbeddedInstrumentationProperties.findVersion(instrumentationName);
-
-    List<ContextCustomizerCustomizer> contextProviders =
-        CONTEXT_CUSTOMIZER_MAP.get(instrumentationName);
-    if (contextProviders != null) {
-      for (ContextCustomizerCustomizer provider : contextProviders) {
-        addContextCustomizer(provider.get());
-      }
-    }
-
-    List<AttributesExtractorCustomizer> attributeProviders =
-        ATTRIBUTES_EXTRACTOR_MAP.get(instrumentationName);
-    if (attributeProviders != null) {
-      for (AttributesExtractorCustomizer provider : attributeProviders) {
-        addAttributesExtractor(provider.get());
-      }
-    }
-
-    List<OperationMetricsCustomizer> metricsProviders =
-        OPERATION_METRICS_MAP.get(instrumentationName);
-    if (metricsProviders != null) {
-      for (OperationMetricsCustomizer provider : metricsProviders) {
-        addOperationMetrics(provider.get());
-      }
-    }
   }
 
   /**
@@ -347,6 +299,25 @@ public Instrumenter<REQUEST, RESPONSE> buildInstrumenter(
   private Instrumenter<REQUEST, RESPONSE> buildInstrumenter(
       InstrumenterConstructor<REQUEST, RESPONSE> constructor,
       SpanKindExtractor<? super REQUEST> spanKindExtractor) {
+    List<InstrumentationCustomizer> customizers =
+        INSTRUMENTATION_CUSTOMIZER_MAP.entrySet().stream()
+            .filter(entry -> entry.getKey().test(instrumentationName))
+            .map(Map.Entry::getValue)
+            .findFirst()
+            .orElse(null);
+    if (customizers != null) {
+      for (InstrumentationCustomizer customizer : customizers) {
+        if (customizer.getContextCustomizer() != null) {
+          addContextCustomizer(customizer.getContextCustomizer());
+        }
+        if (customizer.getAttributesExtractor() != null) {
+          addAttributesExtractor(customizer.getAttributesExtractor());
+        }
+        if (customizer.getOperationMetrics() != null) {
+          addOperationMetrics(customizer.getOperationMetrics());
+        }
+      }
+    }
     this.spanKindExtractor = spanKindExtractor;
     return constructor.create(this);
   }