feat(context): prototype context-scoped attributes (#8532)

api/incubator/src/main/java/io/opentelemetry/api/incubator/common/ContextAttributes.java

@@ -0,0 +1,118 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.api.incubator.common;
+
+import io.opentelemetry.api.common.Attributes;
+import io.opentelemetry.common.impl.ApiUsageLogger;
+import io.opentelemetry.context.Context;
+import io.opentelemetry.context.ContextKey;
+import javax.annotation.Nullable;
+
+// TODO (jack-berg): delete after 2027-07-01 if progress hasn't been made on
+// https://github.com/open-telemetry/opentelemetry-specification/pull/4931
+/**
+ * Utility for associating {@link Attributes} with a {@link Context} for automatic propagation to
+ * telemetry signals produced within that context.
+ *
+ * <p>SDKs can be configured to stamp context-scoped attributes across telemetry signals, with the
+ * ability to filter based on signal, instrumentation scope, and attribute key.
+ *
+ * <h2>Cardinality Considerations</h2>
+ *
+ * <p>Attaching high-cardinality attributes to {@link Context} poses a critical risk to metrics.
+ * Synchronous metric recordings inherit these attributes into their metric point dimension sets,
+ * which can cause metric stream explosion and high memory consumption. Therefore, attributes
+ * associated with {@link Context} <b>must</b> be low-cardinality unless a filter is explicitly
+ * configured on the metric provider to exclude them.
+ *
+ * <h2>Bound Instruments</h2>
+ *
+ * <p>Bound instruments do not inherit dynamic context-scoped attributes. Their attribute sets are
+ * resolved once at bind time, and subsequent bound recording operations do not access or evaluate
+ * the active context.
+ */
+public final class ContextAttributes {
+
+  private static final ContextKey<Attributes> CONTEXT_ATTRIBUTES_KEY =
+      ContextKey.named("opentelemetry-context-attributes");
+
+  private ContextAttributes() {}
+
+  /**
+   * Sets the {@link Attributes} on the given {@link Context}, completely replacing any previously
+   * associated context-scoped attributes.
+   *
+   * @param context the context to attach attributes to. If null, {@link Context#root()} is
+   *     returned.
+   * @param attributes the authoritative attributes to associate. If null, {@code context} is
+   *     returned unchanged. Pass {@link Attributes#empty()} to logically clear context-scoped
+   *     attributes.
+   * @return a new context containing the specified attributes.
+   */
+  public static Context set(@Nullable Context context, @Nullable Attributes attributes) {
+    if (context == null) {
+      ApiUsageLogger.logNullParam(ContextAttributes.class, "set", "context");
+      return Context.root();
+    }
+    if (attributes == null) {
+      ApiUsageLogger.logNullParam(ContextAttributes.class, "set", "attributes");
+      return context;
+    }
+    if (attributes.isEmpty()) {
+      Attributes existing = context.get(CONTEXT_ATTRIBUTES_KEY);
+      if (existing == null || existing.isEmpty()) {
+        return context;
+      }
+      return context.with(CONTEXT_ATTRIBUTES_KEY, Attributes.empty());
+    }
+    return context.with(CONTEXT_ATTRIBUTES_KEY, attributes);
+  }
+
+  /**
+   * Adds the given {@link Attributes} to the {@link Context}, merging them with any existing
+   * context-scoped attributes. Conflicting keys take the value from {@code attributes}.
+   *
+   * @param context the context to attach attributes to. If null, {@link Context#root()} is
+   *     returned.
+   * @param attributes the attributes to add. If null or empty, {@code context} is returned
+   *     unchanged.
+   * @return a new context containing the merged attributes.
+   */
+  public static Context add(@Nullable Context context, @Nullable Attributes attributes) {
+    if (context == null) {
+      ApiUsageLogger.logNullParam(ContextAttributes.class, "add", "context");
+      return Context.root();
+    }
+    if (attributes == null) {
+      ApiUsageLogger.logNullParam(ContextAttributes.class, "add", "attributes");
+      return context;
+    }
+    if (attributes.isEmpty()) {
+      return context;
+    }
+    Attributes existing = get(context);
+    if (existing.isEmpty()) {
+      return set(context, attributes);
+    }
+    return set(context, existing.toBuilder().putAll(attributes).build());
+  }
+
+  /**
+   * Returns the {@link Attributes} associated with the given {@code context}, or {@link
+   * Attributes#empty()} if none are present.
+   *
+   * <p>This method is intended primarily for telemetry pipeline components such as SDKs, samplers,
+   * processors, and exporters. Application code should treat context-scoped attributes as
+   * write-only via {@link #set(Context, Attributes)} or {@link #add(Context, Attributes)}.
+   */
+  public static Attributes get(@Nullable Context context) {
+    if (context == null) {
+      return Attributes.empty();
+    }
+    Attributes attributes = context.get(CONTEXT_ATTRIBUTES_KEY);
+    return attributes != null ? attributes : Attributes.empty();
+  }
+}

api/incubator/src/test/java/io/opentelemetry/api/incubator/common/ContextAttributesTest.java

@@ -0,0 +1,122 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.api.incubator.common;
+
+import static io.opentelemetry.api.common.AttributeKey.longKey;
+import static io.opentelemetry.api.common.AttributeKey.stringKey;
+import static org.assertj.core.api.Assertions.assertThat;
+
+import io.opentelemetry.api.common.Attributes;
+import io.opentelemetry.context.Context;
+import io.opentelemetry.context.Scope;
+import org.junit.jupiter.api.Test;
+
+class ContextAttributesTest {
+
+  @Test
+  void emptyContext_returnsEmptyAttributes() {
+    assertThat(ContextAttributes.get(Context.root())).isEqualTo(Attributes.empty());
+    assertThat(ContextAttributes.get(null)).isEqualTo(Attributes.empty());
+  }
+
+  @Test
+  void addNullValidation() {
+    Context root = Context.root();
+    Attributes attrs = Attributes.of(stringKey("k"), "v");
+    assertThat(ContextAttributes.add(null, attrs)).isEqualTo(Context.root());
+    assertThat(ContextAttributes.add(root, null)).isSameAs(root);
+  }
+
+  @Test
+  void addEmptyAttributes_returnsSameContext() {
+    Context root = Context.root();
+    assertThat(ContextAttributes.add(root, Attributes.empty())).isSameAs(root);
+  }
+
+  @Test
+  void setNullValidation() {
+    Context root = Context.root();
+    Attributes attrs = Attributes.of(stringKey("k"), "v");
+    assertThat(ContextAttributes.set(null, attrs)).isEqualTo(Context.root());
+    assertThat(ContextAttributes.set(root, null)).isSameAs(root);
+  }
+
+  @Test
+  void setReplacesExistingAndClearsWithEmpty() {
+    Context ctx1 =
+        ContextAttributes.set(
+            Context.root(), Attributes.of(stringKey("k1"), "v1", longKey("k2"), 2L));
+    assertThat(ContextAttributes.get(ctx1))
+        .isEqualTo(Attributes.of(stringKey("k1"), "v1", longKey("k2"), 2L));
+
+    // set() completely replaces previous attributes
+    Context ctx2 = ContextAttributes.set(ctx1, Attributes.of(stringKey("k3"), "v3"));
+    assertThat(ContextAttributes.get(ctx2)).isEqualTo(Attributes.of(stringKey("k3"), "v3"));
+
+    // set() with empty clears attributes
+    Context ctxCleared = ContextAttributes.set(ctx2, Attributes.empty());
+    assertThat(ContextAttributes.get(ctxCleared)).isEqualTo(Attributes.empty());
+
+    // set() with empty on already empty returns same context
+    assertThat(ContextAttributes.set(Context.root(), Attributes.empty())).isSameAs(Context.root());
+  }
+
+  @Test
+  void addAndGet_singleLayer() {
+    Attributes attrs = Attributes.of(stringKey("user.id"), "u123", longKey("retry"), 1L);
+    Context ctx = ContextAttributes.add(Context.root(), attrs);
+
+    assertThat(ContextAttributes.get(ctx)).isEqualTo(attrs);
+    assertThat(ContextAttributes.get(Context.root())).isEqualTo(Attributes.empty());
+  }
+
+  @Test
+  void addAndGet_nestedContextsMergeAndOverride() {
+    Context outer =
+        ContextAttributes.add(
+            Context.root(), Attributes.of(stringKey("k1"), "v1", stringKey("k2"), "v2"));
+    Context inner =
+        ContextAttributes.add(
+            outer, Attributes.of(stringKey("k2"), "v2-override", stringKey("k3"), "v3"));
+
+    assertThat(ContextAttributes.get(outer))
+        .isEqualTo(Attributes.of(stringKey("k1"), "v1", stringKey("k2"), "v2"));
+    assertThat(ContextAttributes.get(inner))
+        .isEqualTo(
+            Attributes.of(
+                stringKey("k1"), "v1", stringKey("k2"), "v2-override", stringKey("k3"), "v3"));
+  }
+
+  @Test
+  void addWithSameNameDifferentType_overwritesExisting() {
+    Context ctx1 =
+        ContextAttributes.add(Context.root(), Attributes.of(stringKey("foo"), "stringVal"));
+    Context ctx2 = ContextAttributes.add(ctx1, Attributes.of(longKey("foo"), 42L));
+    assertThat(ContextAttributes.get(ctx2)).isEqualTo(Attributes.of(longKey("foo"), 42L));
+  }
+
+  @Test
+  void scopeAttachment_restoresOuterContextAttributesOnClose() {
+    Context outer = ContextAttributes.add(Context.root(), Attributes.of(stringKey("env"), "prod"));
+    try (Scope ignoredOuter = outer.makeCurrent()) {
+      assertThat(ContextAttributes.get(Context.current()))
+          .isEqualTo(Attributes.of(stringKey("env"), "prod"));
+
+      Context inner =
+          ContextAttributes.add(
+              Context.current(),
+              Attributes.of(stringKey("env"), "staging", stringKey("req"), "r1"));
+      try (Scope ignoredInner = inner.makeCurrent()) {
+        assertThat(ContextAttributes.get(Context.current()))
+            .isEqualTo(Attributes.of(stringKey("env"), "staging", stringKey("req"), "r1"));
+      }
+
+      assertThat(ContextAttributes.get(Context.current()))
+          .isEqualTo(Attributes.of(stringKey("env"), "prod"));
+    }
+    assertThat(ContextAttributes.get(Context.current())).isEqualTo(Attributes.empty());
+  }
+}

sdk/common/src/main/java/io/opentelemetry/sdk/common/internal/AttributesMap.java

@@ -180,6 +180,17 @@ public <T> T get(AttributeKey<T> key) {
     return (T) entryValues[idx];
   }
 
+  /**
+   * Returns whether an attribute with the given key name exists in this map, regardless of type.
+   *
+   * <p>Runs with expected/amortized O(1) complexity using the internal open-addressing table.
+   *
+   * @param key the attribute key name to look up. Must not be null.
+   */
+  public boolean containsKey(String key) {
+    return hashTable[findSlot(key)] != EMPTY;
+  }
+
   @Override
   public int size() {
     return size;

sdk/common/src/test/java/io/opentelemetry/sdk/common/internal/AttributesMapTest.java

@@ -109,6 +109,26 @@ void get_returnsNullForAbsentKey() {
     assertThat(map.get(stringKey("absent"))).isNull();
   }
 
+  // ---- containsKey ----
+
+  @Test
+  void containsKey_returnsTrueForPresentKey() {
+    AttributesMap map = AttributesMap.create(10, Integer.MAX_VALUE);
+    map.put(stringKey("k"), "v");
+
+    assertThat(map.containsKey("k")).isTrue();
+    assertThat(map.containsKey("absent")).isFalse();
+  }
+
+  @Test
+  void containsKey_returnsTrueForSameNameDifferentType() {
+    AttributesMap map = AttributesMap.create(10, Integer.MAX_VALUE);
+    map.put(longKey("count"), 42L);
+
+    // containsKey() is name-based: true even if originally put as longKey("count")
+    assertThat(map.containsKey("count")).isTrue();
+  }
+
   // ---- capacity ----
 
   @Test

sdk/logs/src/main/java/io/opentelemetry/sdk/logs/IncubatingUtil.java

@@ -5,6 +5,9 @@
 
 package io.opentelemetry.sdk.logs;
 
+import io.opentelemetry.api.common.Attributes;
+import io.opentelemetry.api.incubator.common.ContextAttributes;
+import io.opentelemetry.context.Context;
 import io.opentelemetry.sdk.common.InstrumentationScopeInfo;
 import io.opentelemetry.sdk.logs.internal.LoggerConfig;
 
@@ -30,4 +33,8 @@ static SdkLogRecordBuilder createExtendedLogRecordBuilder(
       SdkLogger logger) {
     return new ExtendedSdkLogRecordBuilder(loggerSharedState, instrumentationScopeInfo, logger);
   }
+
+  static Attributes getContextAttributes(Context context) {
+    return ContextAttributes.get(context);
+  }
 }

sdk/logs/src/main/java/io/opentelemetry/sdk/logs/LoggerSharedState.java

@@ -5,11 +5,14 @@
 
 package io.opentelemetry.sdk.logs;
 
+import io.opentelemetry.api.common.AttributeKey;
 import io.opentelemetry.sdk.common.Clock;
 import io.opentelemetry.sdk.common.CompletableResultCode;
+import io.opentelemetry.sdk.common.InstrumentationScopeInfo;
 import io.opentelemetry.sdk.common.internal.ExceptionAttributeResolver;
 import io.opentelemetry.sdk.resources.Resource;
 import io.opentelemetry.sdk.resources.internal.SdkResourceProvider;
+import java.util.function.BiPredicate;
 import java.util.function.Supplier;
 import javax.annotation.Nullable;
 
@@ -25,6 +28,11 @@ final class LoggerSharedState {
   private final Clock clock;
   private final ExceptionAttributeResolver exceptionAttributeResolver;
   private final SdkLoggerInstrumentation loggerInstrumentation;
+
+  @Nullable
+  private final BiPredicate<InstrumentationScopeInfo, AttributeKey<?>>
+      contextScopedAttributesFilter;
+
   @Nullable private volatile CompletableResultCode shutdownResult = null;
 
   LoggerSharedState(
@@ -33,13 +41,16 @@ final class LoggerSharedState {
       LogRecordProcessor logRecordProcessor,
       Clock clock,
       ExceptionAttributeResolver exceptionAttributeResolver,
-      SdkLoggerInstrumentation loggerInstrumentation) {
+      SdkLoggerInstrumentation loggerInstrumentation,
+      @Nullable
+          BiPredicate<InstrumentationScopeInfo, AttributeKey<?>> contextScopedAttributesFilter) {
     this.resourceProvider = resourceProvider;
     this.logLimitsSupplier = logLimitsSupplier;
     this.logRecordProcessor = logRecordProcessor;
     this.clock = clock;
     this.exceptionAttributeResolver = exceptionAttributeResolver;
     this.loggerInstrumentation = loggerInstrumentation;
+    this.contextScopedAttributesFilter = contextScopedAttributesFilter;
   }
 
   Resource getResource() {
@@ -66,6 +77,11 @@ SdkLoggerInstrumentation getLoggerInstrumentation() {
     return loggerInstrumentation;
   }
 
+  @Nullable
+  BiPredicate<InstrumentationScopeInfo, AttributeKey<?>> getContextScopedAttributesFilter() {
+    return contextScopedAttributesFilter;
+  }
+
   boolean hasBeenShutdown() {
     return shutdownResult != null;
   }