add APIs for llm obs

Author: gary-huang

dd-trace-api/src/main/java/datadog/trace/api/llmobs/LLMObs.java

@@ -0,0 +1,56 @@
+package datadog.trace.api.llmobs;
+
+import datadog.trace.api.llmobs.noop.NoOpLLMObsSpan;
+import javax.annotation.Nullable;
+
+public class LLMObs {
+
+
+  public static LLMObsSpan startLLMSpan(
+      String modelName, String name, @Nullable String modelProvider, @Nullable String sessionID, @Nullable String mlApp) {
+
+    return NoOpLLMObsSpan.INSTANCE;
+  }
+
+  public static LLMObsSpan startAgentSpan(
+      String name, @Nullable String sessionID, @Nullable String mlApp) {
+
+    return NoOpLLMObsSpan.INSTANCE;
+  }
+
+  public static LLMObsSpan startToolSpan(
+      String name, @Nullable String sessionID, @Nullable String mlApp) {
+
+    return NoOpLLMObsSpan.INSTANCE;
+  }
+
+  public static LLMObsSpan startTaskSpan(
+      String name, @Nullable String sessionID, @Nullable String mlApp) {
+
+    return NoOpLLMObsSpan.INSTANCE;
+  }
+
+  public static LLMObsSpan startWorkflowSpan(
+      String name, @Nullable String sessionID, @Nullable String mlApp) {
+
+    return NoOpLLMObsSpan.INSTANCE;
+  }
+
+  public interface LLMObsSpanFactory {
+    LLMObsSpan startLLMSpan(String modelName, String name, @Nullable String modelProvider, @Nullable String sessionID, @Nullable String mlApp);
+    LLMObsSpan startAgentSpan(String name, @Nullable String sessionID, @Nullable String mlApp);
+    LLMObsSpan startToolSpan(String name, @Nullable String sessionID, @Nullable String mlApp);
+    LLMObsSpan startTaskSpan(String name, @Nullable String sessionID, @Nullable String mlApp);
+    LLMObsSpan startWorkflowSpan(String name, @Nullable String sessionID, @Nullable String mlApp);
+  }
+
+  private class NoOpLLMObsSpanFactory implements LLMObsSpanFactory{
+    public LLMObsSpan startLLMSpan(String modelName, String name, @Nullable String modelProvider, @Nullable String sessionID, @Nullable String mlApp) {
+      return NoOpLLMObsSpan.INSTANCE;
+    }
+    public LLMObsSpan startAgentSpan(String name, @Nullable String sessionID, @Nullable String mlApp);
+    LLMObsSpan startToolSpan(String name, @Nullable String sessionID, @Nullable String mlApp);
+    LLMObsSpan startTaskSpan(String name, @Nullable String sessionID, @Nullable String mlApp);
+    LLMObsSpan startWorkflowSpan(String name, @Nullable String sessionID, @Nullable String mlApp);
+  }
+}

dd-trace-api/src/main/java/datadog/trace/api/llmobs/LLMObsSpan.java

@@ -0,0 +1,15 @@
+package datadog.trace.api.llmobs;
+
+/**
+ * This interface represent an individual LLM Obs span.
+ */
+public interface LLMObsSpan {
+
+  /**
+   * Annotate spans with inputs, outputs, and metadata.
+   *
+   * @param key The name of the tag
+   * @param value The value of the tag
+   */
+  void annotate(String key, Object value);
+}

dd-trace-api/src/main/java/datadog/trace/api/llmobs/noop/NoOpLLMObsSpan.java

@@ -0,0 +1,10 @@
+package datadog.trace.api.llmobs.noop;
+
+import datadog.trace.api.llmobs.LLMObsSpan;
+
+public class NoOpLLMObsSpan implements LLMObsSpan {
+  public static final LLMObsSpan INSTANCE = new NoOpLLMObsSpan();
+
+  @Override
+  public void annotate(String key, Object value) {}
+}