test(profiling): AgentPhase tag visible on CPU execution samples

ddprof-test/src/test/java/com/datadoghq/profiler/llm/AgentPhaseProfilingTest.java

@@ -0,0 +1,79 @@
+package com.datadoghq.profiler.llm;
+
+import com.datadoghq.profiler.AbstractProfilerTest;
+import com.datadoghq.profiler.AgentPhase;
+import com.datadoghq.profiler.ContextSetter;
+import com.datadoghq.profiler.Platform;
+import org.junit.jupiter.api.Assumptions;
+import org.junit.jupiter.api.Test;
+import org.openjdk.jmc.common.item.IAttribute;
+import org.openjdk.jmc.common.item.IItem;
+import org.openjdk.jmc.common.item.IItemCollection;
+import org.openjdk.jmc.common.item.IItemIterable;
+import org.openjdk.jmc.common.item.IMemberAccessor;
+
+import java.util.Arrays;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.openjdk.jmc.common.item.Attribute.attr;
+import static org.openjdk.jmc.common.unit.UnitLookup.PLAIN_TEXT;
+
+public class AgentPhaseProfilingTest extends AbstractProfilerTest {
+
+    @Override
+    protected String getProfilerCommand() {
+        return "cpu=10ms,attributes=" + AgentPhase.ATTRIBUTE_NAME;
+    }
+
+    private static final IAttribute<String> AGENT_PHASE = attr(
+            AgentPhase.ATTRIBUTE_NAME, AgentPhase.ATTRIBUTE_NAME, AgentPhase.ATTRIBUTE_NAME, PLAIN_TEXT);
+
+    @Test
+    public void cpuSamplesCarryAgentPhase() throws Exception {
+        Assumptions.assumeTrue(!Platform.isJ9());
+        registerCurrentThreadForWallClockProfiling();
+
+        ContextSetter cs = new ContextSetter(profiler,
+                Arrays.asList(AgentPhase.ATTRIBUTE_NAME));
+        int offset = cs.offsetOf(AgentPhase.ATTRIBUTE_NAME);
+        assertTrue(offset >= 0, "llm.agent.phase must have a valid slot index");
+
+        AtomicBoolean done = new AtomicBoolean(false);
+        Thread worker = new Thread(() -> {
+            cs.setContextValue(offset, AgentPhase.AWAITING_INFERENCE.token());
+            long sum = 0;
+            while (!done.get()) {
+                sum += sum + 1;
+            }
+            cs.clearContextValue(offset);
+        });
+        worker.setDaemon(true);
+        worker.start();
+        Thread.sleep(300);
+        done.set(true);
+        worker.join();
+
+        stopProfiler();
+
+        IItemCollection events = verifyEvents("datadog.ExecutionSample");
+        boolean found = false;
+        outer:
+        for (IItemIterable iterable : events) {
+            IMemberAccessor<String, IItem> phaseAccessor = AGENT_PHASE.getAccessor(iterable.getType());
+            if (phaseAccessor == null) continue;
+            for (IItem item : iterable) {
+                String val = phaseAccessor.getMember(item);
+                if (AgentPhase.AWAITING_INFERENCE.token().equals(val)) {
+                    found = true;
+                    break outer;
+                }
+            }
+        }
+        assertTrue(found, "Expected at least one ExecutionSample with "
+                + AgentPhase.ATTRIBUTE_NAME + "=" + AgentPhase.AWAITING_INFERENCE.token()
+                + " — if the test fails, check that the JMC accessor name '" + AgentPhase.ATTRIBUTE_NAME + "' "
+                + "matches the field name emitted by the profiler (inspect the JFR: "
+                + "jfr print --events datadog.ExecutionSample <recording.jfr>)");
+    }
+}