multi projec tracing

Author: ankrgyl

.changeset/multi-project-parent-span.md

@@ -0,0 +1,5 @@
+---
+"braintrust": patch
+---
+
+Allow spans started with an exported parent to write to the receiver object while preserving trace lineage.

js/src/logger.test.ts

@@ -2429,6 +2429,68 @@ describe("parent precedence", () => {
     expect(byName.forced.span_parents).toContain(byName.outer.span_id);
     expect(byName.forced.span_parents).not.toContain(byName.inner.span_id);
   });
+
+  test("logger.startSpan with exported parent uses receiver project", async () => {
+    const primaryLogger = initLogger({
+      projectName: "primary",
+      projectId: "project-a",
+    });
+    const secondaryLogger = initLogger({
+      projectName: "secondary",
+      projectId: "project-b",
+    });
+
+    const root = primaryLogger.startSpan({ name: "root" });
+    const parentStr = await root.export();
+    root.end();
+
+    const child = secondaryLogger.startSpan({
+      name: "child",
+      parent: parentStr,
+    });
+    child.end();
+
+    await memory.flush();
+    const events = await memory.drain();
+    const byName: any = Object.fromEntries(
+      events.map((e: any) => [e.span_attributes?.name, e]),
+    );
+
+    expect(byName.child.project_id).toBe("project-b");
+    expect(byName.child.root_span_id).toBe(byName.root.root_span_id);
+    expect(byName.child.span_parents).toContain(byName.root.span_id);
+  });
+
+  test("experiment.startSpan with exported parent uses receiver experiment", async () => {
+    const primaryExperiment = _exportsForTestingOnly.initTestExperiment(
+      "experiment-a",
+      "project-a",
+    );
+    const secondaryExperiment = _exportsForTestingOnly.initTestExperiment(
+      "experiment-b",
+      "project-b",
+    );
+
+    const root = primaryExperiment.startSpan({ name: "root" });
+    const parentStr = await root.export();
+    root.end();
+
+    const child = secondaryExperiment.startSpan({
+      name: "child",
+      parent: parentStr,
+    });
+    child.end();
+
+    await memory.flush();
+    const events = await memory.drain();
+    const byName: any = Object.fromEntries(
+      events.map((e: any) => [e.span_attributes?.name, e]),
+    );
+
+    expect(byName.child.experiment_id).toBe("experiment-b");
+    expect(byName.child.root_span_id).toBe(byName.root.root_span_id);
+    expect(byName.child.span_parents).toContain(byName.root.span_id);
+  });
 });
 
 test("attachment with unreadable path logs warning", () => {

js/src/logger.ts

@@ -2236,20 +2236,7 @@ function startSpanParentArgs(args: {
       );
     }
 
-    const parentComponentsObjectIdLambda = spanComponentsToObjectIdLambda(
-      args.state,
-      parentComponents,
-    );
-    const computeParentObjectId = async () => {
-      const parentComponentsObjectId = await parentComponentsObjectIdLambda();
-      if ((await args.parentObjectId.get()) !== parentComponentsObjectId) {
-        throw new Error(
-          `Mismatch between expected span parent object id ${await args.parentObjectId.get()} and provided id ${parentComponentsObjectId}`,
-        );
-      }
-      return await args.parentObjectId.get();
-    };
-    argParentObjectId = new LazyValue(computeParentObjectId);
+    argParentObjectId = args.parentObjectId;
     if (parentComponents.data.row_id) {
       argParentSpanIds = {
         spanId: parentComponents.data.span_id,