Improve Jaeger Python traces (more spans/snapshot tag).

src/pyodide/internal/python.js

@@ -86,7 +86,7 @@ export async function uploadArtifacts() {
  * Used for tracing via Jaeger.
  */
 
-export async function enterJaegerSpan(span, callback) {
+export function enterJaegerSpan(span, callback) {
   if (!internalJaeger.traceId) {
     // Jaeger tracing not enabled or traceId is not present in request.
     return callback();

src/pyodide/python-entrypoint-helper.js

@@ -137,15 +137,17 @@ function getPyodide() {
 
 let mainModulePromise;
 function getMainModule() {
-  if (mainModulePromise) {
+  return enterJaegerSpan("get_main_module", async () => {
+    if (mainModulePromise) {
+      return mainModulePromise;
+    }
+    mainModulePromise = (async function () {
+      const pyodide = await getPyodide();
+      await setupPackages(pyodide);
+      return enterJaegerSpan("pyimport_main_module", () => pyimportMainModule(pyodide));
+    })();
     return mainModulePromise;
-  }
-  mainModulePromise = (async function () {
-    const pyodide = await getPyodide();
-    await setupPackages(pyodide);
-    return pyimportMainModule(pyodide);
-  })();
-  return mainModulePromise;
+  });
 }
 
 // Do not setup anything to do with Python in the global scope when tracing. The Jaeger tracing

src/workerd/api/pyodide/pyodide.h

@@ -134,6 +134,10 @@ class ArtifactBundler : public jsg::Object {
     return uploadMemorySnapshotCb != kj::none;
   }
 
+  bool hasMemorySnapshot() {
+    return existingSnapshot != kj::none;
+  }
+
   static jsg::Ref<ArtifactBundler> makeDisabledBundler() {
     return jsg::alloc<ArtifactBundler>();
   }