Save an empty event file when StartTracing is called.

This is to help with TensorBoard subdirectory searching.

PiperOrigin-RevId: 236260947

tensorflow/core/profiler/rpc/client/BUILD

@@ -15,7 +15,7 @@ tf_cuda_library(
     deps = [
         ":dump_tpu_profile",
         "//tensorflow:grpc++",
-        "//tensorflow/core:framework_internal",
+        "//tensorflow/core:framework",
         "//tensorflow/core:grpc_services",
         "//tensorflow/core:lib",
         "//tensorflow/core/distributed_runtime/rpc:grpc_util",

tensorflow/core/profiler/rpc/client/capture_profile.cc

@@ -28,6 +28,7 @@ limitations under the License.
 #include "tensorflow/core/lib/strings/str_util.h"
 #include "tensorflow/core/platform/grpc_services.h"
 #include "tensorflow/core/profiler/rpc/client/dump_tpu_profile.h"
+#include "tensorflow/core/util/events_writer.h"
 
 namespace tensorflow {
 namespace profiler {
@@ -162,6 +163,22 @@ Status NewSession(const string& service_addr,
   return Status::OK();
 }
 
+// Creates an empty event file if not already exists, which indicates that we
+// have a profile/plugin/ directory in the current logdir.
+Status MaybeCreateEmptyEventFile(const tensorflow::string& logdir) {
+  // Suffix for an empty event file.
+  constexpr char kProfileEmptySuffix[] = ".profile-empty";
+  std::vector<string> children;
+  TF_RETURN_IF_ERROR(Env::Default()->GetChildren(logdir, &children));
+  for (const string& child : children) {
+    if (str_util::EndsWith(child, kProfileEmptySuffix)) {
+      return Status::OK();
+    }
+  }
+  EventsWriter event_writer(io::JoinPath(logdir, "events"));
+  return event_writer.InitWithSuffix(kProfileEmptySuffix);
+}
+
 // Starts tracing on a single or multiple TPU hosts and saves the result in the
 // given logdir. If no trace was collected, retries tracing for
 // num_tracing_attempts.
@@ -178,6 +195,8 @@ Status StartTracing(const tensorflow::string& service_addr,
   std::vector<tensorflow::string> hostnames =
       tensorflow::str_util::Split(workers_list, ",");
 
+  TF_RETURN_IF_ERROR(MaybeCreateEmptyEventFile(logdir));
+
   Status status = Status::OK();
   int remaining_attempts = num_tracing_attempts;
   tensorflow::ProfileOptions opts;
@@ -248,4 +267,3 @@ void StartMonitoring(const tensorflow::string& service_addr, int duration_ms,
 }  // namespace client
 }  // namespace profiler
 }  // namespace tensorflow
-