Add session.list_devices() API

In order to debug a TensorFlow cluster or check whether devices are available
in a local session (e.g. GPU drivers are loaded), this change adds a
`sess.list_devices` API to list all devices within the cluster.

This CL implements the list_devices() feature via extensions to the TensorFlow
C API, and the corresponding additions to the session.h session class and
corresponding subclasses for both direct sessions, grpc_sessions,
tensorflow_serving, and others.

Additionally, in order to accomidate ClusterSpec propagation clusters,
Master::ListDevices now also includes a session_handle in order to identify
the appropriate master_session on which it should list the available
devices. (With ClusterSpec propagation, different sessions can have different
servers with different device capabilities.)

This CL adds a ListDevices() API to MasterSession. It is most
efficient to implement this API call there, because the MasterSession
already has a list of devices.

Additionally, this change upgrades the implementation of
Master::ListDevices() to delegate to the MasterSession if a session
handle is specified, and to return an error if no corresponding session
is found.
PiperOrigin-RevId: 157239656

1 files changed, 4 insertions, 1 deletions

diff --git a/tensorflow/c/c_api_internal.h b/tensorflow/c/c_api_internal.h
index b5320d20da..f17ac26ad9 100644
--- a/tensorflow/c/c_api_internal.h
+++ b/tensorflow/c/c_api_internal.h
@@ -29,7 +29,6 @@ limitations under the License.
 #include "tensorflow/core/platform/types.h"
 #include "tensorflow/core/common_runtime/shape_refiner.h"
 
-
 // Internal structures used by the C API. These are likely to change and should
 // not be depended on.
 
@@ -114,3 +113,7 @@ struct TF_Session {
 struct TF_ImportGraphDefOptions {
   tensorflow::ImportGraphDefOptions opts;
 };
+
+struct TF_DeviceList {
+  std::vector<tensorflow::DeviceAttributes> response;
+};