tensorflow::uint64 send_device_incarnation);

// Return a RecvOp op `op_name` with the attributes `send_device`,
// `recv_device`, and `send_device_incarnation` set.
TFE_Op* RecvOp(TFE_Context* ctx, const std::string& op_name,
               const std::string& send_device, const std::string& recv_device,
               tensorflow::uint64 send_device_incarnation);

// reinitialized (e.g. cleared caches) as well.
TF_CAPI_EXPORT extern uint64_t TFE_GetContextId(TFE_Context* ctx);

// -----------------------------------------------------------------------------
// Cancellation APIs.

typedef struct TFE_CancellationManager TFE_CancellationManager;
typedef int64_t TFE_CancellationToken;
typedef struct TFE_CancelCallback {
  void (*callback)(void* context);

  Status DeleteFile(const std::string& fname, TransactionToken* token) override;
  Status DeleteRecursively(const std::string& dirname, TransactionToken* token,
                           int64_t* undeleted_files,
                           int64_t* undeleted_dirs) override;
  Status DeleteDir(const std::string& dirname,
                   TransactionToken* token) override;
  Status RecursivelyCreateDir(const std::string& dirname,

// and -1 will be returned.
TF_CAPI_EXPORT extern int64_t TF_DeviceListMemoryBytes(
    const TF_DeviceList* list, int index, TF_Status* status);

// Retrieve the incarnation number of a given device.
//
// If index is out of bounds, an error code will be set in the status object,
// and 0 will be returned.
TF_CAPI_EXPORT extern uint64_t TF_DeviceListIncarnation(

  // Get a list of the names of functions that have been registered.
  virtual std::vector<string> ListFunctionNames() = 0;

  struct CacheStats {
    int64_t kernel_cache_size;
    int64_t device_cache_size;
    std::map<std::string, int64_t> func_kernel_cache_entries;
    int64_t local_rendezvous_cache_active_size;
  };
  virtual CacheStats GetCacheStats() = 0;

  // Map from tensor ID to how many references still exist for this tensor in
  // the tape.
  std::unordered_map<int64_t, int64_t> tensor_usage_counts;

  // Maps from op ID to how many output tensors of this op still need to have
  // their gradients computed.
  std::unordered_map<int64_t, int64_t> op_missing_tensor;
};

// If `persistent_tape` is true, op_tape is not changed and none of the

  // `keep_alive_secs` of inactivity.
  virtual Status SetOrUpdateServerDef(const ServerDef& server_def,
                                      bool reset_context, int keep_alive_secs,
                                      int64_t init_timeout_in_ms, int retries,
                                      bool clear_existing_contexts = false) = 0;

  // Initializes context for the local worker and no contexts will be created

// nullptr will be returned.
TF_CAPI_EXPORT extern TF_Buffer* TF_CoordinationServiceGetKeyValue(
    const char* key, int64_t key_size, TF_CoordinationServiceAgent* agent,
    TF_Status* status);

TF_CAPI_EXPORT extern TF_Buffer* TF_CoordinationServiceGetKeyValueWithTimeout(
    const char* key, int64_t key_size, int64_t timeout_seconds,
    TF_CoordinationServiceAgent* agent, TF_Status* status);

// Return a tensor handle with given type, values and dimensions.
template <class T, TF_DataType datatype>
Status TestTensorHandleWithDims(AbstractContext* ctx, const T* data,
                                const int64_t* dims, int num_dims,
                                AbstractTensorHandle** tensor) {
  std::unique_ptr<TF_Status, decltype(&TF_DeleteStatus)> status(
      TF_NewStatus(), TF_DeleteStatus);
  TFE_Context* eager_ctx =