/* Copyright 2015 The TensorFlow Authors. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
==============================================================================*/

#ifndef TENSORFLOW_CORE_COMMON_RUNTIME_SESSION_FACTORY_H_
#define TENSORFLOW_CORE_COMMON_RUNTIME_SESSION_FACTORY_H_

#include <string>

#include "tensorflow/core/lib/core/errors.h"
#include "tensorflow/core/lib/core/status.h"
#include "tensorflow/core/lib/gtl/array_slice.h"
#include "tensorflow/core/platform/types.h"

namespace tensorflow {

class Session;
struct SessionOptions;

class SessionFactory {
 public:
  // Creates a new session and stores it in *out_session, or fails with an error
  // status if the Session could not be created. Caller takes ownership of
  // *out_session if this returns OkStatus().
  virtual absl::Status NewSession(const SessionOptions& options,
                                  Session** out_session) = 0;

  virtual bool AcceptsOptions(const SessionOptions& options) = 0;

  // Abort and close all existing sessions, disconnecting their resources from
  // future sessions.
  //
  // Reset() allows misbehaving or slow sessions to be aborted and closed, and
  // causes their resources eventually to be released.  Reset() does not wait
  // for the computations in old sessions to cease; it merely starts the
  // process of tearing them down.  However, if a new session is started after
  // a Reset(), the new session is isolated from changes that old sessions
  // (started prior to the Reset()) may continue to make to resources, provided
  // all those resources are in containers listed in "containers".
  //
  // Old sessions may continue to have side-effects on resources not in
  // containers listed in "containers", and thus may affect future
  // sessions' results in ways that are hard to predict.  Thus, if well-defined
  // behavior is desired, is it recommended that all containers be listed in
  // "containers".
  //
  // If the "containers" vector is empty, the default container is assumed.
  // If the "containers" vector is non-empty, the default container should be
  // listed explicitly.
  //
  // Sessions that support resource containers should override this function.
  virtual absl::Status Reset(const SessionOptions& options,
                             const std::vector<string>& containers) {
    return errors::Unimplemented("Reset()");
  }

  virtual ~SessionFactory() {}
  static void Register(const string& runtime_type, SessionFactory* factory);
  static absl::Status GetFactory(const SessionOptions& options,
                                 SessionFactory** out_factory);
};

}  // namespace tensorflow

#endif  // TENSORFLOW_CORE_COMMON_RUNTIME_SESSION_FACTORY_H_
