// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you 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 __MESOS_SLAVE_RESOURCE_ESTIMATOR_HPP__
#define __MESOS_SLAVE_RESOURCE_ESTIMATOR_HPP__

#include <string>

#include <mesos/resources.hpp>

#include <process/future.hpp>

#include <stout/lambda.hpp>
#include <stout/nothing.hpp>
#include <stout/option.hpp>
#include <stout/try.hpp>

namespace mesos {
namespace slave {

// A slave component used for oversubscription. It estimates and
// predicts the total resources used on the slave and informs the
// master about resources that can be oversubscribed.
class ResourceEstimator
{
public:
  // Create a resource estimator instance of the given type specified
  // by the user. If the type is not specified, a default resource
  // estimator instance will be created.
  static Try<ResourceEstimator*> create(const Option<std::string>& type);

  virtual ~ResourceEstimator() {}

  // Initializes this resource estimator. This method needs to be
  // called before any other member method is called. It registers
  // a callback in the resource estimator. The callback allows the
  // resource estimator to fetch the current resource usage for each
  // executor on slave.
  virtual Try<Nothing> initialize(
      const lambda::function<process::Future<ResourceUsage>()>& usage) = 0;

  // Returns the current estimation about the *maximum* amount of
  // resources that can be oversubscribed on the slave. A new
  // estimation will invalidate all the previously returned
  // estimations. The slave will be calling this method periodically
  // to forward it to the master. As a result, the estimator should
  // respond with an estimate every time this method is called.
  virtual process::Future<Resources> oversubscribable() = 0;
};

} // namespace slave {
} // namespace mesos {

#endif // __MESOS_SLAVE_RESOURCE_ESTIMATOR_HPP__