// 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_CONTAINER_LOGGER_HPP__
#define __MESOS_SLAVE_CONTAINER_LOGGER_HPP__

#include <map>
#include <string>
#include <vector>

#include <mesos/mesos.hpp>

#include <mesos/slave/containerizer.hpp>

#include <process/future.hpp>
#include <process/subprocess.hpp>
#include <process/shared.hpp>

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

namespace mesos {
namespace slave {

/**
 * A containerizer component used to manage container logs.
 *
 * The `ContainerLogger` is responsible for handling the stdout/stderr of
 * containers.
 *
 * The container logger is also responsible for providing a public interface for
 * retrieving the logs.
 *
 * Care should be taken when implementing stateful container loggers: the logger
 * should be capable of recovering its state and its managed containers during
 * the agent recovery process in absence of such interface methods as
 * `ContainerLogger::recover()` and `ContainerLogger::cleanup()`.
 *
 * The lack of `ContainerLogger::cleanup()` or similar prevents synchronization
 * on container termination, i.e., delaying sending a terminal status update for
 * the container until the logger reports completion.
 *
 * TODO(josephw): Provide an interface for exposing custom log-retrieval
 * endpoints via the Mesos web UI.
 */
class ContainerLogger
{
public:
  /**
   * Create and initialize a container logger instance of the given type,
   * specified by the `container_logger` agent flag.  If the type is not
   * specified, a default container logger instance will be created.
   *
   * See `ContainerLogger::initialize`.
   */
  static Try<ContainerLogger*> create(const Option<std::string>& type);

  virtual ~ContainerLogger() {}

  /**
   * Initializes this container logger.  This method must be called before any
   * other member function is called.
   *
   * The container logger module should return an error if the particular
   * module is not supported.  For example, if the module implements log
   * rotation via the `logrotate` utility, the module can return an error if
   * the utility is not found.
   */
  virtual Try<Nothing> initialize() = 0;

  /**
   * Called before Mesos creates a container.
   *
   * The container logger is given some of the arguments which the containerizer
   * will use to launch a container.  The container logger should return a
   * `ContainerIO` which tells the containerizer how to handle the stdout
   * and stderr of the container.  The container logger can modify the fields
   * within the `ContainerIO` as much as necessary, with some exceptions;
   * see the struct `ContainerIO` above.
   *
   * The container logger should not lose stdout/stderr if the agent fails over.
   *
   * @param containerId The ID of the container.
   * @param containerConfig The configurations of the container, including the
   *     ExecutorInfo (if applied), as well as the absolute path to the sandbox
   *     directory of the container. The sandbox path is provided in case
   *     the container logger needs to store files in the container's sandbox,
   *     such as persistent state between agent failovers.  NOTE: All files in
   *     the sandbox are exposed via the `/files` endpoint.
   */
  virtual process::Future<ContainerIO> prepare(
      const ContainerID& containerId,
      const ContainerConfig& containerConfig) = 0;
};

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

#endif // __MESOS_SLAVE_CONTAINER_LOGGER_HPP__