text: /**
   *    Copyright (C) 2017 MongoDB Inc.
   *
   *    This program is free software: you can redistribute it and/or  modify
   *    it under the terms of the GNU Affero General Public License, version 3,
   *    as published by the Free Software Foundation.
   *
   *    This program is distributed in the hope that it will be useful,
   *    but WITHOUT ANY WARRANTY; without even the implied warranty of
   *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   *    GNU Affero General Public License for more details.
   *
   *    You should have received a copy of the GNU Affero General Public License
   *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
   *
   *    As a special exception, the copyright holders give permission to link the
   *    code of portions of this program with the OpenSSL library under certain
   *    conditions as described in each individual source file and distribute
   *    linked combinations including the program with the OpenSSL library. You
   *    must comply with the GNU Affero General Public License in all respects for
   *    all of the code used other than as permitted herein. If you modify file(s)
   *    with this exception, you may extend this exception to your version of the
   *    file(s), but you are not obligated to do so. If you do not wish to do so,
   *    delete this exception statement from your version. If you delete this
   *    exception statement from all source files in the program, then also delete
   *    it in the license file.
   */
  
  #pragma once
  
  #include "mongo/db/logical_session_id.h"
  #include "mongo/db/signed_logical_session_id.h"
  #include "mongo/stdx/functional.h"
  #include "mongo/util/periodic_runner.h"
  #include "mongo/util/time_support.h"
  
  namespace mongo {
  
  class ServiceContext;
  
  /**
   * A service-dependent type for the LogicalSessionCache to use to find the
   * current time, schedule periodic refresh jobs, and get a list of sessions
   * that are being used for long-running queries on the service context.
   *
   * Mongod and mongos implement their own classes to fulfill this interface.
   */
  class ServiceLiason {
  public:
      virtual ~ServiceLiason();
  
      /**
       * Return a list of sessions that are currently being used to run operations
       * on this service.
       */
      virtual LogicalSessionIdSet getActiveSessions() const = 0;
  
      /**
       * Schedule a job to be run at regular intervals until the server shuts down.
       *
       * The ServiceLiason should start its background runner on construction, and
       * should continue fielding job requests through scheduleJob until join() is
       * called.
       */
      virtual void scheduleJob(PeriodicRunner::PeriodicJob job) = 0;
  
      /**
       * Stops the service liason from running any more jobs scheduled
       * through scheduleJob. This method may block and wait for background threads to
       * join. Implementations should make it safe for this method to be called
       * multiple times, or concurrently by different threads.
       */
      virtual void join() = 0;
  
      /**
       * Return the current time.
       */
      virtual Date_t now() const = 0;
  
      /**
       * Generates and sets a signature for the fields in this LogicalSessionId.
       *
       * If this method is not able to acquire a key to perform the signature
       * this call will return an error.
       */
      StatusWith<SignedLogicalSessionId> signLsid(OperationContext* opCtx,
                                                  const LogicalSessionId& lsid,
                                                  boost::optional<OID> userId);
  
      /**
       * Validates that this LogicalSessionId was signed with the correct key.
       */
      Status validateLsid(OperationContext* opCtx, const SignedLogicalSessionId& id);
  
  protected:
      /**
       * Returns the service context.
       */
      virtual ServiceContext* _context() = 0;
  };
  
  }  // namespace mongo
  