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// 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
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License
#include <string>
#include <mesos/zookeeper/group.hpp>
#include <process/future.hpp>
#include <stout/nothing.hpp>
#include <stout/option.hpp>
namespace zookeeper {
// Forward declaration.
class LeaderContenderProcess;
// Provides an abstraction for contending to be the leader of a
// ZooKeeper group.
// Note that the contender is NOT reusable, which means its methods
// are supposed to be called once and the client needs to create a
// new instance to contend again.
class LeaderContender
// The specified 'group' is expected to outlive the contender. The
// specified 'data' is associated with the group membership created
// by this contender. 'label' indicates the label for the znode that
// stores the 'data'.
LeaderContender(Group* group,
const std::string& data,
const Option<std::string>& label);
// Note that the contender's membership, if obtained, is scheduled
// to be cancelled during destruction.
// NOTE: The client should call withdraw() to guarantee that the
// membership is cancelled when its returned future is satisfied.
virtual ~LeaderContender();
// Returns a Future<Nothing> once the contender has achieved
// candidacy (by obtaining a membership) and a failure otherwise.
// The inner Future returns Nothing when the contender is out of
// the contest (i.e. its membership is lost) and a failure if it is
// unable to watch the membership.
// It should be called only once, otherwise a failure is returned.
process::Future<process::Future<Nothing>> contend();
// Returns true if successfully withdrawn from the contest (either
// while contending or has already contended and is watching for
// membership loss).
// A false return value implies that there was no valid group
// membership to cancel, which may be a result of a race to cancel
// an expired membership or because there is nothing to withdraw.
// A failed future is returned if the contender is unable to
// withdraw.
process::Future<bool> withdraw();
LeaderContenderProcess* process;
} // namespace zookeeper {