blob: 35be0ddcbaa1a37e21b6107bc645aa642d436e74 [file] [log] [blame]
// 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 <stout/result.hpp>
#include <process/future.hpp>
namespace zookeeper {
// Forward declaration.
class LeaderDetectorProcess;
// Provides an abstraction for detecting the leader of a ZooKeeper
// group.
class LeaderDetector
// The specified 'group' is expected to outlive the detector.
explicit LeaderDetector(Group* group);
virtual ~LeaderDetector();
// Returns some membership after an election has occurred and a
// leader (membership) is elected, or none if an election occurs and
// no leader is elected (e.g., all memberships are lost).
// A failed future is returned if the detector is unable to detect
// the leading master due to a non-retryable error.
// Note that the detector transparently tries to recover from
// retryable errors until the group session expires, in which case
// the Future returns None.
// The future is never discarded unless it stays pending when the
// detector destructs.
// The 'previous' result (if any) should be passed back if this
// method is called repeatedly so the detector only returns when it
// gets a different result.
// TODO(xujyan): Use a Stream abstraction instead.
process::Future<Option<Group::Membership>> detect(
const Option<Group::Membership>& previous = None());
LeaderDetectorProcess* process;
} // namespace zookeeper {