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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/mesos.hpp>
#include <process/future.hpp>
#include <stout/duration.hpp>
#include <stout/option.hpp>
#include <stout/try.hpp>
namespace mesos {
namespace master {
namespace detector {
* An abstraction of a Master detector which can be used to
* detect the leading master from a group.
class MasterDetector
* Creates a master detector. If `masterDetectorModule` contains a valid
* module name (that is, a name that matches the name specified in a JSON
* file/string passed into the command-line invocation using the `--modules`
* flag), the result is the `MasterDetector` returned by the module.
* Additional parameters required to create an object of the detector type are
* expected to be specified in the JSON's `parameter` object. In command-line
* invocations, the value of `masterDetectorModule` is expected to come from
* the `--master_detector` flag.
* If `masterDetectorModule` is `None`, `zk` is checked and if it contains a
* valid `zk://` or `file://` path (passed in using the `--master` flag), an
* instance of ZooKeeperMasterDetector is returned.
* If both arguments are `None`, `StandaloneMasterDetector` is returned.
static Try<MasterDetector*> create(
const Option<std::string>& zk,
const Option<std::string>& masterDetectorModule = None(),
const Option<Duration>& zkSessionTimeout = None());
virtual ~MasterDetector() = 0;
* Returns MasterInfo after an election has occurred and the elected
* master is different than that specified (if any), or NONE if an
* election occurs and no master is elected (e.g., all masters 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.
* 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.
virtual process::Future<Option<MasterInfo>> detect(
const Option<MasterInfo>& previous = None()) = 0;
} // namespace detector {
} // namespace master {
} // namespace mesos {