com.netflix.fenzo.StateMonitor Maven / Gradle / Ivy
/*
* Copyright 2015 Netflix, Inc.
*
* Licensed 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.
*/
package com.netflix.fenzo;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* A monitor to ensure scheduler state is not compromised by concurrent calls that are disallowed.
*/
class StateMonitor {
private final AtomicBoolean lock;
StateMonitor() {
lock = new AtomicBoolean(false);
}
AutoCloseable enter() {
if(!lock.compareAndSet(false, true))
throw new IllegalStateException();
return new AutoCloseable() {
@Override
public void close() throws Exception {
if(!lock.compareAndSet(true, false))
throw new IllegalStateException();
}
};
}
}