| /** |
| * 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 |
| * |
| * 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 org.apache.mesos.state; |
| |
| import java.util.Iterator; |
| import java.util.UUID; |
| |
| import java.util.concurrent.Callable; |
| import java.util.concurrent.ConcurrentHashMap; |
| import java.util.concurrent.ConcurrentMap; |
| import java.util.concurrent.Future; |
| import java.util.concurrent.FutureTask; |
| |
| /** |
| * An in-memory implementation of state. |
| */ |
| public class InMemoryState implements State { |
| @Override |
| public Future<Variable> fetch(String name) { |
| Entry entry = entries.get(name); // Is null if doesn't exist. |
| |
| if (entry == null) { |
| entry = new Entry(); |
| entry.name = name; |
| entry.uuid = UUID.randomUUID(); |
| entry.value = new byte[0]; |
| |
| // We use 'putIfAbsent' because multiple threads might be |
| // attempting to fetch a "new" variable at the same time. |
| if (entries.putIfAbsent(name, entry) != null) { |
| return fetch(name); |
| } |
| } |
| |
| assert entry != null; |
| |
| return futureFrom((Variable) new InMemoryVariable(entry)); |
| } |
| |
| @Override |
| public Future<Variable> store(Variable v) { |
| InMemoryVariable variable = (InMemoryVariable) v; |
| |
| Entry entry = new Entry(); |
| entry.name = variable.entry.name; |
| entry.uuid = UUID.randomUUID(); |
| entry.value = variable.value; |
| |
| if (entries.replace(entry.name, variable.entry, entry)) { |
| return futureFrom((Variable) new InMemoryVariable(entry)); |
| } |
| |
| return futureFrom((Variable) null); |
| } |
| |
| @Override |
| public Future<Boolean> expunge(Variable v) { |
| InMemoryVariable variable = (InMemoryVariable) v; |
| |
| return futureFrom(entries.remove(variable.entry.name, variable.entry)); |
| } |
| |
| @Override |
| public Future<Iterator<String>> names() { |
| return futureFrom(entries.keySet().iterator()); |
| } |
| |
| private static class InMemoryVariable extends Variable { |
| private InMemoryVariable(Entry entry) { |
| this(entry, null); |
| } |
| |
| private InMemoryVariable(Entry entry, byte[] value) { |
| this.entry = entry; |
| this.value = value; |
| } |
| |
| @Override |
| public byte[] value() { |
| if (this.value != null) { |
| return this.value; |
| } else { |
| return this.entry.value; |
| } |
| } |
| |
| @Override |
| public Variable mutate(byte[] value) { |
| return new InMemoryVariable(entry, value); |
| } |
| |
| final Entry entry; |
| final byte[] value; |
| } |
| |
| private static class Entry { |
| @Override |
| public boolean equals(Object that) { |
| if (that instanceof Entry) { |
| return uuid.equals(((Entry) that).uuid); |
| } |
| |
| return false; |
| } |
| |
| @Override |
| public int hashCode() { |
| return uuid.hashCode(); |
| } |
| |
| String name; |
| UUID uuid; |
| byte[] value; |
| } |
| |
| private static <T> Future<T> futureFrom(final T t) { |
| FutureTask<T> future = new FutureTask<T>(new Callable<T>() { |
| public T call() { |
| return t; |
| }}); |
| future.run(); |
| return future; |
| } |
| |
| private final ConcurrentMap<String, Entry> entries = |
| new ConcurrentHashMap<String, Entry>(); |
| } |