001/** 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, software 013 * distributed under the License is distributed on an "AS IS" BASIS, 014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 015 * See the License for the specific language governing permissions and 016 * limitations under the License. 017 */ 018package org.apache.hadoop.fs; 019 020import java.util.Iterator; 021import java.util.Map.Entry; 022import java.util.NavigableMap; 023import java.util.NoSuchElementException; 024import java.util.TreeMap; 025 026import org.apache.hadoop.classification.InterfaceAudience; 027 028/** 029 * Stores global storage statistics objects. 030 */ 031@InterfaceAudience.Public 032public enum GlobalStorageStatistics { 033 /** 034 * The GlobalStorageStatistics singleton. 035 */ 036 INSTANCE; 037 038 /** 039 * A map of all global StorageStatistics objects, indexed by name. 040 */ 041 private final NavigableMap<String, StorageStatistics> map = new TreeMap<>(); 042 043 /** 044 * A callback API for creating new StorageStatistics instances. 045 */ 046 public interface StorageStatisticsProvider { 047 StorageStatistics provide(); 048 } 049 050 /** 051 * Get the StorageStatistics object with the given name. 052 * 053 * @param name The storage statistics object name. 054 * @return The StorageStatistics object with the given name, or 055 * null if there is none. 056 */ 057 public synchronized StorageStatistics get(String name) { 058 return map.get(name); 059 } 060 061 /** 062 * Create or return the StorageStatistics object with the given name. 063 * 064 * @param name The storage statistics object name. 065 * @param provider An object which can create a new StorageStatistics 066 * object if needed. 067 * @return The StorageStatistics object with the given name. 068 * @throws RuntimeException If the StorageStatisticsProvider provides a null 069 * object or a new StorageStatistics object with the 070 * wrong name. 071 */ 072 public synchronized StorageStatistics put(String name, 073 StorageStatisticsProvider provider) { 074 StorageStatistics stats = map.get(name); 075 if (stats != null) { 076 return stats; 077 } 078 stats = provider.provide(); 079 if (stats == null) { 080 throw new RuntimeException("StorageStatisticsProvider for " + name + 081 " should not provide a null StorageStatistics object."); 082 } 083 if (!stats.getName().equals(name)) { 084 throw new RuntimeException("StorageStatisticsProvider for " + name + 085 " provided a StorageStatistics object for " + stats.getName() + 086 " instead."); 087 } 088 map.put(name, stats); 089 return stats; 090 } 091 092 /** 093 * Reset all global storage statistics. 094 */ 095 public synchronized void reset() { 096 for (StorageStatistics statistics : map.values()) { 097 statistics.reset(); 098 } 099 } 100 101 /** 102 * Get an iterator that we can use to iterate throw all the global storage 103 * statistics objects. 104 */ 105 synchronized public Iterator<StorageStatistics> iterator() { 106 Entry<String, StorageStatistics> first = map.firstEntry(); 107 return new StorageIterator((first == null) ? null : first.getValue()); 108 } 109 110 private class StorageIterator implements Iterator<StorageStatistics> { 111 private StorageStatistics next = null; 112 113 StorageIterator(StorageStatistics first) { 114 this.next = first; 115 } 116 117 @Override 118 public boolean hasNext() { 119 return (next != null); 120 } 121 122 @Override 123 public StorageStatistics next() { 124 if (next == null) { 125 throw new NoSuchElementException(); 126 } 127 synchronized (GlobalStorageStatistics.this) { 128 StorageStatistics cur = next; 129 Entry<String, StorageStatistics> nextEntry = 130 map.higherEntry(cur.getName()); 131 next = (nextEntry == null) ? null : nextEntry.getValue(); 132 return cur; 133 } 134 } 135 136 @Override 137 public void remove() { 138 throw new UnsupportedOperationException(); 139 } 140 } 141}