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 */
018
019package org.apache.hadoop.metrics2.lib;
020
021import org.apache.hadoop.classification.InterfaceAudience;
022import org.apache.hadoop.classification.InterfaceStability;
023import org.apache.hadoop.metrics2.MetricsInfo;
024import org.apache.hadoop.metrics2.MetricsTag;
025import org.slf4j.Logger;
026import org.slf4j.LoggerFactory;
027
028import java.util.LinkedHashMap;
029import java.util.Map;
030
031/**
032 * Helpers to create interned metrics info.
033 */
034@InterfaceAudience.Public
035@InterfaceStability.Evolving
036public class Interns {
037  private static final Logger LOG = LoggerFactory.getLogger(Interns.class);
038
039  // A simple intern cache with two keys
040  // (to avoid creating new (combined) key objects for lookup)
041  private static abstract class CacheWith2Keys<K1, K2, V> {
042    private final Map<K1, Map<K2, V>> k1Map =
043        new LinkedHashMap<K1, Map<K2, V>>() {
044      private static final long serialVersionUID = 1L;
045      private boolean gotOverflow = false;
046      @Override
047      protected boolean removeEldestEntry(Map.Entry<K1, Map<K2, V>> e) {
048        boolean overflow = expireKey1At(size());
049        if (overflow && !gotOverflow) {
050          LOG.info("Metrics intern cache overflow at {} for {}", size(), e);
051          gotOverflow = true;
052        }
053        return overflow;
054      }
055    };
056
057    abstract protected boolean expireKey1At(int size);
058    abstract protected boolean expireKey2At(int size);
059    abstract protected V newValue(K1 k1, K2 k2);
060
061    synchronized V add(K1 k1, K2 k2) {
062      Map<K2, V> k2Map = k1Map.get(k1);
063      if (k2Map == null) {
064        k2Map = new LinkedHashMap<K2, V>() {
065          private static final long serialVersionUID = 1L;
066          private boolean gotOverflow = false;
067          @Override protected boolean removeEldestEntry(Map.Entry<K2, V> e) {
068            boolean overflow = expireKey2At(size());
069            if (overflow && !gotOverflow) {
070              LOG.info("Metrics intern cache overflow at {} for {}", size(), e);
071              gotOverflow = true;
072            }
073            return overflow;
074          }
075        };
076        k1Map.put(k1, k2Map);
077      }
078      V v = k2Map.get(k2);
079      if (v == null) {
080        v = newValue(k1, k2);
081        k2Map.put(k2, v);
082      }
083      return v;
084    }
085  }
086
087  // Sanity limits in case of misuse/abuse.
088  static final int MAX_INFO_NAMES = 2010;
089  static final int MAX_INFO_DESCS = 100;  // distinct per name
090
091  enum Info {
092    INSTANCE;
093
094    final CacheWith2Keys<String, String, MetricsInfo> cache =
095        new CacheWith2Keys<String, String, MetricsInfo>() {
096
097      @Override protected boolean expireKey1At(int size) {
098        return size > MAX_INFO_NAMES;
099      }
100
101      @Override protected boolean expireKey2At(int size) {
102        return size > MAX_INFO_DESCS;
103      }
104
105      @Override protected MetricsInfo newValue(String name, String desc) {
106        return new MetricsInfoImpl(name, desc);
107      }
108    };
109  }
110
111  /**
112   * Get a metric info object.
113   * @param name Name of metric info object
114   * @param description Description of metric info object
115   * @return an interned metric info object
116   */
117  public static MetricsInfo info(String name, String description) {
118    return Info.INSTANCE.cache.add(name, description);
119  }
120
121  // Sanity limits
122  static final int MAX_TAG_NAMES = 100;
123  static final int MAX_TAG_VALUES = 1000; // distinct per name
124
125  enum Tags {
126    INSTANCE;
127
128    final CacheWith2Keys<MetricsInfo, String, MetricsTag> cache =
129        new CacheWith2Keys<MetricsInfo, String, MetricsTag>() {
130
131      @Override protected boolean expireKey1At(int size) {
132        return size > MAX_TAG_NAMES;
133      }
134
135      @Override protected boolean expireKey2At(int size) {
136        return size > MAX_TAG_VALUES;
137      }
138
139      @Override protected MetricsTag newValue(MetricsInfo info, String value) {
140        return new MetricsTag(info, value);
141      }
142    };
143  }
144
145  /**
146   * Get a metrics tag.
147   * @param info  of the tag
148   * @param value of the tag
149   * @return an interned metrics tag
150   */
151  public static MetricsTag tag(MetricsInfo info, String value) {
152    return Tags.INSTANCE.cache.add(info, value);
153  }
154
155  /**
156   * Get a metrics tag.
157   * @param name  of the tag
158   * @param description of the tag
159   * @param value of the tag
160   * @return an interned metrics tag
161   */
162  public static MetricsTag tag(String name, String description, String value) {
163    return Tags.INSTANCE.cache.add(info(name, description), value);
164  }
165}