org.apache.hadoop.metrics2.lib.Interns.java Source code

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Here is the source code for org.apache.hadoop.metrics2.lib.Interns.java

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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
 *
 *     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.hadoop.metrics2.lib;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.metrics2.MetricsInfo;
import org.apache.hadoop.metrics2.MetricsTag;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.LinkedHashMap;
import java.util.Map;

/**
 * Helpers to create interned metrics info.
 */
@InterfaceAudience.Public
@InterfaceStability.Evolving
public class Interns {
    private static final Logger LOG = LoggerFactory.getLogger(Interns.class);

    // A simple intern cache with two keys
    // (to avoid creating new (combined) key objects for lookup)
    private static abstract class CacheWith2Keys<K1, K2, V> {
        private final Map<K1, Map<K2, V>> k1Map = new LinkedHashMap<K1, Map<K2, V>>() {
            private static final long serialVersionUID = 1L;
            private boolean gotOverflow = false;

            @Override
            protected boolean removeEldestEntry(Map.Entry<K1, Map<K2, V>> e) {
                boolean overflow = expireKey1At(size());
                if (overflow && !gotOverflow) {
                    LOG.info("Metrics intern cache overflow at {} for {}", size(), e);
                    gotOverflow = true;
                }
                return overflow;
            }
        };

        abstract protected boolean expireKey1At(int size);

        abstract protected boolean expireKey2At(int size);

        abstract protected V newValue(K1 k1, K2 k2);

        synchronized V add(K1 k1, K2 k2) {
            Map<K2, V> k2Map = k1Map.get(k1);
            if (k2Map == null) {
                k2Map = new LinkedHashMap<K2, V>() {
                    private static final long serialVersionUID = 1L;
                    private boolean gotOverflow = false;

                    @Override
                    protected boolean removeEldestEntry(Map.Entry<K2, V> e) {
                        boolean overflow = expireKey2At(size());
                        if (overflow && !gotOverflow) {
                            LOG.info("Metrics intern cache overflow at {} for {}", size(), e);
                            gotOverflow = true;
                        }
                        return overflow;
                    }
                };
                k1Map.put(k1, k2Map);
            }
            V v = k2Map.get(k2);
            if (v == null) {
                v = newValue(k1, k2);
                k2Map.put(k2, v);
            }
            return v;
        }
    }

    // Sanity limits in case of misuse/abuse.
    static final int MAX_INFO_NAMES = 2010;
    static final int MAX_INFO_DESCS = 100; // distinct per name

    enum Info {
        INSTANCE;

        final CacheWith2Keys<String, String, MetricsInfo> cache = new CacheWith2Keys<String, String, MetricsInfo>() {

            @Override
            protected boolean expireKey1At(int size) {
                return size > MAX_INFO_NAMES;
            }

            @Override
            protected boolean expireKey2At(int size) {
                return size > MAX_INFO_DESCS;
            }

            @Override
            protected MetricsInfo newValue(String name, String desc) {
                return new MetricsInfoImpl(name, desc);
            }
        };
    }

    /**
     * Get a metric info object.
     * @param name Name of metric info object
     * @param description Description of metric info object
     * @return an interned metric info object
     */
    public static MetricsInfo info(String name, String description) {
        return Info.INSTANCE.cache.add(name, description);
    }

    // Sanity limits
    static final int MAX_TAG_NAMES = 100;
    static final int MAX_TAG_VALUES = 1000; // distinct per name

    enum Tags {
        INSTANCE;

        final CacheWith2Keys<MetricsInfo, String, MetricsTag> cache = new CacheWith2Keys<MetricsInfo, String, MetricsTag>() {

            @Override
            protected boolean expireKey1At(int size) {
                return size > MAX_TAG_NAMES;
            }

            @Override
            protected boolean expireKey2At(int size) {
                return size > MAX_TAG_VALUES;
            }

            @Override
            protected MetricsTag newValue(MetricsInfo info, String value) {
                return new MetricsTag(info, value);
            }
        };
    }

    /**
     * Get a metrics tag.
     * @param info  of the tag
     * @param value of the tag
     * @return an interned metrics tag
     */
    public static MetricsTag tag(MetricsInfo info, String value) {
        return Tags.INSTANCE.cache.add(info, value);
    }

    /**
     * Get a metrics tag.
     * @param name  of the tag
     * @param description of the tag
     * @param value of the tag
     * @return an interned metrics tag
     */
    public static MetricsTag tag(String name, String description, String value) {
        return Tags.INSTANCE.cache.add(info(name, description), value);
    }
}