001/**
002 * Logback: the reliable, generic, fast and flexible logging framework.
003 * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
004 *
005 * This program and the accompanying materials are dual-licensed under
006 * either the terms of the Eclipse Public License v1.0 as published by
007 * the Eclipse Foundation
008 *
009 *   or (per the licensee's choosing)
010 *
011 * under the terms of the GNU Lesser General Public License version 2.1
012 * as published by the Free Software Foundation.
013 */
014package ch.qos.logback.classic.util;
015
016import java.util.Collections;
017import java.util.Deque;
018import java.util.HashMap;
019import java.util.Map;
020import java.util.Set;
021
022import org.slf4j.helpers.ThreadLocalMapOfStacks;
023import org.slf4j.spi.MDCAdapter;
024
025/**
026 * A <em>Mapped Diagnostic Context</em>, or MDC in short, is an instrument for
027 * distinguishing interleaved log output from different sources. Log output is
028 * typically interleaved when a server handles multiple clients
029 * near-simultaneously.
030 * <p/>
031 * <b><em>The MDC is managed on a per thread basis</em></b>. Note that a child
032 * thread <b>does not</b> inherit the mapped diagnostic context of its parent.
033 * <p/>
034 * <p/>
035 * For more information about MDC, please refer to the online manual at
036 * http://logback.qos.ch/manual/mdc.html
037 *
038 * @author Ceki G&uuml;lc&uuml;
039 */
040public class LogbackMDCAdapterSimple implements MDCAdapter {
041
042
043    // We wish to avoid unnecessarily copying of the map. To ensure
044    // efficient/timely copying, we have a variable keeping track of the previous
045    // operation. A copy is necessary on 'put' or 'remove' but only if the last
046    // operation was a 'get'. Get operations never necessitate a copy nor
047    // successive 'put/remove' operations, only a get followed by a 'put/remove'
048    // requires copying the map.
049    // See http://jira.qos.ch/browse/LOGBACK-620 for the original discussion.
050
051    // We no longer use CopyOnInheritThreadLocal in order to solve LBCLASSIC-183
052    // Initially the contents of the thread local in parent and child threads
053    // reference the same map. However, as soon as a thread invokes the put()
054    // method, the maps diverge as they should.
055//    final ThreadLocal<Map<String, String>> modifiableMap = new ThreadLocal<Map<String, String>>();
056
057    final ThreadLocal<Map<String, String>> threadLocalUnmodifiableMap = new ThreadLocal<Map<String, String>>();
058
059//    private static final int WRITE_OPERATION = 1;
060//    private static final int MAP_COPY_OPERATION = 2;
061
062    // keeps track of the previous operation performed
063//    final ThreadLocal<Integer> previousOperation = new ThreadLocal<Integer>();
064
065    private final ThreadLocalMapOfStacks threadLocalMapOfDeques = new ThreadLocalMapOfStacks();
066    
067//    private Integer getAndSetPreviousOperation(int op) {
068//        Integer penultimateOp = previousOperation.get();
069//        previousOperation.set(op);
070//        return penultimateOp;
071//    }
072
073//    private boolean wasPreviousOpReadOrNull(Integer lastOp) {
074//        return lastOp == null || lastOp.intValue() == MAP_COPY_OPERATION;
075//    }
076
077//    private Map<String, String> duplicateAndInsertNewMap(Map<String, String> oldMap) {
078//        Map<String, String> newMap = duplicateOldMap(oldMap);
079//        modifiableMap.set(newMap);
080//        return newMap;
081//    }
082
083    private Map<String, String> duplicateMap(Map<String, String> oldMap) {
084        if(oldMap != null)
085            return new HashMap<>(oldMap);
086        else
087            return new HashMap<>();
088    }
089
090    /**
091     * Put a context value (the <code>val</code> parameter) as identified with the
092     * <code>key</code> parameter into the current thread's context map. Note that
093     * contrary to log4j, the <code>val</code> parameter can be null.
094     * <p/>
095     * <p/>
096     * If the current thread does not have a context map it is created as a side
097     * effect of this call.
098     *
099     * @throws IllegalArgumentException in case the "key" parameter is null
100     */
101    public void put(String key, String val) throws IllegalArgumentException {
102        if (key == null) {
103            throw new IllegalArgumentException("key cannot be null");
104        }
105
106        Map<String, String> oldMap = threadLocalUnmodifiableMap.get();
107        Map<String, String> newMap = duplicateMap(oldMap);
108        newMap.put(key, val);
109        makeUnmodifiableAndThreadLocalSet(newMap);
110    }
111
112    private void makeUnmodifiableAndThreadLocalSet(Map<String, String> aMap) {
113        Map<String, String> unmodifiable = Collections.unmodifiableMap(aMap);
114        threadLocalUnmodifiableMap.set(unmodifiable);
115    }
116
117    /**
118     * Remove the context identified by the <code>key</code> parameter.
119     * <p/>
120     */
121    public void remove(String key) {
122        if (key == null) {
123            return;
124        }
125        Map<String, String> oldMap = threadLocalUnmodifiableMap.get();
126        if (oldMap == null)
127            return;
128
129        Map<String, String> newMap = duplicateMap(oldMap);
130        newMap.remove(key);
131        makeUnmodifiableAndThreadLocalSet(newMap);
132    }
133
134    /**
135     * Clear all entries in the MDC.
136     */
137    public void clear() {
138        threadLocalUnmodifiableMap.remove();
139    }
140
141    /**
142     * Get the context identified by the <code>key</code> parameter.
143     * <p/>
144     */
145    public String get(String key) {
146        final Map<String, String> map = threadLocalUnmodifiableMap.get();
147        if ((map != null) && (key != null)) {
148            return map.get(key);
149        } else {
150            return null;
151        }
152    }
153
154    /**
155     * Get the current thread's MDC as a map. This method is intended to be used
156     * internally.
157     */
158    public Map<String, String> getPropertyMap() {
159        return threadLocalUnmodifiableMap.get();
160    }
161
162    /**
163     * Returns the keys in the MDC as a {@link Set}. The returned value can be null.
164     */
165    public Set<String> getKeys() {
166        Map<String, String> map = getPropertyMap();
167
168        if (map != null) {
169            return map.keySet();
170        } else {
171            return null;
172        }
173    }
174
175    /**
176     * Return a copy of the current thread's context map. Returned value may be
177     * null.
178     */
179    public Map<String, String> getCopyOfContextMap() {
180        Map<String, String> hashMap = threadLocalUnmodifiableMap.get();
181        return duplicateMap(hashMap);
182    }
183
184    /**
185     * Set the MDC map to the map passed as parameter.
186     *
187     * @param contextMap the new map
188     */
189    public void setContextMap(Map<String, String> contextMap) {
190        duplicateMap(contextMap);
191    }
192    
193    @Override
194    public void pushByKey(String key, String value) {
195        threadLocalMapOfDeques.pushByKey(key, value);
196    }
197
198    @Override
199    public String popByKey(String key) {
200        return threadLocalMapOfDeques.popByKey(key);    
201     }
202
203    @Override
204    public Deque<String> getCopyOfDequeByKey(String key) {
205        return threadLocalMapOfDeques.getCopyOfDequeByKey(key);
206    }
207    @Override
208    public void clearDequeByKey(String key) {
209        threadLocalMapOfDeques.clearDequeByKey(key);
210    }
211}