1 : <?php
2 : /**
3 : * Licensed to the Apache Software Foundation (ASF) under one or more
4 : * contributor license agreements. See the NOTICE file distributed with
5 : * this work for additional information regarding copyright ownership.
6 : * The ASF licenses this file to You under the Apache License, Version 2.0
7 : * (the "License"); you may not use this file except in compliance with
8 : * the License. You may obtain a copy of the License at
9 : *
10 : * http://www.apache.org/licenses/LICENSE-2.0
11 : *
12 : * Unless required by applicable law or agreed to in writing, software
13 : * distributed under the License is distributed on an "AS IS" BASIS,
14 : * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 : * See the License for the specific language governing permissions and
16 : * limitations under the License.
17 : *
18 : * @package log4php
19 : */
20 :
21 : /**
22 : * The NDC class implements <i>nested diagnostic contexts</i>.
23 : *
24 : * NDC was defined by Neil Harrison in the article "Patterns for Logging
25 : * Diagnostic Messages" part of the book <i>"Pattern Languages of
26 : * Program Design 3"</i> edited by Martin et al.
27 : *
28 : * A Nested Diagnostic Context, or NDC in short, is an instrument
29 : * to distinguish interleaved log output from different sources. Log
30 : * output is typically interleaved when a server handles multiple
31 : * clients near-simultaneously.
32 : *
33 : * This class is similar to the {@link LoggerMDC} class except that it is
34 : * based on a stack instead of a map.
35 : *
36 : * Interleaved log output can still be meaningful if each log entry
37 : * from different contexts had a distinctive stamp. This is where NDCs
38 : * come into play.
39 : *
40 : * <b>Note that NDCs are managed on a per thread basis</b>.
41 : *
42 : * NDC operations such as {@link push()}, {@link pop()},
43 : * {@link clear()}, {@link getDepth()} and {@link setMaxDepth()}
44 : * affect the NDC of the <i>current</i> thread only. NDCs of other
45 : * threads remain unaffected.
46 : *
47 : * For example, a servlet can build a per client request NDC
48 : * consisting the clients host name and other information contained in
49 : * the the request. <i>Cookies</i> are another source of distinctive
50 : * information. To build an NDC one uses the {@link push()}
51 : * operation.
52 : *
53 : * Simply put,
54 : *
55 : * - Contexts can be nested.
56 : * - When entering a context, call <kbd>LoggerNDC::push()</kbd>
57 : * As a side effect, if there is no nested diagnostic context for the
58 : * current thread, this method will create it.
59 : * - When leaving a context, call <kbd>LoggerNDC::pop()</kbd>
60 : * - <b>When exiting a thread make sure to call {@link remove()}</b>
61 : *
62 : * There is no penalty for forgetting to match each
63 : * <kbd>push</kbd> operation with a corresponding <kbd>pop</kbd>,
64 : * except the obvious mismatch between the real application context
65 : * and the context set in the NDC.
66 : *
67 : * If configured to do so, {@link LoggerPatternLayout} and {@link LoggerLayoutTTCC}
68 : * instances automatically retrieve the nested diagnostic
69 : * context for the current thread without any user intervention.
70 : * Hence, even if a servlet is serving multiple clients
71 : * simultaneously, the logs emanating from the same code (belonging to
72 : * the same category) can still be distinguished because each client
73 : * request will have a different NDC tag.
74 : *
75 : * Example:
76 : *
77 : * {@example ../../examples/php/ndc.php 19}<br>
78 : *
79 : * With the properties file:
80 : *
81 : * {@example ../../examples/resources/ndc.properties 18}<br>
82 : *
83 : * Will result in the following (notice the conn and client ids):
84 : *
85 : * <pre>
86 : * 2009-09-13 19:04:27 DEBUG root conn=1234: just received a new connection in src/examples/php/ndc.php at 23
87 : * 2009-09-13 19:04:27 DEBUG root conn=1234 client=ab23: some more messages that can in src/examples/php/ndc.php at 25
88 : * 2009-09-13 19:04:27 DEBUG root conn=1234 client=ab23: now related to a client in src/examples/php/ndc.php at 26
89 : * 2009-09-13 19:04:27 DEBUG root : back and waiting for new connections in src/examples/php/ndc.php at 29
90 : * </pre>
91 : *
92 : * @version $Revision: 1166187 $
93 : * @package log4php
94 : * @since 0.3
95 : */
96 : class LoggerNDC {
97 :
98 : /** This is the repository of NDC stack */
99 : private static $stack = array();
100 :
101 : /**
102 : * Clear any nested diagnostic information if any. This method is
103 : * useful in cases where the same thread can be potentially used
104 : * over and over in different unrelated contexts.
105 : *
106 : * <p>This method is equivalent to calling the {@link setMaxDepth()}
107 : * method with a zero <var>maxDepth</var> argument.
108 : */
109 : public static function clear() {
110 3 : self::$stack = array();
111 3 : }
112 :
113 : /**
114 : * Never use this method directly, use the {@link LoggerLoggingEvent::getNDC()} method instead.
115 : * @return array
116 : */
117 : public static function get() {
118 11 : return implode(' ', self::$stack);
119 : }
120 :
121 : /**
122 : * Get the current nesting depth of this diagnostic context.
123 : *
124 : * @see setMaxDepth()
125 : * @return integer
126 : */
127 : public static function getDepth() {
128 2 : return count(self::$stack);
129 : }
130 :
131 : /**
132 : * Clients should call this method before leaving a diagnostic
133 : * context.
134 : *
135 : * <p>The returned value is the value that was pushed last. If no
136 : * context is available, then the empty string "" is returned.</p>
137 : *
138 : * @return string The innermost diagnostic context.
139 : */
140 : public static function pop() {
141 1 : if(count(self::$stack) > 0) {
142 1 : return array_pop(self::$stack);
143 : } else {
144 1 : return '';
145 : }
146 : }
147 :
148 : /**
149 : * Looks at the last diagnostic context at the top of this NDC
150 : * without removing it.
151 : *
152 : * <p>The returned value is the value that was pushed last. If no
153 : * context is available, then the empty string "" is returned.</p>
154 : * @return string The innermost diagnostic context.
155 : */
156 : public static function peek(){
157 1 : if(count(self::$stack) > 0) {
158 1 : return end(self::$stack);
159 : } else {
160 1 : return '';
161 : }
162 : }
163 :
164 : /**
165 : * Push new diagnostic context information for the current thread.
166 : *
167 : * <p>The contents of the <var>message</var> parameter is
168 : * determined solely by the client.
169 : *
170 : * @param string $message The new diagnostic context information.
171 : */
172 : public static function push($message) {
173 3 : array_push(self::$stack, (string)$message);
174 3 : }
175 :
176 : /**
177 : * Remove the diagnostic context for this thread.
178 : */
179 : public static function remove() {
180 1 : LoggerNDC::clear();
181 1 : }
182 :
183 : /**
184 : * Set maximum depth of this diagnostic context. If the current
185 : * depth is smaller or equal to <var>maxDepth</var>, then no
186 : * action is taken.
187 : *
188 : * <p>This method is a convenient alternative to multiple
189 : * {@link pop()} calls. Moreover, it is often the case that at
190 : * the end of complex call sequences, the depth of the NDC is
191 : * unpredictable. The {@link setMaxDepth()} method circumvents
192 : * this problem.
193 : *
194 : * @param integer $maxDepth
195 : * @see getDepth()
196 : */
197 : public static function setMaxDepth($maxDepth) {
198 1 : $maxDepth = (int)$maxDepth;
199 1 : if(LoggerNDC::getDepth() > $maxDepth) {
200 1 : self::$stack = array_slice(self::$stack, 0, $maxDepth);
201 1 : }
202 1 : }
203 : }
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