| <?php |
| /** |
| * 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 log4php |
| */ |
| |
| /** |
| * The NDC class implements <i>nested diagnostic contexts</i>. |
| * |
| * NDC was defined by Neil Harrison in the article "Patterns for Logging |
| * Diagnostic Messages" part of the book <i>"Pattern Languages of |
| * Program Design 3"</i> edited by Martin et al. |
| * |
| * A Nested Diagnostic Context, or NDC in short, is an instrument |
| * to distinguish interleaved log output from different sources. Log |
| * output is typically interleaved when a server handles multiple |
| * clients near-simultaneously. |
| * |
| * This class is similar to the {@link LoggerMDC} class except that it is |
| * based on a stack instead of a map. |
| * |
| * Interleaved log output can still be meaningful if each log entry |
| * from different contexts had a distinctive stamp. This is where NDCs |
| * come into play. |
| * |
| * <b>Note that NDCs are managed on a per thread basis</b>. |
| * |
| * NDC operations such as {@link push()}, {@link pop()}, |
| * {@link clear()}, {@link getDepth()} and {@link setMaxDepth()} |
| * affect the NDC of the <i>current</i> thread only. NDCs of other |
| * threads remain unaffected. |
| * |
| * For example, a servlet can build a per client request NDC |
| * consisting the clients host name and other information contained in |
| * the the request. <i>Cookies</i> are another source of distinctive |
| * information. To build an NDC one uses the {@link push()} |
| * operation. |
| * |
| * Simply put, |
| * |
| * - Contexts can be nested. |
| * - When entering a context, call <kbd>LoggerNDC::push()</kbd> |
| * As a side effect, if there is no nested diagnostic context for the |
| * current thread, this method will create it. |
| * - When leaving a context, call <kbd>LoggerNDC::pop()</kbd> |
| * - <b>When exiting a thread make sure to call {@link remove()}</b> |
| * |
| * There is no penalty for forgetting to match each |
| * <kbd>push</kbd> operation with a corresponding <kbd>pop</kbd>, |
| * except the obvious mismatch between the real application context |
| * and the context set in the NDC. |
| * |
| * If configured to do so, {@link LoggerPatternLayout} and {@link LoggerLayoutTTCC} |
| * instances automatically retrieve the nested diagnostic |
| * context for the current thread without any user intervention. |
| * Hence, even if a servlet is serving multiple clients |
| * simultaneously, the logs emanating from the same code (belonging to |
| * the same category) can still be distinguished because each client |
| * request will have a different NDC tag. |
| * |
| * Example: |
| * |
| * {@example ../../examples/php/ndc.php 19}<br> |
| * |
| * With the properties file: |
| * |
| * {@example ../../examples/resources/ndc.properties 18}<br> |
| * |
| * Will result in the following (notice the conn and client ids): |
| * |
| * <pre> |
| * 2009-09-13 19:04:27 DEBUG root conn=1234: just received a new connection in src/examples/php/ndc.php at 23 |
| * 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 |
| * 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 |
| * 2009-09-13 19:04:27 DEBUG root : back and waiting for new connections in src/examples/php/ndc.php at 29 |
| * </pre> |
| * |
| * @version $Revision$ |
| * @package log4php |
| * @since 0.3 |
| */ |
| class LoggerNDC { |
| |
| /** This is the repository of NDC stack */ |
| private static $stack = array(); |
| |
| /** |
| * Clear any nested diagnostic information if any. This method is |
| * useful in cases where the same thread can be potentially used |
| * over and over in different unrelated contexts. |
| * |
| * <p>This method is equivalent to calling the {@link setMaxDepth()} |
| * method with a zero <var>maxDepth</var> argument. |
| */ |
| public static function clear() { |
| self::$stack = array(); |
| } |
| |
| /** |
| * Never use this method directly, use the {@link LoggerLoggingEvent::getNDC()} method instead. |
| * @return array |
| */ |
| public static function get() { |
| return implode(' ', self::$stack); |
| } |
| |
| /** |
| * Get the current nesting depth of this diagnostic context. |
| * |
| * @see setMaxDepth() |
| * @return integer |
| */ |
| public static function getDepth() { |
| return count(self::$stack); |
| } |
| |
| /** |
| * Clients should call this method before leaving a diagnostic |
| * context. |
| * |
| * <p>The returned value is the value that was pushed last. If no |
| * context is available, then the empty string "" is returned.</p> |
| * |
| * @return string The innermost diagnostic context. |
| */ |
| public static function pop() { |
| if(count(self::$stack) > 0) { |
| return array_pop(self::$stack); |
| } else { |
| return ''; |
| } |
| } |
| |
| /** |
| * Looks at the last diagnostic context at the top of this NDC |
| * without removing it. |
| * |
| * <p>The returned value is the value that was pushed last. If no |
| * context is available, then the empty string "" is returned.</p> |
| * @return string The innermost diagnostic context. |
| */ |
| public static function peek() { |
| if(count(self::$stack) > 0) { |
| return end(self::$stack); |
| } else { |
| return ''; |
| } |
| } |
| |
| /** |
| * Push new diagnostic context information for the current thread. |
| * |
| * <p>The contents of the <var>message</var> parameter is |
| * determined solely by the client. |
| * |
| * @param string $message The new diagnostic context information. |
| */ |
| public static function push($message) { |
| array_push(self::$stack, (string)$message); |
| } |
| |
| /** |
| * Remove the diagnostic context for this thread. |
| */ |
| public static function remove() { |
| LoggerNDC::clear(); |
| } |
| |
| /** |
| * Set maximum depth of this diagnostic context. If the current |
| * depth is smaller or equal to <var>maxDepth</var>, then no |
| * action is taken. |
| * |
| * <p>This method is a convenient alternative to multiple |
| * {@link pop()} calls. Moreover, it is often the case that at |
| * the end of complex call sequences, the depth of the NDC is |
| * unpredictable. The {@link setMaxDepth()} method circumvents |
| * this problem. |
| * |
| * @param integer $maxDepth |
| * @see getDepth() |
| */ |
| public static function setMaxDepth($maxDepth) { |
| $maxDepth = (int)$maxDepth; |
| if(LoggerNDC::getDepth() > $maxDepth) { |
| self::$stack = array_slice(self::$stack, 0, $maxDepth); |
| } |
| } |
| } |