Initial commit

Functional, without SSO

sources/lib/Log4php/LoggerNDC.php

@@ -0,0 +1,203 @@
+<?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: 1350602 $
+ * @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);
+		}
+	}
+}