ppkarwasz commented on code in PR #2249:
URL: https://github.com/apache/logging-log4j2/pull/2249#discussion_r1467457061
##########
log4j-api/src/main/java/org/apache/logging/log4j/status/StatusLogger.java:
##########
@@ -16,311 +16,567 @@
*/
package org.apache.logging.log4j.status;
-import java.io.Closeable;
+import static java.util.Objects.requireNonNull;
+
+import edu.umd.cs.findbugs.annotations.Nullable;
import java.io.IOException;
+import java.io.InputStream;
+import java.io.PrintStream;
+import java.net.URL;
+import java.time.format.DateTimeFormatter;
import java.util.ArrayList;
import java.util.Collection;
+import java.util.Collections;
+import java.util.Iterator;
import java.util.List;
+import java.util.Properties;
import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;
-import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
-import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import org.apache.logging.log4j.Level;
import org.apache.logging.log4j.Marker;
import org.apache.logging.log4j.message.Message;
import org.apache.logging.log4j.message.MessageFactory;
import org.apache.logging.log4j.message.ParameterizedNoReferenceMessageFactory;
-import org.apache.logging.log4j.simple.SimpleLogger;
-import org.apache.logging.log4j.simple.SimpleLoggerContext;
import org.apache.logging.log4j.spi.AbstractLogger;
import org.apache.logging.log4j.util.Constants;
-import org.apache.logging.log4j.util.PropertiesUtil;
/**
- * Records events that occur in the logging system. By default, only error
messages are logged to {@link System#err}.
- * Normally, the Log4j StatusLogger is configured via the root {@code
<Configuration status="LEVEL"/>} node in a Log4j
- * configuration file. However, this can be overridden via a system property
named
- * {@value #DEFAULT_STATUS_LISTENER_LEVEL} and will work with any Log4j
provider.
- *
- * @see SimpleLogger
- * @see SimpleLoggerContext
+ * Records events that occur in the logging system.
+ * {@link StatusLogger} is expected to be a standalone, self-sufficient
component that the logging system can rely on for low-level logging purposes.
+ * <h3>Listeners</h3>
+ * <p>
+ * Each recorded event will first get buffered and used to notify the
registered {@link StatusListener}s.
+ * Listener registry is always initialized with a <em>default listener</em>,
which is a {@link StatusConsoleListener}.
+ * </p>
+ * <p>
+ * You can programmatically register listeners using {@link
#registerListener(StatusListener)} method.
+ * </p>
+ * <h3>Configuration</h3>
+ * <p>
+ * The {@code StatusLogger} can be configured in following ways:
+ * </p>
+ * <ol>
+ * <li>Passing system properties to the Java process (e.g., {@code
-Dlog4j2.StatusLogger.level=INFO})</li>
+ * <li>Providing properties in a {@value StatusLogger#PROPERTIES_FILE_NAME}
file in the classpath</li>
+ * <li>Using Log4j configuration (i.e., {@code <Configuration status="WARN"
dest="out">} in a {@code log4j2.xml} in the classpath)</li>
+ * </ol>
+ * <p>
+ * It is crucial to understand that there is a time between the first {@code
StatusLogger} access and a configuration file (e.g., {@code log4j2.xml}) read.
+ * Consider the following example:
+ * </p>
+ * <ol>
+ * <li>The default level is {@code ERROR}</li>
+ * <li>You have <Configuration status="WARN">} in your {@code log4j2.xml}</li>
+ * <li>Until your {@code log4j2.xml} configuration is read, the effective
level will be {@code ERROR}</li>
+ * <li>Once your {@code log4j2.xml} configuration is read, the effective level
will be {@code WARN} as you configured</li>
+ * </ol>
+ * <p>
+ * Hence, unless you use either system properties or {@value
StatusLogger#PROPERTIES_FILE_NAME} file in the classpath, there is a time
window that only the defaults will be effective.
+ * </p>
+ * <p>
+ * {@code StatusLogger} is designed as a singleton class accessed statically.
+ * If you are running an application containing multiple Log4j configurations
(e.g., in a servlet environment with multiple containers) and you happen to
have differing {@code StatusLogger} configurations (e.g, one {@code log4j2.xml}
containing {@code <Configuration status="ERROR">} while the other {@code
<Configuration status="INFO">}), the last loaded configuration will be
effective one.
+ * </p>
+ * <h3>Debug mode</h3>
+ * <p>
+ * When the {@value Constants#LOG4J2_DEBUG} system property is present, any
level-related filtering will be skipped and all events will be notified to
listeners.
+ * </p>
*/
-public final class StatusLogger extends AbstractLogger {
+public class StatusLogger extends AbstractLogger {
+
+ private static final long serialVersionUID = 2L;
+
+ /**
+ * The name of the system property that enables debug mode in its presence.
+ * <p>
+ * This is a local clone of {@link Constants#LOG4J2_DEBUG}.
+ * The cloning is necessary to avoid cyclic initialization.
+ * </p>
+ */
+ public static final String DEBUG_PROPERTY_NAME = "log4j2.debug";
+
+ /**
+ * The name of the system property that can be configured with the maximum
number of events buffered.
+ * <p>
+ * Once the limit is reached, older entries will be removed as new entries
are added.
+ * </p>
+ *
+ * @since 2.23.0
+ */
+ public static final String BUFFER_CAPACITY_PROPERTY_NAME =
"log4j2.status.entries";
+
+ /**
+ * The default value of the {@link #BUFFER_CAPACITY_PROPERTY_NAME} system
property: {@code 0}.
+ *
+ * @since 2.23.0
+ */
+ public static final int BUFFER_CAPACITY_DEFAULT_VALUE = 0;
/**
- * System property that can be configured with the number of entries in
the queue. Once the limit is reached older
- * entries will be removed as new entries are added.
+ * The name of the system property that can be configured with the maximum
number of events buffered.
+ * <p>
+ * Once the limit is reached, older entries will be removed as new entries
are added.
+ * </p>
+ *
+ * @deprecated Use {@link #BUFFER_CAPACITY_PROPERTY_NAME} instead.
+ */
+ @Deprecated
+ public static final String MAX_STATUS_ENTRIES =
BUFFER_CAPACITY_PROPERTY_NAME;
Review Comment:
That is fine with me.
Do we need for the new constants to be `public`?
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