org.apache.hadoop.util.FlushableLogger.java Source code

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Here is the source code for org.apache.hadoop.util.FlushableLogger.java

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/**
 * 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 org.apache.hadoop.util;

import java.util.Enumeration;
import java.util.HashSet;
import java.util.Set;

import org.apache.commons.logging.*;
import org.apache.log4j.LogManager;
import org.apache.log4j.FileAppender;
import org.apache.log4j.Logger;

/**
 * FlushableLogger can be used for logging messages that should be visible in
 * the system logs immediately. It exposes Log interface, however the calls are
 * much more expensive than simply calling a raw Log. This logger should only be
 * used in non-critical paths!
 * 
 * This implementation causes logs to be flushed when log4j.properties sets
 * bufferedIO option to true. If the option is set to false, this implementation
 * does not change any behavior of logging.
 */
public class FlushableLogger implements Log {

    private final static Log LOG = LogFactory.getLog(FlushableLogger.class);

    // log being wrapped
    private final Log log;

    /**
     * Wrap an instance of Log with a log whose messages are always immediately
     * flushed. Warning: Calls to this logger are much more expensive than to the
     * raw logger.
     */
    public static Log getLogger(Log log) {
        return new FlushableLogger(log);
    }

    private FlushableLogger(Log log) {
        if (log == null) {
            String msg = "Log should not be null";
            LOG.error(msg);
            throw new IllegalArgumentException(msg);
        }
        this.log = log;
    }

    /**
     * Set immediateFlush property for all file appenders.
     */
    private synchronized void setFlush(boolean immediateFlush) {
        try {
            Set<FileAppender> flushedFileAppenders = new HashSet<FileAppender>();
            Enumeration<?> currentLoggers = LogManager.getLoggerRepository().getCurrentLoggers();
            while (currentLoggers.hasMoreElements()) {
                Object nextLogger = currentLoggers.nextElement();
                if (nextLogger instanceof Logger) {
                    Logger currentLogger = (Logger) nextLogger;
                    Enumeration<?> allAppenders = currentLogger.getParent().getAllAppenders();
                    while (allAppenders.hasMoreElements()) {
                        Object nextElement = allAppenders.nextElement();
                        if (nextElement instanceof FileAppender) {
                            FileAppender fileAppender = (FileAppender) nextElement;

                            if (!flushedFileAppenders.contains(fileAppender)) {
                                flushedFileAppenders.add(fileAppender);
                                fileAppender.setImmediateFlush(immediateFlush);
                            }
                        }
                    }
                }
            }
        } catch (Throwable e) {
            LOG.error("Failed flushing logs", e);
        }
    }

    // Log interface

    @Override
    public void debug(Object arg0) {
        debug(arg0, null);
    }

    @Override
    public void debug(Object arg0, Throwable arg1) {
        setFlush(true);
        log.debug(arg0, arg1);
        setFlush(false);
    }

    @Override
    public void error(Object arg0) {
        error(arg0, null);
    }

    @Override
    public void error(Object arg0, Throwable arg1) {
        setFlush(true);
        log.error(arg0, arg1);
        setFlush(false);
    }

    @Override
    public void fatal(Object arg0) {
        fatal(arg0, null);
    }

    @Override
    public void fatal(Object arg0, Throwable arg1) {
        setFlush(true);
        log.fatal(arg0, arg1);
        setFlush(false);
    }

    @Override
    public void info(Object arg0) {
        info(arg0, null);
    }

    @Override
    public void info(Object arg0, Throwable arg1) {
        setFlush(true);
        log.info(arg0, arg1);
        setFlush(false);
    }

    @Override
    public boolean isDebugEnabled() {
        return log.isDebugEnabled();
    }

    @Override
    public boolean isErrorEnabled() {
        return log.isErrorEnabled();
    }

    @Override
    public boolean isFatalEnabled() {
        return log.isErrorEnabled();
    }

    @Override
    public boolean isInfoEnabled() {
        return log.isInfoEnabled();
    }

    @Override
    public boolean isTraceEnabled() {
        return log.isTraceEnabled();
    }

    @Override
    public boolean isWarnEnabled() {
        return log.isWarnEnabled();
    }

    @Override
    public void trace(Object arg0) {
        trace(arg0, null);
    }

    @Override
    public void trace(Object arg0, Throwable arg1) {
        setFlush(true);
        log.trace(arg0, arg1);
        setFlush(false);
    }

    @Override
    public void warn(Object arg0) {
        warn(arg0, null);
    }

    @Override
    public void warn(Object arg0, Throwable arg1) {
        setFlush(true);
        log.warn(arg0, arg1);
        setFlush(false);
    }
}