com.twitter.common.net.http.handlers.LogConfig.java Source code

Introduction

Here is the source code for com.twitter.common.net.http.handlers.LogConfig.java

Source

// =================================================================================================
// Copyright 2011 Twitter, Inc.
// -------------------------------------------------------------------------------------------------
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this work except in compliance with the License.
// You may obtain a copy of the License in the LICENSE file, or 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 com.twitter.common.net.http.handlers;

import java.io.IOException;
import java.util.List;
import java.util.logging.Handler;
import java.util.logging.Level;
import java.util.logging.LogManager;
import java.util.logging.Logger;
import java.util.logging.LoggingMXBean;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.google.common.collect.Lists;
import com.google.common.collect.Ordering;
import com.google.inject.Inject;

import org.antlr.stringtemplate.StringTemplate;
import org.apache.commons.lang.StringUtils;

import com.twitter.common.base.Closure;

/**
 * Servlet that allows for dynamic adjustment of the logging configuration.
 *
 * @author William Farner
 */
public class LogConfig extends StringTemplateServlet {
    private static final List<String> LOG_LEVELS = Lists.newArrayList(Level.SEVERE.getName(),
            Level.WARNING.getName(), Level.INFO.getName(), Level.CONFIG.getName(), Level.FINE.getName(),
            Level.FINER.getName(), Level.FINEST.getName(), "INHERIT" // Display value for a null level, the logger inherits from its ancestor.
    );

    @Inject
    public LogConfig(@CacheTemplates boolean cacheTemplates) {
        super("logconfig", cacheTemplates);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        displayPage(req, resp, true);
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        displayPage(req, resp, false);
    }

    protected void displayPage(final HttpServletRequest req, HttpServletResponse resp, final boolean posted)
            throws ServletException, IOException {
        writeTemplate(resp, new Closure<StringTemplate>() {
            @Override
            public void execute(StringTemplate stringTemplate) {
                LoggingMXBean logBean = LogManager.getLoggingMXBean();

                if (posted) {
                    String loggerName = req.getParameter("logger");
                    String loggerLevel = req.getParameter("level");
                    if (loggerName != null && loggerLevel != null) {
                        Logger logger = Logger.getLogger(loggerName);
                        Level newLevel = loggerLevel.equals("INHERIT") ? null : Level.parse(loggerLevel);
                        logger.setLevel(newLevel);
                        if (newLevel != null) {
                            maybeAdjustHandlerLevels(logger, newLevel);
                        }

                        stringTemplate.setAttribute("configChange",
                                String.format("%s level changed to %s", loggerName, loggerLevel));
                    }
                }

                List<LoggerConfig> loggerConfigs = Lists.newArrayList();
                for (String logger : Ordering.natural().immutableSortedCopy(logBean.getLoggerNames())) {
                    loggerConfigs.add(new LoggerConfig(logger, logBean.getLoggerLevel(logger)));
                }

                stringTemplate.setAttribute("loggers", loggerConfigs);
                stringTemplate.setAttribute("levels", LOG_LEVELS);
            }
        });
    }

    private void maybeAdjustHandlerLevels(Logger logger, Level newLevel) {
        do {
            for (Handler handler : logger.getHandlers()) {
                Level handlerLevel = handler.getLevel();
                if (newLevel.intValue() < handlerLevel.intValue()) {
                    handler.setLevel(newLevel);
                }
            }
        } while (logger.getUseParentHandlers() && (logger = logger.getParent()) != null);
    }

    private class LoggerConfig {
        private final String name;
        private final String level;

        public LoggerConfig(String name, String level) {
            this.name = name;
            this.level = StringUtils.isBlank(level) ? "INHERIT" : level;
        }

        public String getName() {
            return name;
        }

        public String getLevel() {
            return level;
        }
    }
}