com.odiago.flumebase.util.AppUtils.java Source code

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Here is the source code for com.odiago.flumebase.util.AppUtils.java

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/**
 * Licensed to Odiago, Inc. under one or more contributor license
 * agreements.  See the NOTICE.txt file distributed with this work for
 * additional information regarding copyright ownership.  Odiago, Inc.
 * 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 com.odiago.flumebase.util;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

import java.util.Properties;

import org.apache.hadoop.conf.Configuration;

import org.apache.hadoop.fs.Path;

import org.apache.log4j.PropertyConfigurator;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Utility methods regarding application lifecycle management (startup,
 * logging init, etc.)
 */
public final class AppUtils {
    private static final Logger LOG = LoggerFactory.getLogger(AppUtils.class.getName());

    /** System property that sets the path of the FlumeBase configuration. */
    private static final String FLUMEBASE_CONF_DIR_KEY = "flumebase.conf.dir";

    /** Environment variable that sets the path of the FlumeBase configuration. */
    private static final String FLUMEBASE_CONF_DIR_ENV = "FLUMEBASE_CONF_DIR";

    /** Environment variable that sets the path of the FlumeBase installation "home". */
    private static final String FLUMEBASE_HOME_ENV = "FLUMEBASE_HOME";

    private AppUtils() {
    }

    /**
     * Initialize slf4j / log4j for the application.
     */
    public static void initLogging() {
        String confDir = getAppConfDir();
        File confDirFile = new File(confDir);
        File log4jPropertyFile = new File(confDirFile, "log4j.properties");
        FileInputStream fis = null;
        try {
            // Load the properties from the file first.
            fis = new FileInputStream(log4jPropertyFile);
            Properties props = new Properties();
            props.load(fis);

            // Overlay the system properties on top of the file, in case the
            // user wants to override the file settings at invocation time.
            Properties sysProps = System.getProperties();
            props.putAll(sysProps);
            PropertyConfigurator.configure(props);
            LOG.debug("Logging enabled.");
        } catch (IOException ioe) {
            System.err.println("IOException encoutered while initializing logging.");
            System.err.println("The logging system might not be ready, meaning you");
            System.err.println("might miss many other messages. Do you have an");
            System.err.println("etc/log4j.properties file in this installation?");
            System.err.println("Specific exception follows:");
            System.err.println(ioe);
        } finally {
            if (null != fis) {
                try {
                    fis.close();
                } catch (IOException ioe) {
                    LOG.warn("Exception closing log4j.properties file: " + ioe);
                }
            }
        }
    }

    /**
     * @return the home directory for this application installation.
     * This is taken from $FLUMEBASE_HOME. Returns null if this is not set.
     */
    public static String getAppHomeDir() {
        String homeEnv = System.getenv(FLUMEBASE_HOME_ENV);
        if (null != homeEnv) {
            File homeFile = new File(homeEnv);
            return homeFile.getAbsolutePath();
        } else {
            return null;
        }
    }

    /**
     * @return the configuration directory for this application.
     * This is one of the following, in order:
     * <ol>
     *   <li>${flumebase.conf.dir} (System property)</li>
     *   <li>$FLUMEBASE_CONF_DIR</li>
     *   <li>$FLUMEBASE_HOME/etc</li>
     *   <li>(current dir)</li>
     * </ol>
     */
    public static String getAppConfDir() {
        String flumebaseConfDir = System.getProperty(FLUMEBASE_CONF_DIR_KEY, null);
        if (null == flumebaseConfDir) {
            flumebaseConfDir = System.getenv(FLUMEBASE_CONF_DIR_ENV);
        }

        if (null != flumebaseConfDir) {
            File confFile = new File(flumebaseConfDir);
            return confFile.getAbsolutePath();
        }

        // Infer from application home dir. 
        String homeDir = getAppHomeDir();
        if (null != homeDir) {
            // return $FLUMEBASE_HOME/etc.
            File homeFile = new File(homeDir);
            return new File(homeFile, "etc").getAbsolutePath();
        }

        return ".";
    }

    /**
     * @return a Configuration with the appropriate flumebase-site.xml file added.
     * Should be used as the base Configuration for the program.
     */
    public static Configuration initConfResources() {
        String flumebaseConfFile = new File(getAppConfDir(), "flumebase-site.xml").toString();
        LOG.debug("Initializing configuration from " + flumebaseConfFile);
        Configuration conf = new Configuration();
        conf.addResource(new Path(flumebaseConfFile));
        return conf;
    }
}