com.cloudera.oryx.common.log.MemoryHandler.java Source code

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Here is the source code for com.cloudera.oryx.common.log.MemoryHandler.java

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/*
 * Copyright (c) 2013, Cloudera, Inc. All Rights Reserved.
 *
 * Cloudera, 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
 *
 * This software 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.cloudera.oryx.common.log;

import java.util.Queue;
import java.util.logging.Handler;
import java.util.logging.Level;
import java.util.logging.LogRecord;
import java.util.logging.SimpleFormatter;

import com.google.common.collect.Lists;

/**
 * Simple {@link Handler} that records recent log lines in memory.
 * 
 * @author Sean Owen
 */
public final class MemoryHandler extends Handler {

    private static final int NUM_LINES = 1000;
    private static final String JAVA7_LOG_FORMAT_PROP = "java.util.logging.SimpleFormatter.format";

    private final Queue<String> logLines;

    public MemoryHandler() {
        logLines = Lists.newLinkedList();
        setFormatter(new SimpleFormatter());
        setLevel(Level.FINE);
    }

    /**
     * @return recent log lines
     */
    public Iterable<String> getLogLines() {
        return logLines;
    }

    @Override
    public void publish(LogRecord logRecord) {
        String line = getFormatter().format(logRecord);
        synchronized (logLines) {
            logLines.add(line);
            for (int i = 0; i < logLines.size() - NUM_LINES; i++) {
                logLines.remove();
            }
        }
    }

    @Override
    public void flush() {
    }

    @Override
    public void close() {
        logLines.clear();
    }

    /**
     * <p>Sets the {@code java.util.logging} default output format to something more sensible than the 2-line default.
     * This can be overridden further on the command line. The format is like:</p>
     *
     * <p><pre>
     * Mon Nov 26 23:16:09 GMT 2012 INFO Starting service Tomcat
     * </pre></p>
     */
    public static void setSensibleLogFormat() {
        if (System.getProperty(JAVA7_LOG_FORMAT_PROP) == null) {
            System.setProperty(JAVA7_LOG_FORMAT_PROP, "%1$tc %4$s %5$s%6$s%n");
        }
        // Note that this above is a Java system property, not our app config
    }

}