filecontext.java

hadoop:Nutch集群平台

/*
 * FileContext.java
 *
 * Copyright 2006 The Apache Software Foundation
 *
 * Licensed 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.metrics.file;

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Iterator;
import org.apache.hadoop.metrics.ContextFactory;
import org.apache.hadoop.metrics.MetricsException;
import org.apache.hadoop.metrics.spi.AbstractMetricsContext;
import org.apache.hadoop.metrics.spi.OutputRecord;

/**
 * Metrics context for writing metrics to a file.<p/>
 *
 * This class is configured by setting ContextFactory attributes which in turn
 * are usually configured through a properties file.  All the attributes are
 * prefixed by the contextName. For example, the properties file might contain:
 * <pre>
 * myContextName.fileName=/tmp/metrics.log
 * myContextName.period=5
 * </pre>
 *
 */
public class FileContext extends AbstractMetricsContext {
    
    /* Configuration attribute names */
    protected static final String FILE_NAME_PROPERTY = "fileName";
    protected static final String PERIOD_PROPERTY = "period";
    
    private File file = null;              // file for metrics to be written to
    private PrintWriter writer = null;
    
    /** Creates a new instance of FileContext */
    public FileContext() {}
    
    public void init(String contextName, ContextFactory factory) {
        super.init(contextName, factory);
        
        String fileName = getAttribute(FILE_NAME_PROPERTY);
        if (fileName != null) {
            file = new File(fileName);
        }
        
        String periodStr = getAttribute(PERIOD_PROPERTY);
        if (periodStr != null) {
            int period = 0;
            try {
                period = Integer.parseInt(periodStr);
            } catch (NumberFormatException nfe) {
            }
            if (period <= 0) {
                throw new MetricsException("Invalid period: " + periodStr);
            }
            setPeriod(period);
        }
    }

    /**
     * Returns the configured file name, or null.
     */
    public String getFileName() {
        if (file == null) {
            return null;
        } else {
            return file.getName();
        }
    }
    
    /**
     * Starts or restarts monitoring, by opening in append-mode, the
     * file specified by the <code>fileName</code> attribute,
     * if specified. Otherwise the data will be written to standard
     * output.
     */
    public void startMonitoring()
        throws IOException 
    {
        if (file == null) {
            writer = new PrintWriter(new BufferedOutputStream(System.out));
        } else {
            writer = new PrintWriter(new FileWriter(file, true));
        }
        super.startMonitoring();
    }
    
    /**
     * Stops monitoring, closing the file.
     * @see #close()
     */
    public void stopMonitoring() {
        super.stopMonitoring();
        
        if (writer != null) {
            writer.close();
            writer = null;
        }
    }
    
    /**
     * Emits a metrics record to a file.
     */
    public void emitRecord(String contextName, String recordName, OutputRecord outRec) {
        writer.print(contextName);
        writer.print(".");
        writer.print(recordName);
        String separator = ": ";
        // for (String tagName : outRec.getTagNames()) {
        Iterator tagIt = outRec.getTagNames().iterator();
        while (tagIt.hasNext()) {
            String tagName = (String) tagIt.next();
            writer.print(separator);
            separator = ", ";
            writer.print(tagName);
            writer.print("=");
            writer.print(outRec.getTag(tagName));
        }
        // for (String metricName : outRec.getMetricNames()) {
        Iterator metricIt = outRec.getMetricNames().iterator();
        while (metricIt.hasNext()) {
            String metricName = (String) metricIt.next();
            writer.print(separator);
            separator = ", ";
            writer.print(metricName);
            writer.print("=");
            writer.print(outRec.getMetric(metricName));
        }
        writer.println();
    }
    
    /**
     * Flushes the output writer, forcing updates to disk.
     */
    public void flush() {
        writer.flush();
    }
}